freepascal.compiler/compiler/ogbase.pas

{
    Copyright (c) 1998-2006 by Peter Vreman

    Contains the base stuff for binary object file writers

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 ****************************************************************************
}
unit ogbase;

{$i fpcdefs.inc}

interface

    uses
      { common }
      cutils,
      cclasses,
      { targets }
      systems,globtype,
      { outputwriters }
      owbase,
      { assembler }
      aasmbase,
      cpuinfo;

    type
      TObjSection = class;
      TObjData = class;

      TExeSection = class;
      TExeSymbol  = class;
      TExeOutput  = class;

      TObjRelocationType = (
         { Relocation to absolute address }
         RELOC_ABSOLUTE,
{$ifdef x86_64}
         { 32bit Relocation to absolute address }
         RELOC_ABSOLUTE32,
         { 64 bit coff only }
         RELOC_RELATIVE_1,
         RELOC_RELATIVE_2,
         RELOC_RELATIVE_3,
         RELOC_RELATIVE_4,
         RELOC_RELATIVE_5,
         { PIC }
         RELOC_GOTPCREL,
         RELOC_GOTPCRELX,
         RELOC_REX_GOTPCRELX,
         RELOC_PLT32,
         RELOC_TLSGD,
         RELOC_TPOFF,
{$endif x86_64}
{$ifdef i386}
         { PIC }
         RELOC_GOTPC,
         RELOC_GOT32,
         RELOC_PLT32,
         RELOC_TLSGD,
         RELOC_NTPOFF,
{$endif i386}
{$ifdef i8086}
         RELOC_ABSOLUTE32,
         RELOC_RELATIVE32,
         RELOC_FARPTR,
         RELOC_FARPTR_RELATIVEOFFSET,
         RELOC_FARPTR48,
         RELOC_FARPTR48_RELATIVEOFFSET,
         RELOC_SEG,
         RELOC_SEGREL,
         RELOC_DGROUP,
         RELOC_DGROUPREL,
         RELOC_FARDATASEG,
         RELOC_FARDATASEGREL,
{$endif i8086}
{$ifdef arm}
         RELOC_RELATIVE_24,
         RELOC_RELATIVE_CALL,
         RELOC_RELATIVE_24_THUMB,
         RELOC_RELATIVE_CALL_THUMB,
         RELOC_GOT32,
         RELOC_TPOFF,
         RELOC_TLSGD,
         RELOC_TLSDESC,
         RELOC_TLS_CALL,
         RELOC_ARM_CALL,
{$endif arm}
{$ifdef aarch64}
         RELOC_ABSOLUTE32,
         RELOC_RELATIVE_26,
         RELOC_RELATIVE_19,
         RELOC_ADR_PREL_LO21,
         RELOC_ADR_PREL_PG_HI21,
         RELOC_ADD_ABS_LO12,
         RELOC_LDST8_ABS_LO12,
{$endif aarch64}
{$ifdef z80}
         RELOC_ABSOLUTE_HI8,
         RELOC_ABSOLUTE_LO8,
{$endif z80}
{$ifdef WASM32}
         RELOC_FUNCTION_INDEX_LEB,
         RELOC_MEMORY_ADDR_LEB,
         RELOC_MEMORY_ADDR_OR_TABLE_INDEX_SLEB,
         RELOC_TYPE_INDEX_LEB,
         RELOC_GLOBAL_INDEX_LEB,
         RELOC_TAG_INDEX_LEB,
{$endif WASM32}
         { Relative relocation }
         RELOC_RELATIVE,
         { PECoff (Windows) RVA relocation }
         RELOC_RVA,
         { PECoff (Windows) section relocation, required by DWARF2 debug info }
         RELOC_SECREL32,
         { Generate a 0 value at the place of the relocation,
           this is used to remove unused vtable entries }
         RELOC_ZERO,
         { No relocation is needed. It is used in ARM object files.
           Also internal linker use this reloc to make virtual (not real)
           links to some sections }
         RELOC_NONE,
         { Darwin relocation, using PAIR }
         RELOC_PIC_PAIR,
         { Relative to GOT/gp }
         RELOC_GOTOFF,
         { Untranslated target-specific value }
         RELOC_RAW,
         { offset in TLS block }
         RELOC_DTPOFF
      );

{$if defined(x86_64) or defined(aarch64)}
    { no special aliases for x86_64 }
{$elseif defined(i8086)}
    const
      RELOC_ABSOLUTE16 = RELOC_ABSOLUTE;
      RELOC_RELATIVE16 = RELOC_RELATIVE;
{$else}
    const
      RELOC_ABSOLUTE32 = RELOC_ABSOLUTE;
{$endif}

    const
      { stab types }
      N_GSYM = $20;
      N_STSYM = 38;     { initialized const }
      N_LCSYM = 40;     { non initialized variable}
      N_Function = $24; { function or const }
      N_TextLine = $44;
      N_DataLine = $46;
      N_BssLine = $48;
      N_RSYM = $40;     { register variable }
      N_LSYM = $80;
      N_tsym = 160;
      N_SourceFile = $64;
      N_IncludeFile = $84;
      N_BINCL = $82;
      N_EINCL = $A2;
      N_LBRAC = $C0;
      N_EXCL  = $C2;
      N_RBRAC = $E0;

      { GNU extensions }
      debuglinkname='.gnu_debuglink';

      { TObjRelocation.flags }
      { 'ftype' field contains platform-specific value }
      rf_raw = 1;
      { relocation must be added to dynamic list }
      rf_dynamic = 2;
      { relocation target is absent/irrelevant (e.g. R_ARM_V4BX) }
      rf_nosymbol = 4;

    type
      TObjSectionOption = (
       { Has Data available in the file }
       oso_Data,
       { Is loaded into memory }
       oso_load,
       { Writable }
       oso_write,
       { Contains executable instructions }
       oso_executable,
       { Never discard section }
       oso_keep,
       { Procedure Linkage Table specific treatment }
       oso_plt,
       { Contains debug info and can be stripped }
       oso_debug,
       { Contains only strings }
       oso_strings,
       { Must be cloned when writing separate debug file }
       oso_debug_copy,
       { Has relocations with explicit addends (ELF-specific) }
       oso_rela_relocs,
       { Supports bss-like allocation of data, even though it is written in file (i.e. also has oso_Data) }
       oso_sparse_data,
       { Section to support the resolution of multiple symbols with the same name }
       oso_comdat,
       { section containing thread variables }
       oso_threadvar,
       { being a notes section }
       oso_note,
       { arm attributes section }
       oso_arm_attributes
     );

     TObjSectionOptions = set of TObjSectionOption;

     TObjSectionComdatSelection = (
       { Section is not a COMDAT section }
       oscs_none,
       { Select any of the symbols }
       oscs_any,
       { Select any symbol, but abort if they differ in size }
       oscs_same_size,
       { Select any symbol, but abort if they differ in size or content }
       oscs_exact_match,
       { Select the symbol only if the associated symbol is linked as well }
       oscs_associative,
       { Select the largest symbol }
       oscs_largest
     );

{$ifdef i8086}
     { allow 32-bit sections on i8086. Useful for the dwarf debug info, as well
       as to allow linking 32-bit obj modules. }
     TObjSectionOfs = LongWord;
{$else i8086}
     TObjSectionOfs = PUInt;
{$endif i8086}

     TObjSectionGroup = class;

     TObjSymbol = class(TFPHashObject)
     public
       bind       : TAsmsymbind;
       typ        : TAsmsymtype;
       { Current assemble pass, used to detect duplicate labels }
       pass       : byte;
       { how the symbol is referenced (target-specific bitfield) }
       refs       : byte;
       symidx     : longint;
       objsection : TObjSection;
       offset,
       size       : TObjSectionOfs;
       { Used for external and common solving during linking }
       exesymbol  : TExeSymbol;

       { Darwin asm is using indirect symbols resolving }
       indsymbol  : TObjSymbol;

       { Used by the OMF object format and its complicated relocation records }
       group: TObjSectionGroup;
{$ifdef ARM}
       ThumbFunc : boolean;
{$endif ARM}

       constructor create(AList:TFPHashObjectList;const AName:string);virtual;
       function  ToString:ansistring;override;
       function  address:qword;
       procedure SetAddress(apass:byte;aobjsec:TObjSection;abind:TAsmsymbind;atyp:Tasmsymtype);
       function  ObjData: TObjData;
       { string representation for the linker map file }
       function  AddressStr(AImageBase: qword): string;virtual;
     end;
     TObjSymbolClass = class of TObjSymbol;

     { Stabs is common for all targets }
     TObjStabEntry=packed record
        strpos  : longint;
        ntype   : byte;
        nother  : byte;
        ndesc   : word;
        nvalue  : longint;
     end;
     PObjStabEntry=^TObjStabEntry;

     TObjRelocation = class
     private
        function GetType:TObjRelocationType;
        procedure SetType(v:TObjRelocationType);
     public
        DataOffset,
        orgsize    : TObjSectionOfs;  { COFF: original size of the symbol to relocate }
                                      { ELF: explicit addend }
        symbol     : TObjSymbol;
        objsection : TObjSection; { only used if symbol=nil }
        group      : TObjSectionGroup; { only used if symbol=nil and objsection=nil }
        ftype      : byte;
        size       : byte;
        flags      : byte;
        constructor CreateSymbol(ADataOffset:TObjSectionOfs;s:TObjSymbol;Atyp:TObjRelocationType);
        constructor CreateSection(ADataOffset:TObjSectionOfs;aobjsec:TObjSection;Atyp:TObjRelocationType);
        constructor CreateGroup(ADataOffset:TObjSectionOfs;grp:TObjSectionGroup;Atyp:TObjRelocationType);
        constructor CreateRaw(ADataOffset:TObjSectionOfs;s:TObjSymbol;ARawType:byte);
        function TargetName:TSymStr;
        function ToString: ansistring; override;
        property typ: TObjRelocationType read GetType write SetType;
     end;

     TObjSection = class(TFPHashObject)
     private
       FData       : TDynamicArray;
       FSecOptions : TObjSectionOptions;
       FCachedFullName : pshortstring;
       FSizeLimit : TObjSectionOfs;
       procedure SetSecOptions(Aoptions:TObjSectionOptions);
       procedure SectionTooLargeError;
     protected
       function GetAltName: string; virtual;
     public
       ObjData    : TObjData;
       index      : longword;  { index of section in section headers }
       SecSymIdx  : longint;   { index for the section in symtab }
       SecAlign   : longint;   { alignment of the section }
       { section Data }
       Size,
       DataPos    : TObjSectionOfs;
       MemPos     : qword;
       Group      : TObjSectionGroup;
       AssociativeSection : TObjSection;
       ComdatSelection : TObjSectionComdatSelection;
       DataAlignBytes : shortint;
       { Relocations (=references) to other sections }
       ObjRelocations : TFPObjectList;
       { executable linking }
       ExeSection  : TExeSection;
       USed        : Boolean;
       VTRefList : TFPObjectList;
       constructor create(AList:TFPHashObjectList;const Aname:string;Aalign:longint;Aoptions:TObjSectionOptions);virtual;
       destructor  destroy;override;
       function  ToString:ansistring;override;
       function  write(const d;l:TObjSectionOfs):TObjSectionOfs;
       procedure writeInt8(v: int8);
       procedure writeInt16LE(v: int16);
       procedure writeInt16BE(v: int16);
       procedure writeInt32LE(v: int32);
       procedure writeInt32BE(v: int32);
       procedure writeInt64LE(v: int64);
       procedure writeInt64BE(v: int64);
       procedure writeUInt8(v: uint8);
       procedure writeUInt16LE(v: uint16);
       procedure writeUInt16BE(v: uint16);
       procedure writeUInt32LE(v: uint32);
       procedure writeUInt32BE(v: uint32);
       procedure writeUInt64LE(v: uint64);
       procedure writeUInt64BE(v: uint64);
       { writes string plus zero byte }
       function  writestr(const s:string):TObjSectionOfs;
       function  WriteZeros(l:longword):TObjSectionOfs;
       { writes content of s without null termination }
       function  WriteBytes(const s:string):TObjSectionOfs;
       procedure writeReloc_internal(aTarget:TObjSection;offset:aword;len:byte;reltype:TObjRelocationType);virtual;
       function  setmempos(mpos:qword):qword;
       procedure setDatapos(var dpos:TObjSectionOfs);
       procedure alloc(l:TObjSectionOfs);
       procedure addsymReloc(ofs:TObjSectionOfs;p:TObjSymbol;Reloctype:TObjRelocationType);
       procedure addsectionReloc(ofs:TObjSectionOfs;aobjsec:TObjSection;Reloctype:TObjRelocationType);
       procedure addrawReloc(ofs:TObjSectionOfs;p:TObjSymbol;RawReloctype:byte);
       procedure ReleaseData;
       function  FullName:string;
       { string representation for the linker map file }
       function  MemPosStr(AImageBase: qword): string;virtual;
       property  Data:TDynamicArray read FData;
       property  SecOptions:TObjSectionOptions read FSecOptions write SetSecOptions;
       property  SizeLimit:TObjSectionOfs read FSizeLimit write FSizeLimit;
     end;
     TObjSectionClass = class of TObjSection;

     TObjSectionGroup = class(TFPHashObject)
     public
       index: longword;  { index of group in group headers }
       members: array of TObjSection;
       iscomdat: boolean;
     end;
     TObjSectionGroupClass = class of TObjSectionGroup;

     TString80 = string[80];

     TObjSymbolList = class(TFPHashObjectList)
     public
       Owner: TObjData;
     end;

{$if defined(i8086)}
     { on i8086 we use a longint, to support 32-bit relocations as well (e.g.
       for allowing 386+ instructions with 32-bit addresses in inline asm code) }
     TRelocDataInt = longint;
{$elseif defined(cpu16bitaddr)}
     TRelocDataInt = asizeint;
{$else}
     TRelocDataInt = aint;
{$endif}

     TObjData = class(TLinkedListItem)
     private
       FCurrObjSec : TObjSection;
       FObjSectionList  : TFPHashObjectList;
       FCObjSymbol      : TObjSymbolClass;
       FCObjSection     : TObjSectionClass;
       FCObjSectionGroup: TObjSectionGroupClass;
       { Symbols that will be defined in this object file }
       FObjSymbolList    : TObjSymbolList;
       FCachedAsmSymbolList : TFPObjectList;
       { Special info sections that are written to during object generation }
       FStabsObjSec,
       FStabStrObjSec : TObjSection;
       FGroupsList : TFPHashObjectList;
       FCPUType : tcputype;
       procedure section_reset(p:TObject;arg:pointer);
       procedure section_afteralloc(p:TObject;arg:pointer);
       procedure section_afterwrite(p:TObject;arg:pointer);
     protected
       FName       : TString80;
       property CObjSection:TObjSectionClass read FCObjSection write FCObjSection;
       property CObjSectionGroup: TObjSectionGroupClass read FCObjSectionGroup write FCObjSectionGroup;
     public
       CurrPass  : byte;
       ExecStack : boolean;
{$ifdef ARM}
       ThumbFunc : boolean;
{$endif ARM}
       constructor create(const n:string);virtual;
       destructor  destroy;override;
       { Sections }
       function  sectionname(atype:TAsmSectiontype;const aname:string;aorder:TAsmSectionOrder):string;virtual;abstract;
       class function sectiontype2options(atype:TAsmSectiontype):TObjSectionOptions;
       function  sectiontype2align(atype:TAsmSectiontype):longint;virtual;
       class procedure sectiontype2progbitsandflags(atype:TAsmSectiontype;out progbits:TSectionProgbits;out flags:TSectionFlags);virtual;
       function  createsection(atype:TAsmSectionType;const aname:string='';aorder:TAsmSectionOrder=secorder_default):TObjSection;virtual;
       function  createsection(atype:TAsmSectionType;secflags:TSectionFlags;aprogbits:TSectionProgbits;const aname:string='';aorder:TAsmSectionOrder=secorder_default):TObjSection;virtual;
       function  createsection(const aname:string;aalign:longint;aoptions:TObjSectionOptions;DiscardDuplicate:boolean=true):TObjSection;virtual;
       function  createsectiongroup(const aname:string):TObjSectionGroup;
       procedure CreateDebugSections;virtual;
       function  findsection(const aname:string):TObjSection;
       procedure setsection(asec:TObjSection);
       { Symbols }
       function  createsymbol(const aname:string):TObjSymbol;
       function  symboldefine(asmsym:TAsmSymbol):TObjSymbol;
       function  symboldefine(const aname:string;abind:TAsmsymbind;atyp:Tasmsymtype):TObjSymbol;
       function  symbolref(asmsym:TAsmSymbol):TObjSymbol;
       function  symbolref(const aname:string):TObjSymbol;
       procedure symbolpairdefine(akind: TSymbolPairKind;const asym, avalue: string);virtual;
       procedure ResetCachedAsmSymbols;
       { Allocation }
       procedure alloc(len:TObjSectionOfs);
       procedure allocalign(len:longint);
       procedure writebytes(const Data;len:TObjSectionOfs);
       procedure writebytes(const Data : TByteDynArray;len:TObjSectionOfs);
       procedure writebytes(const Data : TAnsiCharDynArray;len:TObjSectionOfs);
       procedure writeInt8(v: int8);
       procedure writeInt16LE(v: int16);
       procedure writeInt16BE(v: int16);
       procedure writeInt32LE(v: int32);
       procedure writeInt32BE(v: int32);
       procedure writeInt64LE(v: int64);
       procedure writeInt64BE(v: int64);
       procedure writeUInt8(v: uint8);
       procedure writeUInt16LE(v: uint16);
       procedure writeUInt16BE(v: uint16);
       procedure writeUInt32LE(v: uint32);
       procedure writeUInt32BE(v: uint32);
       procedure writeUInt64LE(v: uint64);
       procedure writeUInt64BE(v: uint64);
       procedure writeReloc(Data:TRelocDataInt;len:aword;p:TObjSymbol;Reloctype:TObjRelocationType);virtual;abstract;
       procedure beforealloc;virtual;
       procedure beforewrite;virtual;
       procedure afteralloc;virtual;
       procedure afterwrite;virtual;
       procedure resetsections;
       procedure layoutsections(var datapos:TObjSectionOfs);
       property Name:TString80 read FName;
       property CurrObjSec:TObjSection read FCurrObjSec;
       property ObjSymbolList:TObjSymbolList read FObjSymbolList;
       property ObjSectionList:TFPHashObjectList read FObjSectionList;
       property GroupsList:TFPHashObjectList read FGroupsList;
       property StabsSec:TObjSection read FStabsObjSec write FStabsObjSec;
       property StabStrSec:TObjSection read FStabStrObjSec write FStabStrObjSec;
       property CObjSymbol: TObjSymbolClass read FCObjSymbol write FCObjSymbol;
       { Current CPU type for the internal asm writer.
         Instructions, not supported by the given CPU should produce an error.
         A value of 'cpu_none' means no restrictions (all instructions should be accepted) }
       property CPUType : tcputype read FCPUType write FCPUType;
     end;
     TObjDataClass = class of TObjData;

     TObjOutput = class
      private
        FCObjData : TObjDataClass;
      protected
        { writer }
        FWriter    : TObjectwriter;
        function  writeData(Data:TObjData):boolean;virtual;abstract;
        property CObjData : TObjDataClass read FCObjData write FCObjData;
        procedure WriteSectionContent(Data:TObjData);
      public
        constructor create(AWriter:TObjectWriter);virtual;
        destructor  destroy;override;
        function  newObjData(const n:string):TObjData;
        function  startObjectfile(const fn:string):boolean;
        function  writeobjectfile(Data:TObjData):boolean;
        procedure exportsymbol(p:TObjSymbol);
        property Writer:TObjectWriter read FWriter;
      end;
      TObjOutputClass=class of TObjOutput;

      TObjInput = class
      private
        FCObjData : TObjDataClass;
      protected
        { reader }
        FReader    : TObjectReader;
        InputFileName : string;
        property CObjData : TObjDataClass read FCObjData write FCObjData;
        procedure ReadSectionContent(Data:TObjData);
      public
        constructor create;virtual;
        function  ReadObjData(AReader:TObjectreader;out Data:TObjData):boolean;virtual;abstract;
        class function CanReadObjData(AReader:TObjectreader):boolean;virtual;
        procedure inputerror(const s : string);
      end;
      TObjInputClass=class of TObjInput;

      TVTableEntry=record
        ObjRelocation : TObjRelocation;
        orgreloctype,
        orgrelocflags : byte;
        Enabled,
        Used  : Boolean;
      end;
      PVTableEntry=^TVTableEntry;

      TExeVTable = class
      private
        procedure CheckIdx(VTableIdx:longint);
      public
        ExeSymbol    : TExeSymbol;
        EntryCnt     : Longint;
        EntryArray   : PVTableEntry;
        Consolidated : Boolean;
        ChildList    : TFPObjectList;
        constructor Create(AExeSymbol:TExeSymbol);
        destructor Destroy;override;
        procedure AddChild(vt:TExeVTable);
        procedure AddEntry(VTableIdx:Longint);
        procedure SetVTableSize(ASize:longint);
        function  VTableRef(VTableIdx:Longint):TObjRelocation;
      end;

      TSymbolState = (
        symstate_undefined,
        symstate_undefweak,  // undefined but has only weak refs - don't complain
        symstate_defined,
        symstate_defweak,
        symstate_common,
        symstate_dynamic     // a matching symbol has been seen in .so
      );

      TExeSymbol = class(TFPHashObject)
        ObjSymbol  : TObjSymbol;
        State      : TSymbolState;
        used       : boolean;
        { Used for vmt references optimization }
        VTable     : TExeVTable;
        { fields for ELF linking }
        gotoffset  : aword;
        dynindex   : aword;
        { A thunk used to redirect some references to symbol (like absolute
          jumps/calls to PIC code).
          This probably is also needed for ARM/Thumb interworking and alike.
          TODO: consider reusing objsymbol.indsymbol for this purpose }
{$ifdef mips}
        stubsymbol : TObjSymbol;
{$endif mips}
      end;

      TExeSection = class(TFPHashObject)
      private
        FSecSymIdx : longint;
        FObjSectionList : TFPObjectList;
      public
        Size,
        DataPos,
        MemPos     : qword;
        SecAlign   : longint;
        Disabled   : boolean;
        SecOptions : TObjSectionOptions;
        constructor create(AList:TFPHashObjectList;const AName:string);virtual;
        destructor  destroy;override;
        procedure AddObjSection(objsec:TObjSection;ignoreprops:boolean=false);virtual;
        { string representation for the linker map file }
        function MemPosStr(AImageBase: qword): string;virtual;
        property ObjSectionList:TFPObjectList read FObjSectionList;
        property SecSymIdx:longint read FSecSymIdx write FSecSymIdx;
      end;
      TExeSectionClass=class of TExeSection;

      TlibKind = (lkArchive,lkObject,lkGroup);

      TStaticLibrary = class(TObject)
      private
        FName : TCmdStr;
        FPayload : TObject;                 { lkArchive: TObjectReader }
                                            { lkObject:  TObjData      }
                                            { lkGroup:   TFPObjectList }
        FObjInputClass : TObjInputClass;
        FKind: TlibKind;
        FAsNeeded : Boolean;
        function GetArReader:TObjectReader;
        function GetGroupMembers:TFPObjectList;
        function GetObjData:TObjData;
      public
        constructor create(const AName:TCmdStr;AReader:TObjectReader;AObjInputClass:TObjInputClass);
        constructor create_object(AObjData:TObjData);
        constructor create_group;
        destructor  destroy;override;
        property ArReader:TObjectReader read GetArReader;
        property ObjInputClass:TObjInputClass read FObjInputClass;
        property GroupMembers:TFPObjectList read GetGroupMembers;
        property ObjData:TObjData read GetObjData;
        property AsNeeded:Boolean read FAsNeeded write FAsNeeded;
        property Kind:TLibKind read FKind;
      end;

      TImportLibrary = class(TFPHashObject)
      private
        FImportSymbolList : TFPHashObjectList;
      public
        constructor create(AList:TFPHashObjectList;const AName:string);
        destructor  destroy;override;
        property ImportSymbolList:TFPHashObjectList read FImportSymbolList;
      end;

      TImportSymbol = class(TFPHashObject)
      private
        FOrdNr  : longint;
        FIsVar  : boolean;
        FMangledName : string;
        FCachedExeSymbol: TExeSymbol;
      public
        constructor create(AList:TFPHashObjectList;const AName,AMangledName:string;AOrdNr:longint;AIsVar:boolean);
        property OrdNr: longint read FOrdNr;
        property MangledName: string read FMangledName;
        property IsVar: boolean read FIsVar;
        property CachedExeSymbol: TExeSymbol read FCachedExeSymbol write FCachedExeSymbol;
      end;

      TExeWriteMode = (ewm_exefull,ewm_dbgonly,ewm_exeonly);

      TExeOutput = class
      private
        { ExeSectionList }
        FCObjSymbol       : TObjSymbolClass;
        FCObjData         : TObjDataClass;
        FCExeSection      : TExeSectionClass;
        FCurrExeSec       : TExeSection;
        FExeSectionList   : TFPHashObjectList;
        Fzeronr           : longint;
        Fvaluesnr         : longint;
        { Symbols }
        FExeSymbolList    : TFPHashObjectList;
        FUnresolvedExeSymbols : TFPObjectList;
        FExternalObjSymbols,
        FCommonObjSymbols   : TFPObjectList;
        FProvidedObjSymbols : TFPObjectList;
        FIndirectObjSymbols : TFPObjectList;
        FEntryName          : string;
        FExeVTableList     : TFPObjectList;
        { Objects }
        FObjDataList  : TFPObjectList;
        { Position calculation }
        FImageBase    : qword;
        FCurrMemPos       : qword;
        procedure SetCurrMemPos(const AValue: qword);
      protected
        { writer }
        FExeWriteMode : TExeWriteMode;
        FWriter : TObjectwriter;
        commonObjSection : TObjSection;
        internalObjData : TObjData;
        EntrySym  : TObjSymbol;
        SectionDataAlign,
        SectionMemAlign : aword;
        ComdatGroups : TFPHashList;
        FixedSectionAlign : boolean;
        AllowUndefinedSymbols : boolean;
        function  writeData:boolean;virtual;abstract;
        property CExeSection:TExeSectionClass read FCExeSection write FCExeSection;
        property CObjData:TObjDataClass read FCObjData write FCObjData;
        property CObjSymbol:TObjSymbolClass read FCObjSymbol write FCObjSymbol;
        procedure Order_ObjSectionList(ObjSectionList : TFPObjectList; const aPattern:string);virtual;
        procedure WriteExeSectionContent;
        procedure DoRelocationFixup(objsec:TObjSection);virtual;abstract;
        function MemAlign(exesec: TExeSection): longword;
        function DataAlign(exesec: TExeSection): longword;
        procedure ReplaceExeSectionList(newlist: TFPList);
      public
        CurrDataPos  : aword;
        MaxMemPos    : qword;
        IsSharedLibrary : boolean;
        ExecStack    : boolean;
        constructor create;virtual;
        destructor  destroy;override;
        function  FindExeSection(const aname:string):TExeSection;
        procedure AddObjData(ObjData:TObjData);
        procedure Load_Start;virtual;
        procedure Load_EntryName(const aname:string);virtual;
        procedure Load_Symbol(const aname:string);virtual;
        procedure Load_ProvideSymbol(const aname:string);virtual;
        procedure Load_IsSharedLibrary;
        procedure Load_ImageBase(const avalue:string);
        procedure Load_DynamicObject(ObjData:TObjData;asneeded:boolean);virtual;
        procedure Order_Start;virtual;
        procedure Order_End;virtual;
        procedure Order_ExeSection(const aname:string);virtual;
        procedure Order_Align(const avalue:string);virtual;
        procedure Order_Zeros(const avalue:string);virtual;
        procedure Order_Values(bytesize : aword; const avalue:string);virtual;
        procedure Order_Symbol(const aname:string);virtual;
        procedure Order_ProvideSymbol(const aname:string);virtual;
        procedure Order_EndExeSection;virtual;
        procedure Order_ObjSection(const aname:string);virtual;
        procedure MemPos_Start;virtual;
        procedure MemPos_Header;virtual;
        procedure MemPos_ExeSection(exesec:TExeSection);
        procedure MemPos_ExeSection(const aname:string);virtual;
        procedure MemPos_EndExeSection;virtual;
        procedure DataPos_Start;virtual;
        procedure DataPos_Header;virtual;
        procedure DataPos_ExeSection(exesec:TExeSection);
        procedure DataPos_ExeSection(const aname:string);virtual;
        procedure DataPos_EndExeSection;virtual;
        procedure DataPos_Symbols;virtual;
        procedure BuildVTableTree(VTInheritList,VTEntryList:TFPObjectList);
        procedure PackUnresolvedExeSymbols(const s:string);
        procedure ResolveSymbols(StaticLibraryList:TFPObjectList);
        procedure PrintMemoryMap;
        procedure FixupSymbols;
        procedure FixupRelocations;virtual;
        procedure RemoveUnusedExeSymbols;
        procedure MergeStabs;
        procedure MarkEmptySections;
        procedure RemoveUnreferencedSections;
        procedure RemoveDisabledSections;
        procedure RemoveDebugInfo;
        procedure MarkTargetSpecificSections(WorkList:TFPObjectList);virtual;
        procedure AfterUnusedSectionRemoval;virtual;
        procedure GenerateLibraryImports(ImportLibraryList:TFPHashObjectList);virtual;
        procedure GenerateDebugLink(const dbgname:string;dbgcrc:cardinal);
        function WriteExeFile(const fn:string):boolean;
        procedure ParseScript (linkscript:TCmdStrList); virtual;
        property Writer:TObjectWriter read FWriter;
        property ExeSectionList:TFPHashObjectList read FExeSectionList;
        property ObjDataList:TFPObjectList read FObjDataList;
        property ExeSymbolList:TFPHashObjectList read FExeSymbolList;
        property UnresolvedExeSymbols:TFPObjectList read FUnresolvedExeSymbols;
        property ExternalObjSymbols:TFPObjectList read FExternalObjSymbols;
        property CommonObjSymbols:TFPObjectList read FCommonObjSymbols;
        property IndirectObjSymbols:TFPObjectList read FIndirectObjSymbols;
        property ExeVTableList:TFPObjectList read FExeVTableList;
        property EntryName:string read FEntryName write FEntryName;
        property ImageBase:qword read FImageBase write FImageBase;
        property CurrExeSec:TExeSection read FCurrExeSec;
        property ExeWriteMode:TExeWriteMode read FExeWriteMode write FExeWriteMode;
        property CurrMemPos:qword read FCurrMemPos write SetCurrMemPos;
      end;
      TExeOutputClass=class of TExeOutput;

    const
      SectionDataMaxGrow = 4096;

    var
      exeoutput : TExeOutput;

    function align_aword(v:aword;a:longword):aword;
    function align_qword(v:qword;a:longword):qword;
    function align_objsecofs(v:TObjSectionOfs;a:longword):TObjSectionOfs;
    procedure MaybeSwapStab(var v:TObjStabEntry);

implementation

    uses
      SysUtils,
      globals,verbose,
{$ifdef OMFOBJSUPPORT}
      omfbase,
{$endif OMFOBJSUPPORT}
      ogmap;

{$ifdef MEMDEBUG}
    var
      memobjsymbols,
      memobjsections : TMemDebug;
{$endif MEMDEBUG}

{*****************************************************************************
                                 Helpers
*****************************************************************************}

    function align_aword(v:aword;a:longword):aword;
      begin
        if a>0 then
          a:=a-1;
        result:=(v+a) and aword(not aword(a));
      end;


    function align_qword(v:qword;a:longword):qword;
      begin
        if a>0 then
          a:=a-1;
        result:=(v+a) and qword(not qword(a));
      end;


    function align_objsecofs(v:TObjSectionOfs;a:longword):TObjSectionOfs;
      begin
        if a>0 then
          a:=a-1;
        result:=(v+a) and TObjSectionOfs(not TObjSectionOfs(a));
      end;


    procedure MaybeSwapStab(var v:TObjStabEntry);
      begin
        if source_info.endian<>target_info.endian then
          begin
            v.strpos:=SwapEndian(v.strpos);
            v.nvalue:=SwapEndian(v.nvalue);
            v.ndesc:=SwapEndian(v.ndesc);
          end;
      end;

{*****************************************************************************
                                 TObjSymbol
*****************************************************************************}

    constructor TObjSymbol.create(AList:TFPHashObjectList;const AName:string);
      begin
        inherited create(AList,AName);
        bind:=AB_EXTERNAL;
        typ:=AT_NONE;
        symidx:=-1;
        size:=0;
        offset:=0;
        objsection:=nil;
      end;


    function TObjSymbol.ToString: ansistring;
      var
        objsectionstr: ansistring;
      begin
        if Assigned(objsection) then
          objsectionstr:=objsection.ToString
        else
          objsectionstr:='nil';
        WriteStr(Result,'(Name:',Name,';bind:',bind,';typ:',typ,';pass:',pass,
          ';refs:',refs,';symidx:',symidx,';objsection:',objsectionstr,';offset:',
          offset,';size:',size,')');
      end;


    function TObjSymbol.address:qword;
      begin
        if assigned(objsection) then
          result:=offset+objsection.mempos
        else
          result:=0;
      end;


    procedure TObjSymbol.SetAddress(apass:byte;aobjsec:TObjSection;abind:TAsmsymbind;atyp:Tasmsymtype);
      begin
        if not(abind in [AB_GLOBAL,AB_PRIVATE_EXTERN,AB_LOCAL,AB_COMMON,AB_IMPORT,AB_WEAK]) then
          internalerror(200603016);
        if not assigned(aobjsec) then
          internalerror(200603017);
        if (bind in [AB_EXTERNAL,AB_LAZY]) or
          { Put all COMMON to GLOBAL in step 3 of
            TExeOutput.ResolveSymbols }
           ((abind=AB_GLOBAL) and (bind=AB_COMMON)) then
          begin
            { Do not change the AB_TYPE of common symbols yet }
            { This will be done in FixupSymbols }
            if (pass<>0) or (bind<>AB_COMMON) then
              bind:=abind;
            typ:=atyp;
          end
        else
          begin
            if pass=apass then
              begin
                Message1(asmw_e_duplicate_label,name);
                exit;
              end;
          end;
        pass:=apass;
        { Code can never grow after a pass }
        if assigned(objsection) and
           (objsection=aobjsec) and
           (aobjsec.size>offset) then
          internalerror(200603014);
        objsection:=aobjsec;
        offset:=aobjsec.size;
      end;


    function TObjSymbol.ObjData: TObjData;
      begin
        result:=(OwnerList as TObjSymbolList).Owner;
      end;


    function TObjSymbol.AddressStr(AImageBase: qword): string;
      begin
        Result:='0x'+HexStr(address+Aimagebase,sizeof(pint)*2);
      end;

{****************************************************************************
                              TObjRelocation
****************************************************************************}

    constructor TObjRelocation.CreateSymbol(ADataOffset:TObjSectionOfs;s:TObjSymbol;Atyp:TObjRelocationType);
      begin
        if not assigned(s) then
          internalerror(200603034);
        DataOffset:=ADataOffset;
        Symbol:=s;
        OrgSize:=0;
        Group:=nil;
        ObjSection:=nil;
        ftype:=ord(Atyp);
      end;


    constructor TObjRelocation.CreateSection(ADataOffset:TObjSectionOfs;aobjsec:TObjSection;Atyp:TObjRelocationType);
      begin
        if not assigned(aobjsec) then
          internalerror(200603036);
        DataOffset:=ADataOffset;
        Symbol:=nil;
        OrgSize:=0;
        Group:=nil;
        ObjSection:=aobjsec;
        ftype:=ord(Atyp);
      end;


    constructor TObjRelocation.CreateGroup(ADataOffset:TObjSectionOfs;grp:TObjSectionGroup;Atyp:TObjRelocationType);
      begin
        if not assigned(grp) then
          internalerror(2015111201);
        DataOffset:=ADataOffset;
        Symbol:=nil;
        ObjSection:=nil;
        OrgSize:=0;
        Group:=grp;
        ftype:=ord(Atyp);
      end;


    constructor TObjRelocation.CreateRaw(ADataOffset:TObjSectionOfs;s:TObjSymbol;ARawType:byte);
      begin
        { nil symbol is allowed here }
        DataOffset:=ADataOffset;
        Symbol:=s;
        ObjSection:=nil;
        Group:=nil;
        orgsize:=0;
        ftype:=ARawType;
        flags:=rf_raw;
      end;


    function TObjRelocation.GetType:TObjRelocationType;
      begin
        if (flags and rf_raw)=0 then
          result:=TObjRelocationType(ftype)
        else
          result:=RELOC_RAW;
      end;


    procedure TObjRelocation.SetType(v:TObjRelocationType);
      begin
        ftype:=ord(v);
        flags:=flags and (not rf_raw);
      end;


    function TObjRelocation.TargetName:TSymStr;
      begin
        if assigned(symbol) then
          if symbol.typ=AT_SECTION then
            result:=symbol.objsection.name
          else
            result:=symbol.Name
        else
          result:=objsection.Name;
      end;


    function TObjRelocation.ToString: ansistring;
      var
        typstr,
        symbolstr,
        objsectionstr,
        groupstr: ansistring;
      begin
        Str(typ,typstr);
        if Assigned(symbol) then
          symbolstr:=symbol.ToString
        else
          symbolstr:='nil';
        if Assigned(objsection) then
          objsectionstr:=objsection.ToString
        else
          objsectionstr:='nil';
        if Assigned(group) then
          groupstr:=group.ToString
        else
          groupstr:='nil';
        Result:='(typ:'+typstr+';DataOffset:'+tostr(DataOffset)+
          ';orgsize:'+tostr(orgsize)+';symbol:'+symbolstr+
          ';objsection:'+objsectionstr+';group:'+groupstr+
          ';ftype:'+tostr(ftype)+';size:'+tostr(size)+
          ';flags:'+tostr(flags)+')';
      end;

{****************************************************************************
                              TObjSection
****************************************************************************}

    constructor TObjSection.create(AList:TFPHashObjectList;const Aname:string;Aalign:longint;Aoptions:TObjSectionOptions);
      begin
        inherited Create(AList,Aname);
        { Data }
        Size:=0;
        Datapos:=0;
        mempos:=0;
        FData:=Nil;
{$ifdef i8086}
        FSizeLimit:=high(word);
{$else i8086}
        FSizeLimit:=high(TObjSectionOfs);
{$endif i8086}
        { Setting the secoptions allocates Data if needed }
        secoptions:=Aoptions;
        if (Aalign and (Aalign-1))<>0 then
          internalerror(2022010401); { alignment is not a power of two }
        secalign:=Aalign;
        secsymidx:=0;
        { relocation }
        ObjRelocations:=TFPObjectList.Create(true);
        VTRefList:=TFPObjectList.Create(false);
      end;


    destructor TObjSection.destroy;
      begin
        if assigned(Data) then
          Data.Free;
        stringdispose(FCachedFullName);
        ObjRelocations.Free;
        VTRefList.Free;
        inherited destroy;
      end;


    function TObjSection.ToString: ansistring;
      begin
        System.WriteStr(Result,'(Name:',Name,';index',index,';SecSymIdx:',SecSymIdx,
          ';SecAlign:',SecAlign,';Size:',Size,';DataPos:',DataPos,';MemPos:',
          MemPos,';DataAlignBytes:',DataAlignBytes,';Used:',Used,')');
      end;


    procedure TObjSection.SetSecOptions(Aoptions:TObjSectionOptions);
      begin
        FSecOptions:=FSecOptions+AOptions;
        if (oso_Data in secoptions) and
           not assigned(FData) then
          FData:=TDynamicArray.Create(SectionDataMaxGrow);
      end;


    procedure TObjSection.SectionTooLargeError;
      begin
        if oso_executable in SecOptions then
          Message(asmw_f_code_segment_too_large)
        else
          Message(asmw_f_data_segment_too_large);
      end;


    function TObjSection.GetAltName: string;
      begin
        result:='';
      end;


    function TObjSection.write(const d;l:TObjSectionOfs):TObjSectionOfs;
      begin
        result:=size;
        if assigned(Data) then
          begin
            if Size<>Data.size then
              internalerror(200602281);
{$ifndef cpu64bitaddr}
            if (qword(size)+l)>SizeLimit then
              SectionTooLargeError;
{$endif}
            Data.write(d,l);
            inc(Size,l);
          end
        else
          internalerror(200602289);
      end;


    procedure TObjSection.writeInt8(v: int8);
      begin
        write(v,1);
      end;


    procedure TObjSection.writeInt16LE(v: int16);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        write(v,2);
      end;


    procedure TObjSection.writeInt16BE(v: int16);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        write(v,2);
      end;


    procedure TObjSection.writeInt32LE(v: int32);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        write(v,4);
      end;


    procedure TObjSection.writeInt32BE(v: int32);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        write(v,4);
      end;


    procedure TObjSection.writeInt64LE(v: int64);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        write(v,8);
      end;


    procedure TObjSection.writeInt64BE(v: int64);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        write(v,8);
      end;


    procedure TObjSection.writeUInt8(v: uint8);
      begin
        write(v,1);
      end;


    procedure TObjSection.writeUInt16LE(v: uint16);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        write(v,2);
      end;


    procedure TObjSection.writeUInt16BE(v: uint16);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        write(v,2);
      end;


    procedure TObjSection.writeUInt32LE(v: uint32);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        write(v,4);
      end;


    procedure TObjSection.writeUInt32BE(v: uint32);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        write(v,4);
      end;


    procedure TObjSection.writeUInt64LE(v: uint64);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        write(v,8);
      end;


    procedure TObjSection.writeUInt64BE(v: uint64);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        write(v,8);
      end;


    function TObjSection.writestr(const s:string):TObjSectionOfs;
      var
        b: byte;
      begin
        result:=Write(s[1],length(s));
        b:=0;
        Write(b,1);
      end;


    function TObjSection.WriteBytes(const s:string):TObjSectionOfs;
      begin
        result:=Write(s[1],length(s));
      end;


    function TObjSection.WriteZeros(l:longword):TObjSectionOfs;
      var
        empty : array[0..1023] of byte;
      begin
        result:=Size;
        if l>sizeof(empty) then
          begin
            fillchar(empty,sizeof(empty),0);
            while l>sizeof(empty) do
              begin
                Write(empty,sizeof(empty));
                Dec(l,sizeof(empty));
              end;
            if l>0 then
              Write(empty,l);
          end
        else if l>0 then
          begin
            fillchar(empty,l,0);
            Write(empty,l);
          end;
      end;


    { Writes relocation to (section+offset) without need to have a symbol at that location.
      Not an abstract method because not every backend needs this functionality. }
    procedure TObjSection.writeReloc_internal(aTarget:TObjSection;offset:aword;len:byte;reltype:TObjRelocationType);
      begin
        InternalError(2012081501);
      end;


    procedure TObjSection.setDatapos(var dpos:TObjSectionOfs);
      begin
        if oso_Data in secoptions then
          begin
            { get aligned Datapos }
            Datapos:=align_aword(dpos,secalign);
            Dataalignbytes:=Datapos-dpos;
            { return updated Datapos }
            dpos:=Datapos+size;
          end
        else
          Datapos:=dpos;
      end;


    function TObjSection.setmempos(mpos:qword):qword;
      begin
        mempos:=align_qword(mpos,secalign);
        { return updated mempos }
        result:=mempos+size;
      end;


    procedure TObjSection.alloc(l:TObjSectionOfs);
      begin
{$ifndef cpu64bitaddr}
        if (qword(size)+l)>SizeLimit then
          SectionTooLargeError;
{$endif}
        if oso_sparse_data in SecOptions then
          WriteZeros(l)
        else
          inc(size,l);
      end;


    procedure TObjSection.addsymReloc(ofs:TObjSectionOfs;p:TObjSymbol;Reloctype:TObjRelocationType);
      begin
        ObjRelocations.Add(TObjRelocation.CreateSymbol(ofs,p,reloctype));
      end;


    procedure TObjSection.addsectionReloc(ofs:TObjSectionOfs;aobjsec:TObjSection;Reloctype:TObjRelocationType);
      begin
        ObjRelocations.Add(TObjRelocation.CreateSection(ofs,aobjsec,reloctype));
      end;


    procedure TObjSection.addrawReloc(ofs:TObjSectionOfs;p:TObjSymbol;RawReloctype:byte);
      begin
        ObjRelocations.Add(TObjRelocation.CreateRaw(ofs,p,RawReloctype));
      end;


    procedure TObjSection.ReleaseData;
      begin
        if assigned(FData) then
          begin
            FData.free;
            FData:=nil;
          end;
        ObjRelocations.free;
        ObjRelocations:=nil;
        if assigned(FCachedFullName) then
          begin
            stringdispose(FCachedFullName);
            FCachedFullName:=nil;
          end;
      end;


    function  TObjSection.FullName:string;
      var
        s: string;
      begin
        if not assigned(FCachedFullName) then
          begin
            s:=GetAltName;
            if s<>'' then
              s:=Name+s
            else
              s:=Name;
            if assigned(ObjData) then
              FCachedFullName:=stringdup(ObjData.Name+'('+s+')')
            else
              FCachedFullName:=stringdup(s);
          end;
        result:=FCachedFullName^;
      end;


    function  TObjSection.MemPosStr(AImageBase: qword): string;
      begin
        result:='0x'+HexStr(mempos+AImageBase,sizeof(pint)*2);
      end;


{****************************************************************************
                                TObjData
****************************************************************************}

    constructor TObjData.create(const n:string);
      begin
        inherited create;
        FName:=ExtractFileName(n);
        FObjSectionList:=TFPHashObjectList.Create(true);
        FStabsObjSec:=nil;
        FStabStrObjSec:=nil;
        { symbols }
        FCObjSymbol:=TObjSymbol;
        FObjSymbolList:=TObjSymbolList.Create(true);
        FObjSymbolList.Owner:=Self;
        FCachedAsmSymbolList:=TFPObjectList.Create(false);
        { section class type for creating of new sections }
        FCObjSection:=TObjSection;
        FCObjSectionGroup:=TObjSectionGroup;
{$ifdef ARM}
        ThumbFunc:=false;
{$endif ARM}
      end;


    destructor TObjData.destroy;
      begin
        { Symbols }
{$ifdef MEMDEBUG}
        MemObjSymbols.Start;
{$endif}
        ResetCachedAsmSymbols;
        FCachedAsmSymbolList.free;
        FObjSymbolList.free;
{$ifdef MEMDEBUG}
        MemObjSymbols.Stop;
{$endif}
        GroupsList.free;

        { Sections }
{$ifdef MEMDEBUG}
        MemObjSections.Start;
{$endif}
        FObjSectionList.free;
{$ifdef MEMDEBUG}
        MemObjSections.Stop;
{$endif}
        inherited destroy;
      end;


    class function TObjData.sectiontype2options(atype:TAsmSectiontype):TObjSectionOptions;
      const
        secoptions : array[TAsmSectiontype] of TObjSectionOptions = ([],
          {user} [oso_Data,oso_load,oso_write],
          {code} [oso_Data,oso_load,oso_executable],
          {Data} [oso_Data,oso_load,oso_write],
          { Readonly data with relocations must be initially writable for some targets.
            Moreover, e.g. for ELF it depends on whether the executable is linked statically or
            dynamically. Here we declare it writable, target-specific descendants must provide
            further handling. }
          {roData} [oso_Data,oso_load,oso_write],
          {roData_norel} [oso_Data,oso_load],
          {bss} [oso_load,oso_write],
          {threadvar} [oso_load,oso_write,oso_threadvar],
          {pdata} [oso_data,oso_load],
          {stub} [oso_Data,oso_load,oso_executable],
          {data_nonlazy}  [oso_Data,oso_load,oso_write],
          {data_lazy} [oso_Data,oso_load,oso_write],
          {init_func} [oso_Data,oso_load],
          {term_func} [oso_Data,oso_load],
          {stab} [oso_Data,oso_debug],
          {stabstr} [oso_Data,oso_strings,oso_debug],
          {iData2} [oso_Data,oso_load,oso_write],
          {iData4} [oso_Data,oso_load,oso_write],
          {iData5} [oso_Data,oso_load,oso_write],
          {iData6} [oso_Data,oso_load,oso_write],
          {iData7} [oso_Data,oso_load,oso_write],
          {eData} [oso_Data,oso_load],
          {eh_frame} [oso_Data,oso_load],
          {debug_frame} [oso_Data,oso_debug],
          {debug_info} [oso_Data,oso_debug],
          {debug_line} [oso_Data,oso_debug],
          {debug_abbrev} [oso_Data,oso_debug],
          {debug_aranges} [oso_Data,oso_debug],
          {debug_ranges} [oso_Data,oso_debug],
          {debug_loc} [oso_Data,oso_debug],
          {debug_loclists} [oso_Data,oso_debug],
          {fpc} [oso_Data,oso_load,oso_write],
          {toc} [oso_Data,oso_load],
          {init} [oso_Data,oso_load,oso_executable],
          {fini} [oso_Data,oso_load,oso_executable],
          {objc_class} [oso_data,oso_load],
          {objc_meta_class} [oso_data,oso_load],
          {objc_cat_cls_meth} [oso_data,oso_load],
          {objc_cat_inst_meth} [oso_data,oso_load],
          {objc_protocol} [oso_data,oso_load],
          {objc_string_object} [oso_data,oso_load],
          {objc_cls_meth} [oso_data,oso_load],
          {objc_inst_meth} [oso_data,oso_load],
          {objc_cls_refs} [oso_data,oso_load],
          {objc_message_refs} [oso_data,oso_load],
          {objc_symbols} [oso_data,oso_load],
          {objc_category} [oso_data,oso_load],
          {objc_class_vars} [oso_data,oso_load],
          {objc_instance_vars} [oso_data,oso_load],
          {objc_module_info} [oso_data,oso_load],
          {objc_class_names} [oso_data,oso_load],
          {objc_meth_var_types} [oso_data,oso_load],
          {objc_meth_var_names} [oso_data,oso_load],
          {objc_selector_strs} [oso_data,oso_load],
          {objc_protocol_ext} [oso_data,oso_load],
          {objc_class_ext} [oso_data,oso_load],
          {objc_property} [oso_data,oso_load],
          {objc_image_info} [oso_data,oso_load],
          {objc_cstring_object} [oso_data,oso_load],
          {objc_sel_fixup} [oso_data,oso_load],
          {sec_objc_data} [oso_data,oso_load],
          {sec_objc_const} [oso_data,oso_load],
          {sec_objc_sup_refs} [oso_data,oso_load],
          {sec_data_coalesced} [oso_data,oso_load],
          {sec_objc_classlist} [oso_data,oso_load],
          {sec_objc_nlclasslist} [oso_data,oso_load],
          {sec_objc_catlist} [oso_data,oso_load],
          {sec_objc_nlcatlist} [oso_data,oso_load],
          {sec_objc_protolist'} [oso_data,oso_load],
          {stack} [oso_load,oso_write],
          {heap} [oso_load,oso_write],
          {gcc_except_table} [oso_data,oso_load],
          {arm_attribute} [oso_data],
          {note} [oso_Data,oso_note]
        );
      begin
        if target_asm.id in asms_int_coff then
          begin
            if (aType in [sec_rodata,sec_rodata_norel]) then
              begin
                if (target_info.system in systems_all_windows) then
                  aType:=sec_rodata_norel
                else
                  aType:=sec_data;
              end;
          end;
        result:=secoptions[atype];
        if (target_info.system in systems_wasm) and (atype=sec_bss) then
          Result:=Result+[oso_data,oso_sparse_data];
{$ifdef OMFOBJSUPPORT}
        { in the huge memory model, BSS data is actually written in the regular
          FAR_DATA segment of the module }
        if omf_segclass(atype)='FAR_DATA' then
          Result:=Result+[oso_data,oso_sparse_data];
{$endif OMFOBJSUPPORT}
      end;


    function TObjData.sectiontype2align(atype:TAsmSectiontype):longint;
      begin
        case atype of
          sec_stabstr,sec_debug_info,sec_debug_line,sec_debug_abbrev,sec_debug_aranges,sec_debug_ranges,
          sec_arm_attribute:
            result:=1;
          sec_code,
          sec_bss,
          sec_data:
            result:=16;
          { For idata (at least idata2) it must be 4 bytes, because
            an entry is always (also in win64) 20 bytes and aligning
            on 8 bytes will insert 4 bytes between the entries resulting
            in a corrupt idata section.
            Same story with .pdata, it has 4-byte elements which should
            be packed without gaps. }
          sec_idata2,sec_idata4,sec_idata5,sec_idata6,sec_idata7,sec_pdata:
            result:=4;
          else
            result:=sizeof(pint);
        end;
      end;


    class procedure TObjData.sectiontype2progbitsandflags(atype:TAsmSectiontype;out progbits:TSectionProgbits;out flags:TSectionFlags);
      var
        options : TObjSectionOptions;
      begin
        { this is essentially the inverse of the createsection overload that takes
          both progbits and flags as parameters }
        options:=sectiontype2options(atype);
        flags:=[];
        progbits:=SPB_None;
        if oso_load in options then
          include(flags,SF_A);
        if oso_write in options then
          include(flags,SF_W);
        if oso_executable in options then
          include(flags,SF_X);
        if not (oso_data in options) then
          progbits:=SPB_NOBITS
        else if oso_note in options then
          progbits:=SPB_NOTE
        else if oso_arm_attributes in options then
          progbits:=SPB_ARM_ATTRIBUTES;
      end;


    function TObjData.createsection(atype:TAsmSectionType;const aname:string;aorder:TAsmSectionOrder):TObjSection;
      begin
        result:=createsection(sectionname(atype,aname,aorder),sectiontype2align(atype),sectiontype2options(atype));
      end;


    function TObjData.createsection(atype: TAsmSectionType; secflags: TSectionFlags; aprogbits: TSectionProgbits; const aname: string; aorder: TAsmSectionOrder): TObjSection;
      var
        flags : TObjSectionOptions;
      begin
        flags:=[oso_data];
        if SF_A in secflags then
          Include(flags,oso_load);
        if SF_W in secflags then
          Include(flags,oso_write);
        if SF_X in secflags then
          Include(flags,oso_executable);
        if aprogbits=SPB_NOBITS then
          Exclude(flags,oso_data);
        if aprogbits=SPB_NOTE then
          Include(flags,oso_note);
        if aprogbits=SPB_ARM_ATTRIBUTES then
          Include(flags,oso_arm_attributes);
        result:=createsection(sectionname(atype,aname,aorder),sectiontype2align(atype),flags);
      end;


    function TObjData.createsection(const aname:string;aalign:longint;aoptions:TObjSectionOptions;DiscardDuplicate:boolean):TObjSection;
      begin
        if DiscardDuplicate then
          result:=TObjSection(FObjSectionList.Find(aname))
        else
          result:=nil;
        if not assigned(result) then
          begin
            result:=CObjSection.create(FObjSectionList,aname,aalign,aoptions);
            result.ObjData:=self;
          end;
        FCurrObjSec:=result;
      end;


    function TObjData.CreateSectionGroup(const aname:string):TObjSectionGroup;
      begin
        if FGroupsList=nil then
          FGroupsList:=TFPHashObjectList.Create(true);
        result:=CObjSectionGroup.Create(FGroupsList,aname);
      end;


    procedure TObjData.CreateDebugSections;
      begin
      end;


    function TObjData.Findsection(const aname:string):TObjSection;
      begin
        result:=TObjSection(FObjSectionList.Find(aname));
      end;


    procedure TObjData.setsection(asec:TObjSection);
      begin
        if asec.ObjData<>self then
          internalerror(200403041);
        FCurrObjSec:=asec;
      end;


    function TObjData.createsymbol(const aname:string):TObjSymbol;
      begin
        result:=TObjSymbol(FObjSymbolList.Find(aname));
        if not assigned(result) then
          result:=CObjSymbol.Create(FObjSymbolList,aname);

{$ifdef ARM}
        result.ThumbFunc:=ThumbFunc;
        ThumbFunc:=false;
{$endif ARM}
      end;


    function TObjData.symboldefine(asmsym:TAsmSymbol):TObjSymbol;
      begin
        if assigned(asmsym) then
          begin
            if asmsym.typ = AT_NONE then
              InternalError(2018062800);

            if not assigned(asmsym.cachedObjSymbol) then
              begin
                result:=symboldefine(asmsym.name,asmsym.bind,asmsym.typ);
                asmsym.cachedObjSymbol:=result;
                FCachedAsmSymbolList.add(asmsym);
              end
            else
              begin
                result:=TObjSymbol(asmsym.cachedObjSymbol);
                result.SetAddress(CurrPass,CurrObjSec,asmsym.bind,asmsym.typ);
              end;
          end
        else
          result:=nil;
      end;


    function TObjData.symboldefine(const aname:string;abind:TAsmsymbind;atyp:Tasmsymtype):TObjSymbol;
      begin
        if not assigned(CurrObjSec) then
          internalerror(2006030504);
        result:=CreateSymbol(aname);
        result.SetAddress(CurrPass,CurrObjSec,abind,atyp);
      end;


    function TObjData.symbolref(asmsym:TAsmSymbol):TObjSymbol;
      var
        s:string;
      begin
        if assigned(asmsym) then
          begin
            if not assigned(asmsym.cachedObjSymbol) then
              begin
                s:=asmsym.name;
                result:=TObjSymbol(FObjSymbolList.Find(s));
                if result=nil then
                  begin
                    result:=CObjSymbol.Create(FObjSymbolList,s);
                    if asmsym.bind=AB_WEAK_EXTERNAL then
                      result.bind:=AB_WEAK_EXTERNAL;
                  end;
                asmsym.cachedObjSymbol:=result;
                FCachedAsmSymbolList.add(asmsym);
              end
            else
              result:=TObjSymbol(asmsym.cachedObjSymbol);
            { The weak bit could have been removed from asmsym. }
            if (asmsym.bind=AB_EXTERNAL) and (result.bind=AB_WEAK_EXTERNAL) then
              result.bind:=AB_EXTERNAL;
            { the TLS type needs to be inherited }
            if asmsym.typ=AT_TLS then
              result.typ:=AT_TLS;
          end
        else
          result:=nil;
      end;


    function TObjData.symbolref(const aname:string):TObjSymbol;
      begin
        if not assigned(CurrObjSec) then
          internalerror(200603052);
        result:=CreateSymbol(aname);
      end;


    procedure TObjData.symbolpairdefine(akind: TSymbolPairKind; const asym, avalue: string);
      begin
      end;


    procedure TObjData.ResetCachedAsmSymbols;
      var
        i  : longint;
      begin
        for i:=0 to FCachedAsmSymbolList.Count-1 do
          tasmsymbol(FCachedAsmSymbolList[i]).cachedObjSymbol:=nil;
        FCachedAsmSymbolList.Clear;
      end;


    procedure TObjData.writebytes(const Data;len:TObjSectionOfs);
      begin
        if not assigned(CurrObjSec) then
          internalerror(200402251);
        CurrObjSec.write(Data,len);
      end;

    procedure TObjData.writebytes(const Data: TByteDynArray; len: TObjSectionOfs);
    begin
      if len>0 then
        WriteBytes(Data[0],len);
    end;

    procedure TObjData.writebytes(const Data: TAnsiCharDynArray; len: TObjSectionOfs);
    begin
      if len>0 then
        WriteBytes(Data[0],len);
    end;


    procedure TObjData.writeInt8(v: int8);
      begin
        writebytes(v,1);
      end;


    procedure TObjData.writeInt16LE(v: int16);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        writebytes(v,2);
      end;


    procedure TObjData.writeInt16BE(v: int16);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        writebytes(v,2);
      end;


    procedure TObjData.writeInt32LE(v: int32);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        writebytes(v,4);
      end;


    procedure TObjData.writeInt32BE(v: int32);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        writebytes(v,4);
      end;


    procedure TObjData.writeInt64LE(v: int64);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        writebytes(v,8);
      end;


    procedure TObjData.writeInt64BE(v: int64);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        writebytes(v,8);
      end;


    procedure TObjData.writeUInt8(v: uint8);
      begin
        writebytes(v,1);
      end;


    procedure TObjData.writeUInt16LE(v: uint16);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        writebytes(v,2);
      end;


    procedure TObjData.writeUInt16BE(v: uint16);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        writebytes(v,2);
      end;


    procedure TObjData.writeUInt32LE(v: uint32);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        writebytes(v,4);
      end;


    procedure TObjData.writeUInt32BE(v: uint32);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        writebytes(v,4);
      end;


    procedure TObjData.writeUInt64LE(v: uint64);
      begin
{$ifdef FPC_BIG_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_BIG_ENDIAN}
        writebytes(v,8);
      end;


    procedure TObjData.writeUInt64BE(v: uint64);
      begin
{$ifdef FPC_LITTLE_ENDIAN}
        v:=SwapEndian(v);
{$endif FPC_LITTLE_ENDIAN}
        writebytes(v,8);
      end;


    procedure TObjData.alloc(len:TObjSectionOfs);
      begin
        if not assigned(CurrObjSec) then
          internalerror(200402252);
        CurrObjSec.alloc(len);
      end;


    procedure TObjData.allocalign(len:longint);
      begin
        if not assigned(CurrObjSec) then
          internalerror(200402253);
        CurrObjSec.alloc(align_objsecofs(CurrObjSec.size,len)-CurrObjSec.size);
      end;


    procedure TObjData.section_afteralloc(p:TObject;arg:pointer);
      begin
        with TObjSection(p) do
          alloc(align_objsecofs(size,secalign)-size);
      end;


    procedure TObjData.section_afterwrite(p:TObject;arg:pointer);
      begin
        with TObjSection(p) do
          begin
            if assigned(Data) then
              writezeros(align_objsecofs(size,secalign)-size);
          end;
      end;


    procedure TObjData.section_reset(p:TObject;arg:pointer);
      begin
        with TObjSection(p) do
          begin
            Size:=0;
            Datapos:=0;
            mempos:=0;
            if assigned(Data) then
              Data.reset;
          end;
      end;


    procedure TObjData.beforealloc;
      begin
        FCPUType:=current_settings.cputype;
        { create stabs sections if debugging }
        if assigned(StabsSec) then
          begin
            StabsSec.Alloc(sizeof(TObjStabEntry));
            StabStrSec.Alloc(1);
          end;
      end;


    procedure TObjData.beforewrite;
      begin
        FCPUType:=current_settings.cputype;
        { create stabs sections if debugging }
        if assigned(StabsSec) then
         begin
           { Create dummy HdrSym stab, it will be overwritten in AfterWrite }
           StabsSec.WriteZeros(sizeof(TObjStabEntry));
           { start of stabstr }
           StabStrSec.writeZeros(1);
         end;
      end;


    procedure TObjData.afteralloc;
      begin
        FObjSectionList.ForEachCall(@section_afteralloc,nil);
      end;


    procedure TObjData.afterwrite;
      var
        hstab : TObjStabEntry;
      begin
        FObjSectionList.ForEachCall(@section_afterwrite,nil);
        { For the stab section we need an HdrSym which can now be
          calculated more easily }
        if assigned(StabsSec) then
          begin
            { end of stabstr }
            StabStrSec.writeZeros(1);
            { header stab }
            hstab.strpos:=1;
            hstab.ntype:=0;
            hstab.nother:=0;
{$push}{$R-}
            { for jwawindows.pas, this causes an range check error, it contains too much stab symbols }
            hstab.ndesc:=(StabsSec.Size div sizeof(TObjStabEntry))-1;
{$pop}
            hstab.nvalue:=StabStrSec.Size;
            MaybeSwapStab(hstab);
            StabsSec.Data.seek(0);
            StabsSec.Data.write(hstab,sizeof(hstab));
          end;
      end;


    procedure TObjData.resetsections;
      begin
        FObjSectionList.ForEachCall(@section_reset,nil);
      end;


        procedure TObjData.layoutsections(var datapos: TObjSectionOfs);
      var
        i: longint;
      begin
        for i:=0 to FObjSectionList.Count-1 do
          TObjSection(FObjSectionList[i]).setDatapos(DataPos);
      end;


{****************************************************************************
                                TObjOutput
****************************************************************************}

    constructor TObjOutput.create(AWriter:TObjectWriter);
      begin
        FWriter:=AWriter;
        CObjData:=TObjData;
      end;


    destructor TObjOutput.destroy;
      begin
        inherited destroy;
      end;


    function TObjOutput.newObjData(const n:string):TObjData;
      begin
        result:=CObjData.create(n);
        if (cs_use_lineinfo in current_settings.globalswitches) or
           (cs_debuginfo in current_settings.moduleswitches) then
          result.CreateDebugSections;
      end;


    function TObjOutput.startObjectfile(const fn:string):boolean;
      begin
        result:=false;
        { start the writer already, so the .a generation can initialize
          the position of the current objectfile }
        if not FWriter.createfile(fn) then
         Comment(V_Fatal,'Can''t create object '+fn);
        result:=true;
      end;


    function TObjOutput.writeobjectfile(Data:TObjData):boolean;
      begin
        if errorcount=0 then
         result:=writeData(Data)
        else
         result:=true;
        { close the writer }
        FWriter.closefile;
      end;


    procedure TObjOutput.exportsymbol(p:TObjSymbol);
      begin
        { export globals and common symbols, this is needed
          for .a files }
        if p.bind in [AB_GLOBAL,AB_PRIVATE_EXTERN,AB_COMMON] then
         FWriter.writesym(ApplyAsmSymbolRestrictions(p.name));
      end;

    procedure TObjOutput.WriteSectionContent(Data:TObjData);
      var
        i:longint;
        sec:TObjSection;
      begin
        for i:=0 to Data.ObjSectionList.Count-1 do
          begin
            sec:=TObjSection(Data.ObjSectionList[i]);
            if (oso_data in sec.SecOptions) then
              begin
                if sec.Data=nil then
                  internalerror(2004030707);
                FWriter.writezeros(sec.dataalignbytes);
                if sec.Datapos<>FWriter.ObjSize then
                  internalerror(200604031);
                FWriter.writearray(sec.data);
              end;
          end;
      end;

{****************************************************************************
                                 TExeVTable
****************************************************************************}

    constructor TExeVTable.Create(AExeSymbol:TExeSymbol);
      begin
        ExeSymbol:=AExeSymbol;
        if ExeSymbol.State=symstate_undefined then
          internalerror(200604012);
        ChildList:=TFPObjectList.Create(false);
      end;


    destructor TExeVTable.Destroy;
      begin
        ChildList.Free;
        if assigned(EntryArray) then
          Freemem(EntryArray);
      end;


    procedure TExeVTable.CheckIdx(VTableIdx:longint);
      var
        OldEntryCnt : longint;
      begin
        if VTableIdx>=EntryCnt then
          begin
            OldEntryCnt:=EntryCnt;
            EntryCnt:=VTableIdx+1;
            ReAllocMem(EntryArray,EntryCnt*sizeof(TVTableEntry));
            FillChar(EntryArray[OldEntryCnt],(EntryCnt-OldEntryCnt)*sizeof(TVTableEntry),0);
          end;
      end;


    procedure TExeVTable.AddChild(vt:TExeVTable);
      begin
        ChildList.Add(vt);
      end;


    procedure TExeVTable.AddEntry(VTableIdx:Longint);
      var
        i : longint;
        objreloc : TObjRelocation;
        vtblentryoffset : aword;
      begin
        CheckIdx(VTableIdx);
        vtblentryoffset:=ExeSymbol.ObjSymbol.Offset+longword(VTableIdx)*sizeof(pint);
        { Find and disable relocation }
        for i:=0 to ExeSymbol.ObjSymbol.ObjSection.ObjRelocations.Count-1 do
          begin
            objreloc:=TObjRelocation(ExeSymbol.ObjSymbol.ObjSection.ObjRelocations[i]);
            if objreloc.dataoffset=vtblentryoffset then
              begin
                EntryArray[VTableIdx].ObjRelocation:=objreloc;
                EntryArray[VTableIdx].OrgRelocType:=objreloc.ftype;
                EntryArray[VTableIdx].OrgRelocFlags:=objreloc.flags;
                objreloc.typ:=RELOC_ZERO;
                objreloc.flags:=objreloc.flags or rf_nosymbol;
                break;
              end;
          end;
        if not assigned(EntryArray[VTableIdx].ObjRelocation) then
          internalerror(200604011);
      end;


    procedure TExeVTable.SetVTableSize(ASize:longint);
      begin
        if EntryCnt<>0 then
          internalerror(200603313);
        EntryCnt:=ASize div sizeof(pint);
        EntryArray:=AllocMem(EntryCnt*sizeof(TVTableEntry));
      end;


    function TExeVTable.VTableRef(VTableIdx:Longint):TObjRelocation;
      begin
        result:=nil;
        CheckIdx(VTableIdx);
        if EntryArray[VTableIdx].Used then
          exit;
        { Restore relocation if available }
        if assigned(EntryArray[VTableIdx].ObjRelocation) then
          begin
            EntryArray[VTableIdx].ObjRelocation.ftype:=EntryArray[VTableIdx].OrgRelocType;
            EntryArray[VTableIdx].ObjRelocation.flags:=EntryArray[VTableIdx].OrgRelocFlags;
            result:=EntryArray[VTableIdx].ObjRelocation;
          end;
        EntryArray[VTableIdx].Used:=true;
      end;


{****************************************************************************
                                TExeSection
****************************************************************************}

    constructor TExeSection.create(AList:TFPHashObjectList;const AName:string);
      begin
        inherited create(AList,AName);
        Size:=0;
        MemPos:=0;
        DataPos:=0;
        FSecSymIdx:=0;
        FObjSectionList:=TFPObjectList.Create(false);
      end;


    destructor TExeSection.destroy;
      begin
        ObjSectionList.Free;
        inherited destroy;
      end;


    procedure TExeSection.AddObjSection(objsec:TObjSection;ignoreprops:boolean);
      begin
        ObjSectionList.Add(objsec);
        { relate ObjSection to ExeSection, and mark it Used by default }
        objsec.ExeSection:=self;
        objsec.Used:=true;
        if ignoreprops then
          exit;
        if (SecOptions<>[]) then
          begin
            { Only if the section contains (un)initialized data the
              data flag must match. }
            if ((oso_Data in SecOptions)<>(oso_Data in objsec.SecOptions)) then
              Comment(V_Error,'Incompatible section options');
          end
        else
          begin
            { inherit section options }
            SecOptions:=SecOptions+objsec.SecOptions;
          end;
        SecAlign:=max(objsec.SecAlign,SecAlign);
      end;


    function TExeSection.MemPosStr(AImageBase: qword): string;
      begin
        result:='0x'+HexStr(mempos+AImageBase,sizeof(pint)*2);
      end;


{****************************************************************************
                                TStaticLibrary
****************************************************************************}

    constructor TStaticLibrary.create(const AName:TCmdStr;AReader:TObjectReader;AObjInputClass:TObjInputClass);
      begin
        FName:=AName;
        FPayload:=AReader;
        FObjInputClass:=AObjInputClass;
        FKind:=lkArchive;
      end;


    constructor TStaticLibrary.create_object(AObjData:TObjData);
      begin
        FPayload:=AObjData;
        FKind:=lkObject;
      end;


    constructor TStaticLibrary.create_group;
      begin
        FPayload:=TFPObjectList.Create(true);
        FKind:=lkGroup;
      end;


    destructor TStaticLibrary.destroy;
      begin
        FPayload.Free;
        inherited destroy;
      end;


    function TStaticLibrary.GetArReader: TObjectReader;
      begin
        if (FKind<>lkArchive) then
          InternalError(2012071501);
        result:=TObjectReader(FPayload);
      end;


    function TStaticLibrary.GetGroupMembers: TFPObjectList;
      begin
        if (FKind<>lkGroup) then
          InternalError(2012071502);
        result:=TFPObjectList(FPayload);
      end;


    function TStaticLibrary.GetObjData: TObjData;
      begin
        if (FKind<>lkObject) then
          InternalError(2012071503);
        result:=TObjData(FPayload);
      end;

{****************************************************************************
                                TImportLibrary
****************************************************************************}

    constructor TImportLibrary.create(AList:TFPHashObjectList;const AName:string);
      begin
        inherited create(AList,AName);
        FImportSymbolList:=TFPHashObjectList.Create(true);
      end;


    destructor TImportLibrary.destroy;
      begin
        ImportSymbolList.Free;
        inherited destroy;
      end;


{****************************************************************************
                                TImportSymbol
****************************************************************************}

    constructor TImportSymbol.create(AList:TFPHashObjectList;
            const AName,AMangledName:string;AOrdNr:longint;AIsVar:boolean);
      begin
        inherited Create(AList, AName);
        FOrdNr:=AOrdNr;
        FIsVar:=AIsVar;
        FMangledName:=AMangledName;
        { Replace ? and @ in import name, since GNU AS does not allow these characters in symbol names. }
        { This allows to import VC++ mangled names from DLLs. }
        if target_info.system in systems_all_windows then
          begin
            Replace(FMangledName,'?','__q$$');
{$ifdef arm}
            { @ symbol is not allowed in ARM assembler only }
            Replace(FMangledName,'@','__a$$');
{$endif arm}
          end;
      end;


{****************************************************************************
                                TExeOutput
****************************************************************************}

    constructor TExeOutput.create;
      begin
        { init writer }
        FWriter:=TObjectwriter.create;
        FExeWriteMode:=ewm_exefull;
        { object files }
        FObjDataList:=TFPObjectList.Create(true);
        { symbols }
        FExeSymbolList:=TFPHashObjectList.Create(true);
        FUnresolvedExeSymbols:=TFPObjectList.Create(false);
        FExternalObjSymbols:=TFPObjectList.Create(false);
        FCommonObjSymbols:=TFPObjectList.Create(false);
        FProvidedObjSymbols:=TFPObjectList.Create(false);
        FIndirectObjSymbols:=TFPObjectList.Create(false);
        FExeVTableList:=TFPObjectList.Create(false);
        ComdatGroups:=TFPHashList.Create;
        { sections }
        FExeSectionList:=TFPHashObjectList.Create(true);
        FImageBase:=0;
{$ifdef cpu16bitaddr}
        SectionMemAlign:=$10;
        SectionDataAlign:=$10;
{$else cpu16bitaddr}
        SectionMemAlign:=$1000;
        SectionDataAlign:=$200;
{$endif cpu16bitaddr}
        FixedSectionAlign:=True;
        FCExeSection:=TExeSection;
        FCObjData:=TObjData;
        FCObjSymbol:=TObjSymbol;
      end;


    destructor TExeOutput.destroy;
      begin
        FExeSymbolList.free;
        UnresolvedExeSymbols.free;
        ExternalObjSymbols.free;
        FProvidedObjSymbols.free;
        FIndirectObjSymbols.free;
        CommonObjSymbols.free;
        ExeVTableList.free;
        FExeSectionList.free;
        ComdatGroups.free;
        ObjDatalist.free;
        FWriter.free;
        inherited destroy;
      end;


    function TExeOutput.MemAlign(exesec:TExeSection):longword;
      begin
        if FixedSectionAlign then
          result:=SectionMemAlign
        else
          result:=exesec.SecAlign;
      end;


    function TExeOutput.DataAlign(exesec:TExeSection):longword;
      begin
        if FixedSectionAlign then
          result:=SectionDataAlign
        else
          result:=exesec.SecAlign;
      end;


    function TExeOutput.WriteExeFile(const fn:string):boolean;
      begin
        result:=false;
        if FWriter.createfile(fn) then
         begin
           { Only write the .o if there are no errors }
           if errorcount=0 then
             result:=writedata
           else
             result:=true;
           { close the writer }
           FWriter.closefile;
         end
        else
         Comment(V_Fatal,'Can''t create executable '+fn);
      end;


    procedure TExeOutput.ParseScript (linkscript:TCmdStrList);
      begin
      end;


    function  TExeOutput.FindExeSection(const aname:string):TExeSection;
      begin
        result:=TExeSection(ExeSectionList.Find(aname));
      end;


    procedure TExeOutput.AddObjData(ObjData:TObjData);
      begin
        if ObjData.classtype<>FCObjData then
          Comment(V_Error,'Invalid input object format for '+ObjData.name+' got '+ObjData.classname+' expected '+FCObjData.classname);
        ObjDataList.Add(ObjData);
        ExecStack:=ExecStack or ObjData.ExecStack;
      end;


    procedure TExeOutput.Load_Start;
      begin
        ObjDataList.Clear;
        { Globals defined in the linker script }
        if not assigned(internalObjData) then
          internalObjData:=CObjData.create('*Internal*');
        AddObjData(internalObjData);
        { Common Data section }
        commonObjSection:=internalObjData.createsection(sec_bss,'');
      end;


    procedure TExeOutput.Load_EntryName(const aname:string);
      begin
        FEntryName:=aname;
      end;


    procedure TExeOutput.Load_IsSharedLibrary;
      begin
        IsSharedLibrary:=true;
      end;


    procedure TExeOutput.Load_ImageBase(const avalue:string);
      var
        code : integer;
        objsec : TObjSection;
        objsym : TObjSymbol;
        exesym : TExeSymbol;
      begin
        val(avalue,FImageBase,code);
        if code<>0 then
          Comment(V_Error,'Invalid number '+avalue);
        { Create __image_base__ symbol, create the symbol
          in a section with adress 0 and at offset 0 }
        objsec:=internalObjData.createsection('*__image_base__',0,[]);
        internalObjData.setsection(objsec);
        objsym:=internalObjData.SymbolDefine('__image_base__',AB_GLOBAL,AT_DATA);
        exesym:=texesymbol.Create(FExeSymbolList,objsym.name);
        exesym.ObjSymbol:=objsym;
      end;


    procedure TExeOutput.Load_Symbol(const aname:string);
      begin
        internalObjData.createsection('*'+aname,0,[]);
        internalObjData.SymbolDefine(aname,AB_GLOBAL,AT_DATA);
      end;

    procedure TExeOutput.Load_ProvideSymbol(const aname:string);
      begin
        if assigned(ExeSymbolList.Find(aname)) then
          exit;
        internalObjData.createsection('*'+aname,0,[]);
        // Use AB_COMMON to avoid muliple defined complaints
        internalObjData.SymbolDefine(aname,AB_COMMON,AT_DATA);
      end;


    procedure TExeOutput.Load_DynamicObject(ObjData:TObjData;asneeded:boolean);
      begin
      end;


    procedure TExeOutput.Order_Start;
      begin
      end;


    procedure TExeOutput.Order_End;
      begin
        internalObjData.afterwrite;
      end;


    procedure TExeOutput.Order_ExeSection(const aname:string);
      var
        sec : TExeSection;
      begin
        sec:=FindExeSection(aname);
        if not assigned(sec) then
          sec:=CExeSection.create(ExeSectionList,aname);
        { Clear ExeSection contents }
        FCurrExeSec:=sec;
      end;


    procedure TExeOutput.Order_EndExeSection;
      begin
        if not assigned(CurrExeSec) then
          internalerror(200602184);
        FCurrExeSec:=nil;
      end;


    procedure TExeOutput.Order_ObjSection(const aname:string);
      var
        i,j     : longint;
        ObjData : TObjData;
        objsec  : TObjSection;
        TmpObjSectionList : TFPObjectList;
      begin
        if not assigned(CurrExeSec) then
          internalerror(200602181);
        TmpObjSectionList:=TFPObjectList.Create(false);
        for i:=0 to ObjDataList.Count-1 do
          begin
            ObjData:=TObjData(ObjDataList[i]);
            for j:=0 to ObjData.ObjSectionList.Count-1 do
              begin
                objsec:=TObjSection(ObjData.ObjSectionList[j]);
                if (not objsec.Used) and
                   MatchPattern(aname,objsec.name) then
                  TmpObjSectionList.Add(objsec);
              end;
          end;
        { Order list if needed }
        Order_ObjSectionList(TmpObjSectionList,aname);
        { Add the (ordered) list to the current ExeSection }
        for i:=0 to TmpObjSectionList.Count-1 do
          begin
            objsec:=TObjSection(TmpObjSectionList[i]);
            CurrExeSec.AddObjSection(objsec);
          end;
        TmpObjSectionList.Free;
      end;


    procedure TExeOutput.Order_ObjSectionList(ObjSectionList : TFPObjectList; const aPattern:string);
      begin
      end;


    procedure TExeOutput.Order_Symbol(const aname:string);
      var
        objsym: TObjSymbol;
      begin
        objsym:=TObjSymbol(internalObjData.ObjSymbolList.Find(aname));
        if (objsym=nil) or (objsym.ObjSection.ObjData<>internalObjData) then
          internalerror(200603041);
        CurrExeSec.AddObjSection(objsym.ObjSection,True);
      end;

    procedure TExeOutput.Order_ProvideSymbol(const aname:string);
      var
        objsym : TObjSymbol;
        exesym : TExeSymbol;
      begin
        objsym:=TObjSymbol(internalObjData.ObjSymbolList.Find(aname));
        if (objsym=nil) or (objsym.ObjSection.ObjData<>internalObjData) then
          internalerror(2006030403);
        exesym:=TExeSymbol(ExeSymbolList.Find(aname));
        if not assigned(exesym) then
          internalerror(201206301);
        { Only include this section if it actually resolves
          the symbol }
        if exesym.objsymbol=objsym then
          CurrExeSec.AddObjSection(objsym.ObjSection,True);
      end;


    procedure TExeOutput.Order_Align(const avalue:string);
      var
        code     : integer;
        alignval : shortint;
        objsec   : TObjSection;
      begin
        val(avalue,alignval,code);
        if code<>0 then
          Comment(V_Error,'Invalid number '+avalue);
        if alignval<=0 then
          exit;
        { Create an empty section with the required aligning }
        inc(Fzeronr);
        objsec:=internalObjData.createsection('*align'+tostr(Fzeronr),alignval,CurrExeSec.SecOptions+[oso_Data,oso_keep]);
        CurrExeSec.AddObjSection(objsec);
      end;


    procedure TExeOutput.Order_Zeros(const avalue:string);
      var
        zeros : array[0..1023] of byte;
        code  : integer;
        len   : longint;
        objsec : TObjSection;
      begin
        val(avalue,len,code);
        if code<>0 then
          Comment(V_Error,'Invalid number '+avalue);
        if len<=0 then
          exit;
        if len>sizeof(zeros) then
          internalerror(200602254);
        fillchar(zeros,len,0);
        inc(Fzeronr);
        objsec:=internalObjData.createsection('*zeros'+tostr(Fzeronr),0,CurrExeSec.SecOptions+[oso_Data,oso_keep]);
        internalObjData.writebytes(zeros,len);
        CurrExeSec.AddObjSection(objsec);
      end;

    procedure TExeOutput.Order_Values(bytesize : aword; const avalue:string);
      const
        MAXVAL = 128;
      var
        bytevalues : array[0..MAXVAL-1] of byte;
        twobytevalues : array[0..MAXVAL-1] of word;
        fourbytevalues : array[0..MAXVAL-1] of dword;
        eightbytevalues : array[0..MAXVAL-1] of qword;
        allvals, oneval : string;
        len, commapos : longint;
        indexpos, code  : integer;
        anumval : qword;
        signedval : int64;
        objsec : TObjSection;
      begin
        indexpos:=0;
        allvals:=avalue;
        { avoid warnings }
        bytevalues[0]:=0;
        twobytevalues[0]:=0;
        fourbytevalues[0]:=0;
        eightbytevalues[0]:=0;
        repeat
          commapos:=pos(',',allvals);
          if commapos>0 then
            begin
              oneval:=trim(copy(allvals,1,commapos-1));
              allvals:=copy(allvals,commapos+1,length(allvals));
            end
          else
            begin
              oneval:=trim(allvals);
              allvals:='';
            end;
          if oneval<>'' then
            begin
              if oneval[1]='-' then
                begin
                  val(oneval,signedval,code);
                  anumval:=qword(signedval);
                end
              else
                val(oneval,anumval,code);
              if code<>0 then
                Comment(V_Error,'Invalid number '+avalue)
              else
                begin
                  if (indexpos<MAXVAL) then
                    begin
                      if source_info.endian<>target_info.endian then
                        swapendian(anumval);
                      { No range checking here }

                      if bytesize=1 then
                        bytevalues[indexpos]:=byte(anumval)
                      else if bytesize=2 then
                        twobytevalues[indexpos]:=word(anumval)
                      else if bytesize=4 then
                        fourbytevalues[indexpos]:=dword(anumval)
                      else if bytesize=8 then
                        eightbytevalues[indexpos]:=anumval;
                      inc(indexpos);
                    end
                  else
                    Comment(V_Error,'Buffer overrun in Order_values');
                end;
            end;
        until allvals='';
        if indexpos=0 then
          begin
            Comment(V_Error,'Invalid number '+avalue);
            exit;
          end;
        if indexpos=MAXVAL then
          begin
            Comment(V_Error,'Too many values '+avalue);
            internalerror(2006022505);
          end;
        len:=bytesize*indexpos;
        inc(Fvaluesnr);
        objsec:=internalObjData.createsection('*values'+tostr(Fvaluesnr),0,CurrExeSec.SecOptions+[oso_Data,oso_keep]);
        if bytesize=1 then
          internalObjData.writebytes(bytevalues,len)
        else if bytesize=2 then
          internalObjData.writebytes(twobytevalues,len)
        else if bytesize=4 then
          internalObjData.writebytes(fourbytevalues,len)
        else if bytesize=8 then
          internalObjData.writebytes(eightbytevalues,len);
        CurrExeSec.AddObjSection(objsec);
      end;


    procedure TExeOutput.MemPos_Start;
      begin
        CurrMemPos:=0;
        RemoveDisabledSections;
      end;


    procedure TExeOutput.MemPos_Header;
      begin
      end;


    procedure TExeOutput.MemPos_ExeSection(exesec:TExeSection);
      var
        i      : longint;
        objsec : TObjSection;
      begin
        { Alignment of ExeSection }
        CurrMemPos:=align_qword(CurrMemPos,MemAlign(exesec));
        exesec.MemPos:=CurrMemPos;

        { set position of object ObjSections }
        for i:=0 to exesec.ObjSectionList.Count-1 do
          begin
            objsec:=TObjSection(exesec.ObjSectionList[i]);
            CurrMemPos:=objsec.setmempos(CurrMemPos);
          end;

        { calculate size of the section }
        exesec.Size:=CurrMemPos-exesec.MemPos;
      end;


    procedure TExeOutput.MemPos_ExeSection(const aname:string);
      begin
        { Section can be removed }
        FCurrExeSec:=FindExeSection(aname);
        if not assigned(CurrExeSec) then
          exit;

        MemPos_ExeSection(CurrExeSec);
      end;


    procedure TExeOutput.MemPos_EndExeSection;
      begin
        if not assigned(CurrExeSec) then
          exit;
        FCurrExeSec:=nil;
      end;


    procedure TExeOutput.DataPos_Start;
      begin
      end;


    procedure TExeOutput.DataPos_Header;
      begin
      end;


    procedure TExeOutput.DataPos_ExeSection(exesec:TExeSection);
      begin
        { don't write normal section if writing only debug info }
        if (ExeWriteMode=ewm_dbgonly) and
           (exesec.SecOptions*[oso_debug,oso_debug_copy]=[]) then
          exit;

        if (oso_Data in exesec.SecOptions) then
          begin
            CurrDataPos:=align_aword(CurrDataPos,DataAlign(exesec));
            exesec.DataPos:=CurrDataPos;
            CurrDataPos:=CurrDataPos+exesec.Size;
          end;
      end;


    procedure TExeOutput.DataPos_ExeSection(const aname:string);
      begin
        { Section can be removed }
        FCurrExeSec:=FindExeSection(aname);
        if not assigned(CurrExeSec) then
          exit;
        DataPos_ExeSection(CurrExeSec);
      end;


    procedure TExeOutput.DataPos_EndExeSection;
      begin
        if not assigned(CurrExeSec) then
          exit;
        FCurrExeSec:=nil;
      end;


    procedure TExeOutput.DataPos_Symbols;
      begin
      end;


    procedure TExeOutput.BuildVTableTree(VTInheritList,VTEntryList:TFPObjectList);
      var
        hs : string;
        code : integer;
        i,k,
        vtableidx : longint;
        vtableexesym,
        childexesym,
        parentexesym : TExeSymbol;
        objsym : TObjSymbol;
      begin
        { Build inheritance tree from VTINHERIT }
        for i:=0 to VTInheritList.Count-1 do
          begin
            objsym:=TObjSymbol(VTInheritList[i]);
            hs:=objsym.name;
            { VTINHERIT_<ChildVMTName>$$<ParentVMTName> }
            Delete(hs,1,Pos('_',hs));
            k:=Pos('$$',hs);
            if k=0 then
              internalerror(200603311);
            childexesym:=texesymbol(FExeSymbolList.Find(Copy(hs,1,k-1)));
            parentexesym:=texesymbol(FExeSymbolList.Find(Copy(hs,k+2,length(hs)-k-1)));
            if not assigned(childexesym) or
               not assigned(parentexesym)then
              internalerror(200603312);
            if not assigned(childexesym.vtable) then
              begin
                childexesym.vtable:=TExeVTable.Create(childexesym);
                ExeVTableList.Add(childexesym.vtable);
              end;
            if not assigned(parentexesym.vtable) then
              begin
                parentexesym.vtable:=TExeVTable.Create(parentexesym);
                ExeVTableList.Add(parentexesym.vtable);
              end;
            childexesym.vtable.SetVTableSize(childexesym.ObjSymbol.Size);
            if parentexesym<>childexesym then
              parentexesym.vtable.AddChild(childexesym.vtable);
          end;

        { Find VTable entries from VTENTRY }
        for i:=0 to VTEntryList.Count-1 do
          begin
            objsym:=TObjSymbol(VTEntryList[i]);
            hs:=objsym.name;
            { VTENTRY_<VTableName>$$<Index> }
            Delete(hs,1,Pos('_',hs));
            k:=Pos('$$',hs);
            if k=0 then
              internalerror(200603319);
            vtableexesym:=texesymbol(FExeSymbolList.Find(Copy(hs,1,k-1)));
            val(Copy(hs,k+2,length(hs)-k-1),vtableidx,code);
            if (code<>0) then
              internalerror(200603318);
            if not assigned(vtableexesym) then
              internalerror(2006033110);
            vtableexesym.vtable.AddEntry(vtableidx);
          end;
      end;


    procedure TExeOutput.PackUnresolvedExeSymbols(const s:string);
      var
        i : longint;
        exesym : TExeSymbol;
      begin
        { Generate a list of Unresolved External symbols }
        for i:=0 to UnresolvedExeSymbols.count-1 do
          begin
            exesym:=TExeSymbol(UnresolvedExeSymbols[i]);
            if not (exesym.State in [symstate_undefined,symstate_undefweak]) then
              UnresolvedExeSymbols[i]:=nil;
          end;
        UnresolvedExeSymbols.Pack;
        Comment(V_Debug,'Number of unresolved externals '+s+' '+tostr(UnresolvedExeSymbols.Count));
      end;


    procedure TExeOutput.ResolveSymbols(StaticLibraryList:TFPObjectList);
      var
        ObjData   : TObjData;
        exesym    : TExeSymbol;
        objsym,
        commonsym : TObjSymbol;
        firstarchive,
        firstcommon : boolean;
        i         : longint;
        VTEntryList,
        VTInheritList : TFPObjectList;

        procedure LoadObjDataSymbols(ObjData:TObjData);
        var
          j      : longint;
          hs     : string;
          exesym : TExeSymbol;
          tmpsym,
          objsym : TObjSymbol;
          grp    : TObjSectionGroup;
          makeexternal : boolean;
        begin
          for j:=0 to ObjData.ObjSymbolList.Count-1 do
            begin
              objsym:=TObjSymbol(ObjData.ObjSymbolList[j]);
              { From the local symbols we are only interessed in the
                VTENTRY and VTINHERIT symbols }
              if objsym.bind=AB_LOCAL then
                begin
                  if cs_link_opt_vtable in current_settings.globalswitches then
                    begin
                      hs:=objsym.name;
                      if (hs[1]='V') then
                        begin
                          if Copy(hs,1,5)='VTREF' then
                            begin
                              if not assigned(objsym.ObjSection.VTRefList) then
                                objsym.ObjSection.VTRefList:=TFPObjectList.Create(false);
                              objsym.ObjSection.VTRefList.Add(objsym);
                            end
                          else if Copy(hs,1,7)='VTENTRY' then
                            VTEntryList.Add(objsym)
                          else if Copy(hs,1,9)='VTINHERIT' then
                            VTInheritList.Add(objsym);
                        end;
                    end;
                  continue;
                end;

              { If this symbol comes from COMDAT group, see if a group with
                matching signature is already included. }
              if assigned(objsym.objsection) and
                 assigned(objsym.objsection.group) then
                begin
                  grp:=objsym.objsection.group;
                  if grp.IsComdat then
                    begin
                      if ComdatGroups.Find(grp.name)=nil then
                        ComdatGroups.Add(grp.name,grp)
                      else
                        begin
                          { Undefine the symbol, causing relocations to it from same
                            objdata to be redirected to the symbol in the actually
                            linked group. }
                          if objsym.bind=AB_GLOBAL then
                            objsym.bind:=AB_EXTERNAL;
                          { AB_WEAK_EXTERNAL remains unchanged }
                          objsym.objsection:=nil;
                        end;
                    end;
                end;

              { Search for existing exesymbol }
              exesym:=texesymbol(FExeSymbolList.Find(objsym.name));
              if not assigned(exesym) then
                begin
                  exesym:=texesymbol.Create(FExeSymbolList,objsym.name);
                  exesym.ObjSymbol:=objsym;
                end
              else
                begin
                  if assigned(objsym.objsection) and assigned(exesym.objsymbol.objsection) then
                    begin
                      if (oso_comdat in exesym.ObjSymbol.objsection.SecOptions) and
                         (oso_comdat in objsym.objsection.SecOptions) then
                        begin
                          if exesym.ObjSymbol.objsection.ComdatSelection=objsym.objsection.ComdatSelection then
                            begin
                              makeexternal:=true;
                              case objsym.objsection.ComdatSelection of
                                oscs_none:
                                  makeexternal:=false;
                                oscs_any:
                                  Message1(link_d_comdat_discard_any,objsym.name);
                                oscs_same_size:
                                  if exesym.ObjSymbol.size<>objsym.size then
                                    Message1(link_e_comdat_size_differs,objsym.name)
                                  else
                                    Message1(link_d_comdat_discard_size,objsym.name);
                                oscs_exact_match:
                                  if (exesym.ObjSymbol.size<>objsym.size) and not exesym.ObjSymbol.objsection.Data.equal(objsym.objsection.Data) then
                                    Message1(link_e_comdat_content_differs,objsym.name)
                                  else
                                    Message1(link_d_comdat_discard_content,objsym.name);
                                oscs_associative:
                                  { this is handled in a different way }
                                  makeexternal:=false;
                                oscs_largest:
                                  if objsym.size>exesym.ObjSymbol.size then
                                    begin
                                      Message1(link_d_comdat_replace_size,objsym.name);
                                      { we swap the symbols and turn the smaller one to an external
                                        symbol }
                                      tmpsym:=exesym.objsymbol;
                                      exesym.objsymbol:=objsym;
                                      objsym.exesymbol:=exesym;
                                      objsym:=tmpsym;
                                    end;
                              end;
                              if makeexternal then
                                begin
                                  { Undefine the symbol, causing relocations to it from same
                                    objdata to be redirected to the symbol that is actually
                                    used }
                                  if objsym.bind=AB_GLOBAL then
                                    objsym.bind:=AB_EXTERNAL;
                                  { AB_WEAK_EXTERNAL remains unchanged }
                                  objsym.objsection:=nil;
                                end;
                            end
                          else
                            Message1(link_e_comdat_selection_differs,objsym.name);
                        end;
                    end;
                end;

              objsym.ExeSymbol:=exesym;
              case objsym.bind of
                AB_GLOBAL,
                AB_PRIVATE_EXTERN:
                  begin
                    if exesym.State<>symstate_defined then
                      begin
                        exesym.ObjSymbol:=objsym;
                        exesym.State:=symstate_defined;
                      end
                    else
                      Message1(link_e_duplicate_symbol,objsym.name);

                    { hidden symbols must become local symbols in the executable }
                    if objsym.bind=AB_PRIVATE_EXTERN then
                      objsym.bind:=AB_LOCAL;
                  end;
                AB_EXTERNAL :
                  begin
                    ExternalObjSymbols.add(objsym);
                    { Register unresolved symbols only the first time they
                      are registered }
                    if exesym.ObjSymbol=objsym then
                      UnresolvedExeSymbols.Add(exesym)
                    { Normal reference removes any existing "weakness" }
                    else if exesym.state=symstate_undefweak then
                      begin
                        exesym.state:=symstate_undefined;
                        exesym.ObjSymbol:=objsym;
                      end;
                  end;
                AB_COMMON :
                  begin
                    { A COMMON definition overrides weak one.
                      Also select the symbol with largest size. }
                    if (exesym.State in [symstate_undefined,symstate_undefweak,symstate_defweak]) or
                       ((exesym.State=symstate_common) and (objsym.size>exesym.ObjSymbol.size)) then
                      begin
                        exesym.ObjSymbol:=objsym;
                        exesym.State:=symstate_common;
                      end;
                    if assigned(objsym.objsection) and
                      (objsym.objsection.objdata=internalObjData) then
                      FProvidedObjSymbols.add(objsym)
                    else
                      CommonObjSymbols.add(objsym);
                  end;
                AB_WEAK_EXTERNAL :
                  begin
                    if objsym.objsection=nil then          { a weak reference }
                      begin
                        ExternalObjSymbols.add(objsym);
                        if exesym.ObjSymbol=objsym then
                          begin
                            UnresolvedExeSymbols.Add(exesym);
                            exesym.state:=symstate_undefweak;
                          end;
                      end
                    else                                   { a weak definition }
                      begin
                        if exesym.State in [symstate_undefined,symstate_undefweak] then
                          begin
                            exesym.ObjSymbol:=objsym;
                            exesym.state:=symstate_defweak;
                          end;
                      end;
                  end;
                else
                  internalerror(2019050510);
              end;
            end;
        end;

        procedure LoadLibrary(lib:TStaticLibrary);
          var
            j,k,oldcount: longint;
            members: TFPObjectList;
            exesym: TExeSymbol;
            objinput: TObjInput;
          begin
            case lib.Kind of
              lkArchive:
                begin
                  { Process list of Unresolved External symbols, we need
                    to use a while loop because the list can be extended when
                    we load members from the library. }
                  j:=0;
                  while (j<UnresolvedExeSymbols.count) do
                    begin
                      exesym:=TExeSymbol(UnresolvedExeSymbols[j]);
                      { Check first if the symbol is still undefined }
                      if (exesym.State=symstate_undefined) then
                        begin
                          if lib.ArReader.OpenFile(exesym.name) then
                            begin
                              if assigned(exemap) then
                                begin
                                  if firstarchive then
                                    begin
                                      exemap.Add('');
                                      exemap.Add('Archive member included because of file (symbol)');
                                      exemap.Add('');
                                      firstarchive:=false;
                                    end;
                                  exemap.Add(lib.ArReader.FileName+' - '+
                                    {exesym.ObjSymbol.ObjSection.FullName+}
                                    '('+exesym.Name+')');
                                end;
                              objinput:=lib.ObjInputClass.Create;
                              objinput.ReadObjData(lib.ArReader,objdata);
                              objinput.free;
                              AddObjData(objdata);
                              LoadObjDataSymbols(objdata);
                              lib.ArReader.CloseFile;
                            end;
                         end;
                      inc(j);
                    end;
                end;

              lkGroup:
                begin
                  { repeatedly process members of the group until no new
                    unresolved symbols appear }
                  members:=lib.GroupMembers;
                  repeat
                    oldcount:=UnresolvedExeSymbols.count;
                    for k:=0 to members.Count-1 do
                      LoadLibrary(TStaticLibrary(members[k]));
                  until UnresolvedExeSymbols.count=oldcount;
                end;
              lkObject:
                { TODO: ownership of objdata }
                //if lib.objdata.is_dynamic then
                  Load_DynamicObject(lib.objdata,lib.AsNeeded);
                {else
                  begin
                    AddObjData(lib.objdata);
                    LoadObjDataSymbols(lib.objdata);
                  end;}
            end;
          end;

      begin
        VTEntryList:=TFPObjectList.Create(false);
        VTInheritList:=TFPObjectList.Create(false);

        {
          The symbol resolving is done in 4 steps:
           1. Register symbols from objects
           2. Find symbols in static libraries
           3. Define symbols PROVIDEd by the link script
           4. Define still undefined common symbols
        }

        { Step 1, Register symbols from objects }
        for i:=0 to ObjDataList.Count-1 do
          begin
            ObjData:=TObjData(ObjDataList[i]);
            LoadObjDataSymbols(ObjData);
          end;
        PackUnresolvedExeSymbols('in objects');

        { Step 2, Find unresolved symbols in the libraries }
        firstarchive:=true;
        for i:=0 to StaticLibraryList.Count-1 do
          LoadLibrary(TStaticLibrary(StaticLibraryList[i]));

        PackUnresolvedExeSymbols('after static libraries');

        { Step 3, handle symbols provided in script }
        for i:=0 to FProvidedObjSymbols.count-1 do
          begin
            objsym:=TObjSymbol(FProvidedObjSymbols[i]);
            if objsym.exesymbol.State=symstate_defined then
              continue;
            objsym.exesymbol.objsymbol:=objsym;
            objsym.bind:=AB_GLOBAL;
            objsym.exesymbol.State:=symstate_defined;
          end;
        PackUnresolvedExeSymbols('after defining symbols provided by link script');

        { Step 4, Match common symbols or add to the globals }
        firstcommon:=true;
        for i:=0 to CommonObjSymbols.count-1 do
          begin
            objsym:=TObjSymbol(CommonObjSymbols[i]);
            if objsym.exesymbol.State=symstate_defined then
              begin
                if objsym.exesymbol.ObjSymbol.size<>objsym.size then
                  Comment(V_Debug,'Size of common symbol '+objsym.name+' is different, expected '+tostr(objsym.size)+' got '+tostr(objsym.exesymbol.ObjSymbol.size));
              end
            else
              begin
                { allocate new objsymbol in .bss of *COMMON* and assign
                  it to the exesymbol }
                if firstcommon then
                  begin
                    if assigned(exemap) then
                      exemap.AddCommonSymbolsHeader;
                    firstcommon:=false;
                  end;
                internalObjData.setsection(commonObjSection);
                { TODO: support alignment of common symbols (ELF targets at least),
                  increase commonObjSection.SecAlign if necessary here. }
                internalObjData.allocalign(used_align(size_2_align(objsym.size),0,commonObjSection.SecAlign));
                commonsym:=internalObjData.symboldefine(objsym.name,AB_GLOBAL,AT_DATA);
                commonsym.size:=objsym.size;
                internalObjData.alloc(objsym.size);
                if assigned(exemap) then
                  exemap.AddCommonSymbol(objsym);
                { Assign to the exesymbol }
                objsym.exesymbol.objsymbol:=commonsym;
                objsym.exesymbol.state:=symstate_defined;
              end;
          end;
        PackUnresolvedExeSymbols('after defining COMMON symbols');

        { Find entry symbol and print in map }
        if (EntryName<>'') then
          begin
            exesym:=texesymbol(ExeSymbolList.Find(EntryName));
            if assigned(exesym) then
              begin
                EntrySym:=exesym.ObjSymbol;
                if assigned(exemap) then
                  begin
                    exemap.Add('');
                    exemap.Add('Entry symbol '+EntryName);
                  end;
              end
            else
              Comment(V_Error,'Entrypoint '+EntryName+' not defined');
          end;

        { Generate VTable tree }
        if cs_link_opt_vtable in current_settings.globalswitches then
          BuildVTableTree(VTInheritList,VTEntryList);
        VTInheritList.Free;
        VTEntryList.Free;
      end;


    procedure TExeOutput.GenerateDebugLink(const dbgname:string;dbgcrc:cardinal);
      var
        debuglink : array[0..1023] of byte;
        len   : longint;
        objsec : TObjSection;
        exesec : TExeSection;
      begin
        { From the gdb manual  chapter 15. GDB Files:

           * A filename, with any leading directory components removed, followed by a zero byte,
           * zero to three bytes of padding, as needed to reach the next four-byte boundary within the section, and
           * a four-byte CRC checksum, stored in the same endianness used for the executable file itself. The checksum is computed
             on the debugging information file's full contents by the function given below, passing zero as the crc argument.
        }
        fillchar(debuglink,sizeof(debuglink),0);
        len:=0;
        move(dbgname[1],debuglink[len],length(dbgname));
        inc(len,length(dbgname)+1);
        len:=align(len,4);
        if source_info.endian<>target_info.endian then
          SwapEndian(dbgcrc);
        move(dbgcrc,debuglink[len],sizeof(cardinal));
        inc(len,4);
        { Add section }
        exesec:=FindExeSection(debuglinkname);
        if not assigned(exesec) then
          exesec:=CExeSection.create(ExeSectionList,debuglinkname);
        exesec.SecOptions:=[oso_data,oso_keep];
        exesec.SecAlign:=4;
        objsec:=internalObjData.createsection(exesec.name,1,exesec.SecOptions);
        internalObjData.writebytes(debuglink,len);
        exesec.AddObjSection(objsec);
      end;


    procedure TExeOutput.GenerateLibraryImports(ImportLibraryList:TFPHashObjectList);
      begin
      end;


    procedure TExeOutput.MarkTargetSpecificSections(WorkList:TFPObjectList);
      begin
      end;


    procedure TExeOutput.AfterUnusedSectionRemoval;
      begin
      end;


    function ByAddress(item1,item2:pointer):longint;
      var
        sym1:TObjSymbol absolute item1;
        sym2:TObjSymbol absolute item2;
      begin
        if sym1.address>sym2.address then
          result:=1
        else if sym1.address<sym2.address then
          result:=-1
        else
          result:=0;
      end;


    procedure TExeOutput.PrintMemoryMap;
      var
        exesec : TExeSection;
        objsec : TObjSection;
        objsym : TObjSymbol;
        i,j,k,m: longint;
        list   : TFPList;
        flag   : boolean;
      begin
        if not assigned(exemap) then
          exit;
        { create a list of symbols sorted by address }
        list:=TFPList.Create;
        list.Capacity:=ExeSymbolList.Count;
        for i:=0 to ExeSymbolList.Count-1 do
          list.Add(TExeSymbol(ExeSymbolList[i]).ObjSymbol);
        list.Sort(@ByAddress);

        exemap.AddMemoryMapHeader(ImageBase);
        k:=0;
        for i:=0 to ExeSectionList.Count-1 do
          begin
            exesec:=TExeSection(ExeSectionList[i]);
            exemap.AddMemoryMapExeSection(exesec);
            for j:=0 to exesec.ObjSectionList.count-1 do
              begin
                objsec:=TObjSection(exesec.ObjSectionList[j]);
                exemap.AddMemoryMapObjectSection(objsec);

                while (k<list.Count) and (TObjSymbol(list[k]).Address<objsec.MemPos) do
                  inc(k);
                while (k<list.Count)  do
                  begin
                    objsym:=TObjSymbol(list[k]);
                    if objsym.address>objsec.MemPos+objsec.Size then
                      break;
                    if objsym.objsection=objsec then
                      exemap.AddMemoryMapSymbol(objsym)
                    else
                      begin
                        { Got a symbol with address falling into current section, but
                          belonging to a different section. This may happen for zero-length
                          sections because symbol list is sorted by address but not by section.
                          Do some look-ahead in this case. }
                        m:=k+1;
                        flag:=false;
                        while (m<list.Count) and (TObjSymbol(list[m]).Address=objsym.address) do
                          begin
                            if TObjSymbol(list[m]).objsection=objsec then
                              begin
                                flag:=true;
                                list.Exchange(k,m);
                                exemap.AddMemoryMapSymbol(TObjSymbol(list[k]));
                                break;
                              end;
                            inc(m);
                          end;
                        if not flag then
                          break;
                      end;
                    inc(k);
                  end;
              end;
          end;
        list.Free;
      end;


    procedure TExeOutput.FixupSymbols;

        procedure UpdateSymbol(objsym:TObjSymbol);
        begin
          objsym.bind:=objsym.ExeSymbol.ObjSymbol.bind;
          objsym.offset:=objsym.ExeSymbol.ObjSymbol.offset;
          objsym.size:=objsym.ExeSymbol.ObjSymbol.size;
          objsym.typ:=objsym.ExeSymbol.ObjSymbol.typ;
          objsym.ObjSection:=objsym.ExeSymbol.ObjSymbol.ObjSection;
          objsym.group:=objsym.ExeSymbol.ObjSymbol.group;
        end;

      var
        i      : longint;
        objsym : TObjSymbol;
        exesym : TExeSymbol;
      begin
        { Print list of Unresolved External symbols }
        if not AllowUndefinedSymbols then
          for i:=0 to UnresolvedExeSymbols.count-1 do
            begin
              exesym:=TExeSymbol(UnresolvedExeSymbols[i]);
              if (exesym.State=symstate_undefined) then
                begin
                  if assigned(exesym.ObjSymbol) and assigned(exesym.ObjSymbol.ObjData) then
                    Message2(link_e_undefined_symbol_in_obj,exesym.name,exesym.objsymbol.ObjData.Name)
                  else
                    Message1(link_e_undefined_symbol,exesym.name);
                end;
            end;

        {
          Fixing up symbols is done in the following steps:
           1. Update common references
           2. Update external references

           Symbols with objsection<>nil are removed from the lists,
           remaining ones can be processed later by calling this method again.
        }

        { Step 1, Update commons. Preserve the original symbol size and bind,
          this is needed for correct relocation of DJCOFF files. }
        for i:=0 to CommonObjSymbols.count-1 do
          begin
            objsym:=TObjSymbol(CommonObjSymbols[i]);
            if objsym.bind<>AB_COMMON then
              internalerror(200606241);

            objsym.ObjSection:=objsym.ExeSymbol.ObjSymbol.ObjSection;
            objsym.offset:=objsym.ExeSymbol.ObjSymbol.offset;
            objsym.typ:=objsym.ExeSymbol.ObjSymbol.typ;
          end;

        { Step 2, Update externals }
        for i:=0 to ExternalObjSymbols.count-1 do
          begin
            objsym:=TObjSymbol(ExternalObjSymbols[i]);
            if not (objsym.bind in [AB_EXTERNAL,AB_WEAK_EXTERNAL]) then
              internalerror(200606242);
            UpdateSymbol(objsym);
            { Collect symbols that resolve to indirect functions,
              they will need additional target-specific processing. }
            if objsym.typ=AT_GNU_IFUNC then
              IndirectObjSymbols.Add(objsym)
            else if assigned(objsym.objsection) then
              ExternalObjSymbols[i]:=nil;
          end;
        CommonObjSymbols.Clear;
        ExternalObjSymbols.Pack;
      end;


    procedure TExeOutput.MergeStabs;
      var
        stabexesec,
        stabstrexesec : TExeSection;
        relocsec,
        currstabsec,
        currstabstrsec,
        mergedstabsec,
        mergedstabstrsec : TObjSection;
        hstabreloc,
        currstabreloc : TObjRelocation;
        i,j : longint;
        currstabrelocidx,
        mergestabcnt,
        stabcnt : longword;
        skipstab : boolean;
        skipfun : boolean;
        hstab   : TObjStabEntry;
        stabrelocofs : longword;
        buf     : array[0..1023] of byte;
        bufend,
        bufsize  : longint;
      begin
        stabexesec:=FindExeSection('.stab');
        stabstrexesec:=FindExeSection('.stabstr');
        if (stabexesec=nil) or
           (stabstrexesec=nil) or
           (stabexesec.ObjSectionlist.count=0) then
          exit;
        { Create new stabsection }
        stabRelocofs:=pbyte(@hstab.nvalue)-pbyte(@hstab);
        mergedstabsec:=internalObjData.CreateSection(sec_stab,'');
        mergedstabstrsec:=internalObjData.CreateSection(sec_stabstr,'');

        { write stab for hdrsym }
        mergedstabsec.writeZeros(sizeof(TObjStabEntry));
        mergestabcnt:=1;

        { .stabstr starts with a #0 }
        buf[0]:=0;
        mergedstabstrsec.write(buf[0],1);

        skipfun:=false;
        { Copy stabs and corresponding Relocations }
        for i:=0 to stabexesec.ObjSectionList.Count-1 do
          begin
            currstabsec:=TObjSection(stabexesec.ObjSectionList[i]);
            currstabstrsec:=currstabsec.ObjData.findsection('.stabstr');
            if assigned(currstabstrsec) then
              begin
                stabcnt:=currstabsec.Data.size div sizeof(TObjStabEntry);
                currstabsec.Data.seek(0);
                currstabrelocidx:=0;
                for j:=0 to stabcnt-1 do
                  begin
                    hstabreloc:=nil;
                    skipstab:=false;
                    currstabsec.Data.read(hstab,sizeof(TObjStabEntry));
                    MaybeSwapStab(hstab);
                    { Only include first hdrsym stab }
                    if hstab.ntype=0 then
                      skipstab:=true;
                    if skipfun then
                      begin
                        { Skip all stabs for function body until N_RBRAC }
                        skipfun:=hstab.ntype<>N_RBRAC;
                        skipstab:=true;
                      end;
                    if not skipstab then
                      begin
                        { Find corresponding Relocation }
                        currstabreloc:=nil;
                        while (currstabrelocidx<longword(currstabsec.ObjRelocations.Count)) do
                          begin
                            currstabreloc:=TObjRelocation(currstabsec.ObjRelocations[currstabrelocidx]);
                            if assigned(currstabreloc) and
                               (currstabreloc.dataoffset>=longword(j)*sizeof(TObjStabEntry)+stabrelocofs) then
                              break;
                            inc(currstabrelocidx);
                          end;
                        if assigned(currstabreloc) and
                           (currstabreloc.dataoffset=longword(j)*sizeof(TObjStabEntry)+stabrelocofs) then
                          begin
                            hstabReloc:=currstabReloc;
                            inc(currstabrelocidx);
                          end;

                        { Check if the stab is refering to a removed section }
                        if assigned(hstabreloc) then
                          begin
                            if assigned(hstabreloc.Symbol) then
                              relocsec:=hstabreloc.Symbol.ObjSection
                            else
                              relocsec:=hstabreloc.ObjSection;
                            if not assigned(relocsec) then
                              internalerror(200603302);
                            if not relocsec.Used then
                              begin
                                skipstab:=true;
                                if (hstab.ntype=N_Function) and (hstab.strpos<>0) then
                                  begin
                                    currstabstrsec.Data.seek(hstab.strpos);
                                    bufsize:=currstabstrsec.Data.read(buf,sizeof(buf));
                                    bufend:=indexbyte(buf,bufsize,Ord(':'));
                                    if (bufend<>-1) and (bufend<bufsize-1) and (buf[bufend+1]=Ord('F')) then
                                      skipfun:=true;
                                  end;
                              end;
                          end;
                      end;
                    if not skipstab then
                      begin
                        { Copy string in stabstr }
                        if hstab.strpos<>0 then
                          begin
                            currstabstrsec.Data.seek(hstab.strpos);
                            hstab.strpos:=mergedstabstrsec.Size;
                            repeat
                              bufsize:=currstabstrsec.Data.read(buf,sizeof(buf));
                              bufend:=indexbyte(buf,bufsize,0);
                              if bufend=-1 then
                                bufend:=bufsize
                              else
                                begin
                                  { include the #0 }
                                  inc(bufend);
                                end;
                              mergedstabstrsec.write(buf,bufend);
                            until (buf[bufend-1]=0) or (bufsize<sizeof(buf));
                          end;
                        { Copy and Update the relocation }
                        if assigned(hstabreloc) then
                          begin
                            hstabreloc.Dataoffset:=mergestabcnt*sizeof(TObjStabEntry)+stabRelocofs;
                            { Remove from List without freeing the object }
                            currstabsec.ObjRelocations.List[currstabrelocidx-1]:=nil;
                            mergedstabsec.ObjRelocations.Add(hstabreloc);
                          end;
                        { Write updated stab }
                        MaybeSwapStab(hstab);
                        mergedstabsec.write(hstab,sizeof(hstab));
                        inc(mergestabcnt);
                      end;
                  end;
              end;

            { Unload stabs }
            if assigned(currstabstrsec) then
              begin
                currstabstrsec.Used:=False;
                currstabstrsec.ReleaseData;
              end;
            currstabsec.Used:=false;
            currstabsec.ReleaseData;
          end;

        { Generate new HdrSym }
        if mergedstabsec.Size>0 then
          begin
            hstab.strpos:=1;
            hstab.ntype:=0;
            hstab.nother:=0;
            hstab.ndesc:=word(mergestabcnt-1);
            hstab.nvalue:=mergedstabstrsec.Size;
            MaybeSwapStab(hstab);
            mergedstabsec.Data.seek(0);
            mergedstabsec.Data.write(hstab,sizeof(hstab));
          end;

        { Replace all sections with our combined stabsec }
        stabexesec.ObjSectionList.Clear;
        stabstrexesec.ObjSectionList.Clear;
        stabexesec.AddObjSection(mergedstabsec);
        stabstrexesec.AddObjSection(mergedstabstrsec);
      end;


    procedure TExeOutput.MarkEmptySections;
      var
        i, j   : longint;
        exesec : TExeSection;
        doremove : boolean;
      begin
        for i:=0 to ExeSectionList.Count-1 do
          begin
            exesec:=TExeSection(ExeSectionList[i]);

            doremove:=not(oso_keep in exesec.SecOptions) and
                (
                 (exesec.ObjSectionlist.count=0) or
                 (
                  (cs_link_strip in current_settings.globalswitches) and
                  not(cs_link_separate_dbg_file in current_settings.globalswitches) and
                  (oso_debug in exesec.SecOptions)
                 )
                );
            if not doremove then
              begin
               { Check if section has no actual data }
                doremove:=true;
                for j:=0 to exesec.ObjSectionList.Count-1 do
                  if TObjSection(exesec.ObjSectionList[j]).Size<>0 then
                    begin
                      doremove:=false;
                      break;
                    end;
              end;
            if doremove then
              begin
                Comment(V_Debug,'Disabling empty section '+exesec.name);
                exesec.Disabled:=true;
              end;
          end;
      end;


    procedure TExeOutput.RemoveDisabledSections;
      var
        i: longint;
        exesec: TExeSection;
      begin
        for i:=0 to ExeSectionList.Count-1 do
          begin
            exesec:=TExeSection(ExeSectionList[i]);
            if exesec.Disabled then
              ExeSectionList[i]:=nil;
          end;
        ExeSectionList.Pack;
      end;


    procedure TExeOutput.RemoveDebugInfo;
      var
        i      : longint;
        exesec : TExeSection;
      begin
        for i:=0 to ExeSectionList.Count-1 do
          begin
            exesec:=TExeSection(ExeSectionList[i]);
            if (oso_debug in exesec.SecOptions) then
              ExeSectionList[i]:=nil;
          end;
        ExeSectionList.Pack;
      end;


    procedure TExeOutput.RemoveUnreferencedSections;
      var
        ObjSectionWorkList : TFPObjectList;

        procedure AddToObjSectionWorkList(aobjsec:TObjSection);
        begin
          if not aobjsec.Used then
            begin
              aobjsec.Used:=true;
              ObjSectionWorkList.Add(aobjsec);
            end;
        end;

        procedure DoReloc(objreloc:TObjRelocation);
        var
          objsym : TObjSymbol;
          refobjsec : TObjSection;
          refgrp : TObjSectionGroup;
        begin
          { Disabled Relocation to 0  }
          if (objreloc.flags and rf_nosymbol)<>0 then
            exit;
          refobjsec:=nil;
          refgrp:=nil;
          if assigned(objreloc.symbol) then
            begin
              objsym:=objreloc.symbol;
              if objsym.bind<>AB_LOCAL then
                begin
                  if not assigned(objsym.exesymbol) then
                    internalerror(200603063);
                  objsym.exesymbol.used:=true;
                  objsym:=objsym.exesymbol.objsymbol;
                end;
              if not assigned(objsym.objsection) then
                exit
              else
                refobjsec:=objsym.objsection;
            end
          else if assigned(objreloc.objsection) then
            refobjsec:=objreloc.objsection
          else if assigned(objreloc.group) then
            refgrp:=objreloc.group
{$ifdef WASM}
          else if objreloc.ftype=Ord(RELOC_TYPE_INDEX_LEB) then
            {nothing}
{$endif WASM}
          else
            internalerror(200603316);
          if assigned(exemap) then
            begin
              objsym:=objreloc.symbol;
              if assigned(objsym) and (objsym.typ<>AT_SECTION) then
                exemap.Add('  References  '+objsym.name+' in '
                  +refobjsec.fullname)
              else if assigned(refobjsec) then
                exemap.Add('  References '+refobjsec.fullname)
              else if assigned(refgrp) then
                exemap.Add('  References '+refgrp.Name)
{$ifdef WASM}
              else if objreloc.ftype=Ord(RELOC_TYPE_INDEX_LEB) then
                {nothing}
{$endif WASM}
              else
                internalerror(2006033111);
            end;
          if assigned(refobjsec) then
            AddToObjSectionWorkList(refobjsec);
        end;

        procedure DoVTableRef(vtable:TExeVTable;VTableIdx:longint);
        var
          i : longint;
          objreloc : TObjRelocation;
        begin
          objreloc:=vtable.VTableRef(VTableIdx);
          if assigned(objreloc) then
            begin
              { Process the relocation now if the ObjSection is
                already processed and marked as used. Otherwise we leave it
                unprocessed. It'll then be resolved when the ObjSection is
                changed to Used }
              if vtable.ExeSymbol.ObjSymbol.ObjSection.Used then
                DoReloc(objreloc);
            end;
          { This recursive walking is done here instead of
            in TExeVTable.VTableRef because we can now process
            all needed relocations }
          for i:=0 to vtable.ChildList.Count-1 do
            DoVTableRef(TExeVTable(vtable.ChildList[i]),VTableIdx);
        end;

        procedure ProcessWorkList;
        var
          hs        : string;
          i,k       : longint;
          objsec    : TObjSection;
          objsym    : TObjSymbol;
          code      : integer;
          vtableidx : longint;
          vtableexesym : TExeSymbol;
        begin
          while ObjSectionWorkList.Count>0 do
            begin
              objsec:=TObjSection(ObjSectionWorkList.Last);
              if not assigned(objsec.exesection) then
                internalerror(202102001);
              if assigned(exemap) then
                exemap.Add('Keeping '+objsec.FullName+' '+ToStr(objsec.ObjRelocations.Count)+' references');
              ObjSectionWorkList.Delete(ObjSectionWorkList.Count-1);

              { Process Relocations }
              for i:=0 to objsec.ObjRelocations.count-1 do
                DoReloc(TObjRelocation(objsec.ObjRelocations[i]));

              { Process Virtual Entry calls }
              if cs_link_opt_vtable in current_settings.globalswitches then
                begin
                  for i:=0 to objsec.VTRefList.count-1 do
                    begin
                      objsym:=TObjSymbol(objsec.VTRefList[i]);
                      hs:=objsym.name;
                      Delete(hs,1,Pos('_',hs));
                      k:=Pos('$$',hs);
                      if k=0 then
                        internalerror(200603314);
                      vtableexesym:=texesymbol(FExeSymbolList.Find(Copy(hs,1,k-1)));
                      val(Copy(hs,k+2,length(hs)-k-1),vtableidx,code);
                      if (code<>0) then
                        internalerror(200603317);
                      if not assigned(vtableexesym) then
                        internalerror(200603315);
                      if not assigned(vtableexesym.vtable) then
                        internalerror(2006033112);
                      DoVTableRef(vtableexesym.vtable,vtableidx);
                    end;
                end;
            end;

        end;

      var
        i,j       : longint;
        exesec    : TExeSection;
        objdata   : TObjData;
        objsec    : TObjSection;
      begin
        ObjSectionWorkList:=TFPObjectList.Create(false);

        if assigned(exemap) then
          exemap.AddHeader('Removing unreferenced sections');

        { Initialize by marking all sections unused and
          adding the sections with oso_keep flags to the ObjSectionWorkList }
        for i:=0 to ObjDataList.Count-1 do
          begin
            ObjData:=TObjData(ObjDataList[i]);
            for j:=0 to ObjData.ObjSectionList.Count-1 do
              begin
                objsec:=TObjSection(ObjData.ObjSectionList[j]);
                objsec.Used:=false;
{ TODO: remove debug section always keep}
                if oso_debug in objsec.secoptions then
                  objsec.Used:=true;
                if (oso_keep in objsec.secoptions) then
                  begin
                    AddToObjSectionWorkList(objsec);
                    if objsec.name='.fpc.n_links' then
                      objsec.Used:=false;
                  end;
              end;
          end;
        if assigned(entrysym) then
          AddToObjSectionWorkList(entrysym.exesymbol.objsymbol.objsection);

        { Process all sections, add new sections to process based
          on the symbol references  }
        ProcessWorkList;

        { Handle stuff like .pdata, i.e. sections that are not referenced
          but must be included if sections they reference are included.
          Loop is necessary because .pdata can reference (via .xdata)
          more text sections, VMTs of exception classes, etc. }
        repeat
          MarkTargetSpecificSections(ObjSectionWorkList);
          if (ObjSectionWorkList.Count=0) then
            break;
          ProcessWorkList;
        until False;

        ObjSectionWorkList.Free;
        ObjSectionWorkList:=nil;

        { Remove unused objsections from ExeSectionList }
        for i:=0 to ExeSectionList.Count-1 do
          begin
            exesec:=TExeSection(ExeSectionList[i]);
            for j:=0 to exesec.ObjSectionlist.count-1 do
              begin
                objsec:=TObjSection(exesec.ObjSectionlist[j]);
                if not objsec.used then
                  begin
                    if assigned(exemap) then
                      exemap.Add('Removing '+objsec.FullName);
                    exesec.ObjSectionlist[j]:=nil;
                    objsec.ReleaseData;
                  end;
              end;
            exesec.ObjSectionlist.Pack;
          end;
      end;


    procedure TExeOutput.FixupRelocations;
      var
        i,j     : longint;
        exesec  : TExeSection;
        objsec  : TObjSection;
      begin
        for i:=0 to ExeSectionList.Count-1 do
          begin
            exesec:=TExeSection(ExeSectionList[i]);
            if not assigned(exesec) then
              continue;
            for j:=0 to exesec.ObjSectionlist.count-1 do
              begin
                objsec:=TObjSection(exesec.ObjSectionlist[j]);
                if not objsec.Used then
                  internalerror(200603301);
                if (objsec.ObjRelocations.Count>0) and
                   not assigned(objsec.data) then
                  internalerror(2002051801);
                DoRelocationFixup(objsec);
                {for size = 0 data is not valid PM }
                if assigned(objsec.data) and (objsec.data.size<>objsec.size) then
                  internalerror(2010092801,'wrong data size for '+objsec.FullName);
              end;
          end;
      end;


    procedure TExeOutput.RemoveUnusedExeSymbols;
      var
        i : longint;
        sym : TExeSymbol;
      begin
        { Removing unused symbols }
        for i:=0 to ExeSymbolList.Count-1 do
          begin
            sym:=TExeSymbol(ExeSymbolList[i]);
            { an unresolved weak symbol has objsection=nil }
            if assigned(sym.ObjSymbol.objsection) and
              (not sym.ObjSymbol.objsection.Used) then
              ExeSymbolList[i]:=nil;
          end;
        ExeSymbolList.Pack;
      end;


    procedure TExeOutput.SetCurrMemPos(const AValue: qword);
      begin
        if AValue>MaxMemPos then
          Message1(link_f_executable_too_big, target_os_string);
        FCurrMemPos:=AValue;
      end;


    procedure TExeOutput.WriteExeSectionContent;
      var
        exesec : TExeSection;
        objsec : TObjSection;
        i,j    : longint;
        dpos,pad: aword;
      begin
        for j:=0 to ExeSectionList.Count-1 do
          begin
            exesec:=TExeSection(ExeSectionList[j]);
            { don't write normal section if writing only debug info }
            if (ExeWriteMode=ewm_dbgonly) and
               (exesec.SecOptions*[oso_debug,oso_debug_copy]=[]) then
              continue;

            if oso_data in exesec.SecOptions then
              begin
                if exesec.DataPos<FWriter.Size then
                  InternalError(2012103002);
                FWriter.Writezeros(exesec.DataPos-FWriter.Size);
                for i:=0 to exesec.ObjSectionList.Count-1 do
                  begin
                    objsec:=TObjSection(exesec.ObjSectionList[i]);
                    if oso_data in objsec.secoptions then
                      begin
                        if not assigned(objsec.data) then
                          internalerror(2006030404);
                        dpos:=objsec.MemPos-exesec.MemPos+exesec.DataPos;
                        pad:=dpos-FWriter.Size;
                        { objsection must be within SecAlign bytes from the previous one }
                        if (dpos<FWriter.Size) or
                          (pad>=max(objsec.SecAlign,1)) then
                          internalerror(2006022503);
                        FWriter.writeZeros(pad);
                        FWriter.writearray(objsec.data);
                      end;
                  end;
              end;
          end;
      end;


    procedure TExeOutput.ReplaceExeSectionList(newlist: TFPList);
      var
        tmp: TFPHashObjectList;
        i: longint;
      begin
        tmp:=TFPHashObjectList.Create(true);
        for i:=0 to newlist.count-1 do
          TFPHashObject(newlist[i]).ChangeOwner(tmp);
        { prevent destruction of existing sections }
        for i:=0 to ExeSectionList.count-1 do
          ExeSectionList.List[i]:=nil;
        FExeSectionList.Free;
        FExeSectionList:=tmp;
      end;


{****************************************************************************
                                TObjInput
****************************************************************************}

    constructor TObjInput.create;
      begin
      end;


    procedure TObjInput.inputerror(const s : string);
      begin
        Comment(V_Error,s+' while reading '+InputFileName);
      end;


    class function TObjInput.CanReadObjData(AReader:TObjectReader):boolean;
      begin
        result:=false;
      end;


    procedure TObjInput.ReadSectionContent(Data:TObjData);
      var
        i: longint;
        sec: TObjSection;
      begin
        for i:=0 to Data.ObjSectionList.Count-1 do
          begin
            sec:=TObjSection(Data.ObjSectionList[i]);
            { Skip debug sections }
            if (oso_debug in sec.SecOptions) and
               (cs_link_strip in current_settings.globalswitches) and
               not(cs_link_separate_dbg_file in current_settings.globalswitches) then
              continue;

            if assigned(sec.Data) then
              begin
                FReader.Seek(sec.datapos);
                if not FReader.ReadArray(sec.data,sec.Size) then
                  begin
                    InputError('Can''t read object data');
                    exit;
                  end;
              end;
          end;
      end;


{$ifdef MEMDEBUG}
initialization
  memobjsymbols:=TMemDebug.create('ObjSymbols');
  memobjsymbols.stop;
  memobjsections:=TMemDebug.create('ObjSections');
  memobjsections.stop;

finalization
  memobjsymbols.free;
  memobjsections.free;
{$endif MEMDEBUG}
end.