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@@ -2859,8 +2859,61 @@ unit cgx86;
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begin
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{$ifdef i8086}
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+ { Win16 callback/exported proc prologue support.
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+ Since callbacks can be called from different modules, DS on entry may be
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+ initialized with the data segment of a different module, so we need to
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+ get ours. But we can't do
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+
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+ push ds
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+ mov ax, dgroup
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+ mov ds, ax
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+
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+ because code segments are shared between different instances of the same
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+ module (which have different instances of the current program's data segment),
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+ so the same 'mov ax, dgroup' instruction will be used for all instances
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+ of the program and it will load the same segment into ax.
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+
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+ So, the standard win16 prologue looks like this:
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+
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+ mov ax, ds
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+ nop
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+ inc bp
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+ push bp
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+ mov bp, sp
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+ push ds
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+ mov ds, ax
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+
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+ By default, this does nothing, except wasting a few extra machine cycles and
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+ destroying ax in the process. However, Windows checks the first three bytes
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+ of every exported function and if they are 'mov ax,ds/nop', they are replaced
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+ with nop/nop/nop. Then the MakeProcInstance api call should be used to create
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+ a thunk that loads ds for the current program instance in ax before calling
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+ the routine.
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+
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+ And now the fun part comes: somebody (Michael Geary) figured out that all this
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+ crap was unnecessary, because in Win16 exe modules, we always have DS=SS, so we
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+ can simply initialize DS from SS :) And then calling MakeProcInstance becomes
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+ unnecessary. This is what "smart callbacks" (cs_win16_smartcallbacks) do. However,
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+ this only works for exe files, not for dlls, because dlls run with DS<>SS. There's
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+ another solution for dlls - since win16 dlls only have a single instance of their
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+ data segment, we can initialize ds from dgroup. However, there's not a single
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+ solution for both exe and dlls, so we don't know what to use e.g. in a unit. So,
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+ that's why there's still an option to turn smart callbacks off and go the
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+ MakeProcInstance way.
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+
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+ Additional details here: http://www.geary.com/fixds.html }
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+ if (current_settings.x86memorymodel<>mm_huge) and
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+ (po_exports in current_procinfo.procdef.procoptions) and
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+ (target_info.system=system_i8086_win16) then
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+ begin
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+ if cs_win16_smartcallbacks in current_settings.moduleswitches then
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+ list.concat(Taicpu.Op_reg_reg(A_MOV,S_W,NR_SS,NR_AX))
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+ else
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+ list.concat(Taicpu.Op_reg_reg(A_MOV,S_W,NR_DS,NR_AX));
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+ list.concat(Taicpu.op_none(A_NOP));
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+ end
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{ interrupt support for i8086 }
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- if po_interrupt in current_procinfo.procdef.procoptions then
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+ else if po_interrupt in current_procinfo.procdef.procoptions then
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begin
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list.concat(Taicpu.Op_reg(A_PUSH,S_W,NR_AX));
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list.concat(Taicpu.Op_reg(A_PUSH,S_W,NR_BX));
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@@ -2941,7 +2994,9 @@ unit cgx86;
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else
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begin
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{$ifdef i8086}
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- if (ts_x86_far_procs_push_odd_bp in current_settings.targetswitches) and
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+ if ((ts_x86_far_procs_push_odd_bp in current_settings.targetswitches) or
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+ ((po_exports in current_procinfo.procdef.procoptions) and
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+ (target_info.system=system_i8086_win16))) and
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is_proc_far(current_procinfo.procdef) then
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cg.a_op_const_reg(list,OP_ADD,OS_ADDR,1,current_procinfo.framepointer);
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{$endif i8086}
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@@ -2983,8 +3038,16 @@ unit cgx86;
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end;
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{$ifdef i8086}
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- if (current_settings.x86memorymodel=mm_huge) and
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- not (po_interrupt in current_procinfo.procdef.procoptions) then
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+ { win16 exported proc prologue follow-up (see the huge comment above for details) }
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+ if (current_settings.x86memorymodel<>mm_huge) and
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+ (po_exports in current_procinfo.procdef.procoptions) and
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+ (target_info.system=system_i8086_win16) then
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+ begin
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+ list.concat(Taicpu.op_reg(A_PUSH,S_W,NR_DS));
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+ list.concat(Taicpu.Op_reg_reg(A_MOV,S_W,NR_AX,NR_DS));
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+ end
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+ else if (current_settings.x86memorymodel=mm_huge) and
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+ not (po_interrupt in current_procinfo.procdef.procoptions) then
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begin
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list.concat(Taicpu.op_reg(A_PUSH,S_W,NR_DS));
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reference_reset(fardataseg,0);
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@@ -2992,6 +3055,16 @@ unit cgx86;
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list.concat(Taicpu.Op_ref_reg(A_MOV,S_W,fardataseg,NR_AX));
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list.concat(Taicpu.Op_reg_reg(A_MOV,S_W,NR_AX,NR_DS));
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end;
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+ { SI and DI are volatile in the BP7 and FPC's pascal calling convention,
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+ but must be preserved in Microsoft C's pascal calling convention, and
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+ since Windows is compiled with Microsoft compilers, these registers
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+ must be saved for exported procedures (BP7 for Win16 also does this). }
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+ if (po_exports in current_procinfo.procdef.procoptions) and
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+ (target_info.system=system_i8086_win16) then
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+ begin
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+ list.concat(Taicpu.Op_reg(A_PUSH,S_W,NR_SI));
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+ list.concat(Taicpu.Op_reg(A_PUSH,S_W,NR_DI));
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+ end;
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{$endif i8086}
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{$ifdef i386}
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nickysn