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-|*************************************************************************
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-|* *
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-|* DSTART.S Startup module for Pascal programs using dLibs *
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-|* *
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-|*************************************************************************
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-
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-|*
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-|* entry points
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-|*
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-.globl __base | basepage pointer
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-.globl __start | startup entry point
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-.globl _etext | end of text segment
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-.globl _edata | end of data segment
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-.globl _end | end of BSS segment (end of program)
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-.globl __BREAK | location of stack/heap break
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-.globl __ARGC | number of arguments
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-.globl __ARGS | argument list pointer
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-.globl __envp | environment string pointer
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-.globl _errno | system error number
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-
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-|
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-| external references
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-|
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-|.globl __stklen | Stack size value from C (unsigned long)
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-
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-|
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-| useful constants
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-|
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-MINSTK = 16384 | Minimum 16K stack size
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-MARGIN = 512 | Minimum memory to return to OS
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-
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-|
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-| GEMDOS functions
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-|
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-Cconws = 0x09 | Console write string
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-Pterm = 0x4C | Process terminate (with exit code)
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-Mshrink = 0x4A | Shrink program space
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-
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-|
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-| basepage offsets
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-|
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-p_hitpa = 0x04 | top of TPA
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-p_tbase = 0x08 | base of text
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-p_tlen = 0x0C | length of text
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-p_dbase = 0x10 | base of data
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-p_dlen = 0x14 | length of data
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-p_bbase = 0x18 | base of BSS
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-p_blen = 0x1C | length of BSS
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-p_env = 0x2C | environment string
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-p_cmdlin = 0x80 | command line image
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-
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-|
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-| STARTUP ROUTINE (must be first object in link)
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-|
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-.text
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- .globl start
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- .globl _start
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-
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-__start:
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-start:
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-_start:
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-|
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-| save initial stack and basepage pointers
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-|
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- movel sp,a5 | a5 = initial stack pointer
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- movel sp@(4),a4 | a4 = basepage address
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- movel a4,__base
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- movel a4@(p_tbase),d3
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- addl a4@(p_tlen),d3
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- movel d3,_etext | end of text segment
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- movel a4@(p_dbase),d3
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- addl a4@(p_dlen),d3
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- movel d3,_edata | end of data segment
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- movel a4@(p_bbase),d3
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- addl a4@(p_blen),d3
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- movel d3,_end | end of BSS (end of program)
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- movel d3,__BREAK; | set initial _break value
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- movel a4@(p_env),__envp | save environment pointer
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-|
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-| call C function to get command line arguments
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-|
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- lea a4@(p_cmdlin),a0 | get pointer to command line image
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- moveb a0@+,d0
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- extw d0 | extract length
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-| movew d0,sp@- | cmdlen
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-| movel a0,sp@- | cmdline
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-| jsr __initar | call _initargs(cmdline, cmdlen)
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-| addql #6,sp
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- movew d0,__ARGC | save length
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- movel a0,__ARGS | save pointer to string
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-|
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-| calculate free space available to program
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-|
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- movel __BREAK,d3
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- movel d3,a3 | a3 = base of free space
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- negl d3
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- addl a4@(p_hitpa),d3
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- subl #MARGIN,d3 | d3 = free space
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-|
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-| calculate new stack size (store in d2)
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-|
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-| ASSUME 8K STACK FOR THE MOMENT.
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- movel __stklen,d2 | d2 = _STKSIZ
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- tstl d2 | if __STKSIZ is zero
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- beq minimum | use MINSTK
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- bra setstk | use __STKSIZ
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-minimum:
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- movel #MINSTK,d2 | use MINSTK
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-|
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-| check to see if there is enough room for requested stack
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-|
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-setstk:
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- cmpl d3,d2
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- blt shrink | if (available < requested)
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- movel #stkerr,sp@-
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- movew #Cconws,sp@-
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- trap #1 | report a stack error
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- addql #6,sp
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- movew #-39,sp@-
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- movew #Pterm,sp@-
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- trap #1 | and return error -39 (ENSMEM)
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-|
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-| set up new stack pointer and Mshrink
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-shrink:
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- addl a3,d2 | new stack = free base + stack size
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- movel d2,sp
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- subl a4,d2 | keep space = new stack - __base
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- movel d2,sp@-
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- movel a4,sp@-
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- clrw sp@-
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- movew #Mshrink,sp@-
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- trap #1 | Mshrink(0, _base, keep);
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- addl #12,sp
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-|
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-| call C entry point function _main()
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-|
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- jsr PASCALMAIN | if _main returns
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-
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- movew #0,sp@- | Terminate program normally
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- trap #1
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-
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-| movew d0,sp@(4) | insert return value and fall thru
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-
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-
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-
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-|
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-| check for stack overflow (done after all OS traps)
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-|
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-chkstk:
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- cmpl __BREAK,sp
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- bgt nosweat | if (_break > sp)
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- movel #stkovf,sp@-
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- movew #Cconws,sp@-
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- trap #1 | report a stack overflow
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- addql #6,sp
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- movew #-1,sp@-
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- movew #Pterm,sp@-
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- trap #1 | and return error -1 (ERROR)
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-nosweat:
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- movel traprtn,sp@- | else, restore return address
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- rts | and do a normal return.
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-
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-|
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-| this call to _main ensures that it the user's main() function will be
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-| linked, even if it is in a library.
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-|
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- jsr PASCALMAIN | NO PATH TO THIS STATEMENT
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- movew d0,sp@-
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- movew #0x4c,sp@-
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- trap #1
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-
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-
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-|
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-| initialized data space
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-|
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-.data
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-.even
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-stkerr: | not enough memory for stack
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- .ascii "Not enough memory"
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- .byte 0x0d,0x0a,0x00
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-stkovf: | impending stack overflow
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- .ascii "Stack overflow"
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- .byte 0x0d,0x0a,0x00
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-.even
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-_errno: | system error number
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- .word 0
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-__ARGC: | number of command line args
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- .word 0
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-__ARGS: | pointer to command line arg list
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- .long 0
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-|
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-| uninitialized data space
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-|
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-.even
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-__base: | pointer to basepage
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- .long 0
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-_etext: | pointer to end of text segment
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- .long 0
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-_edata: | pointer to end of data segment
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- .long 0
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-_end: | pointer to end of BSS (end of program)
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- .long 0
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-__BREAK: | pointer to stack/heap break
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- .long 0
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-__envp: | pointer to environment string
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- .long 0
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-traprtn: | storage for return PC in trap hooks
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- .long 0
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Karoly Balogh