Appvars / Discussion

This is the discussion related to the wiki page Appvars.

Appvars

Xeda Elnara 12 Mar 2013 19:36

In the last tutorial we pointed out that you can not create permanent self modifying code.

This is bugging me because you definitely can do this. The OS leaves the name of the executing program in OP1, so you can do something like:

     bcall(_ChkFindSym)
     ld hl,smc_num-9D95h+4   ;+4 because DE points tot he size bytes and 2 bytes are the header BB6Dh
     add hl,de
     ld e,(hl)
     inc hl
     ld d,(hl)
     inc de
     ld (hl),d
     dec hl
     ld (hl),e
     ex de,hl
     bcall(_DispHL)
     ret
smc_num:
     .dw 0

Note that this won't work on the uncompressed hex codes, so you need to either make sure to use AsmComp() or have it compiled by some compiler.

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