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...ointing to the start of > the prefix data) > > this will yield: > > $ clang test.s -dead_strip > ld: warning: N_ALT_ENTRY bit set on first atom in section __TEXT/__text > And the prefix data will be stripped again. > > E.g. what you end up getting is: > > $ otool -vVtdj a.out > a.out: > _main: > 0000000100000fb5 ff c0 incl %eax > 0000000100000fb7 c3 retq > > instead of what we’d like to get: > > otool -vVtdj a.out > a.out: > _main.dsp: > 0000000100000fb1 01 00 addl %eax, (%rax) > 0000000100000...

...ms to do the trick! > > $ cat test.s > .section __TEXT,__text > .globl _main > > .long 1 > _main: > inc %eax > ret > > .alt_entry _main > _main.dsp = _main-4 > > .subsections_via_symbols > > > $ clang test.s -dead_strip > $ otool -vVtdj a.out > a.out: > _main.dsp: > 0000000100000fb1 01 00 addl %eax, (%rax) > 0000000100000fb3 00 00 addb %al, (%rax) > _main: > 0000000100000fb5 ff c0 incl %eax > 0000000100000fb7 c3 retq > > > > However, now I need to fig...

...gt; > .globl _main > > > > .long 1 > > _main: > > inc %eax > > ret > > > > .alt_entry _main > > _main.dsp = _main-4 > > > > .subsections_via_symbols > > > > > > $ clang test.s -dead_strip > > $ otool -vVtdj a.out > > a.out: > > _main.dsp: > > 0000000100000fb1 01 00 addl %eax, (%rax) > > 0000000100000fb3 00 00 addb %al, (%rax) > > _main: > > 0000000100000fb5 ff c0 incl %eax > > 0000000100000fb7 c3 retq > > &...

That is in theory what omitting the .subsections_via_symbols directive is supposed to do, but in an experiment I ran a year or two ago I found that the Mach-O linker was still dead stripping on symbol boundaries with this directive omitted. In any case, a more precise approach has more recently (~a few months ago) become possible. There is a relatively new asm directive called .altentry that, as