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src: make sort order deterministic, next try

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We cannot compare pointers as they may point to qsort-local objects.
And we must make sure that cmp(a,b) always agrees with cmp(b,a).
This commit is contained in:
Markus F.X.J. Oberhumer
2023-08-30 16:41:59 +02:00
parent f4e5b29708
commit cfa8107ab9
5 changed files with 54 additions and 24 deletions
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src/p_mach.cpp
+17 -2
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@@ -562,7 +562,8 @@ PackMachBase<T>::compare_segment_command(void const *const aa, void const *const
unsigned const xb = b->cmd - lc_seg;
if (xa < xb) return -1; // LC_SEGMENT first
if (xa > xb) return 1;
if (0 != xa) return 0; // not LC_SEGMENT
// mfx @jreiser: we do not want to return 0; please check
//// if (0 != xa) return 0; // not LC_SEGMENT
// Ascending by .fileoff so that find_SEGMENT_gap works
if (a->fileoff < b->fileoff)
return -1;
@@ -572,10 +573,24 @@ PackMachBase<T>::compare_segment_command(void const *const aa, void const *const
if (a->vmaddr < b->vmaddr) return -1;
if (a->vmaddr > b->vmaddr) return 1;
// Descending by .vmsize
// mfx @jreiser: I think this may violate cmp(a,b) == -cmp(b,a); please check
// if ((a->vmsize != 0) != (b->vmsize != 0))
// return (a->vmsize != 0) ? -1 : 1;
if (a->vmsize) return -1; // 'a' is first
if (b->vmsize) return 1; // 'a' is last
// What could remain?
return aa < bb ? -1 : 1; // make sort order deterministic/stable
#define CMP(field) \
if (a->field != b->field) return a->field < b->field ? -1 : 1
// try to make sort order deterministic and just compare more fields
CMP(vmsize);
CMP(cmdsize);
CMP(filesize);
CMP(maxprot);
CMP(initprot);
CMP(nsects);
CMP(flags);
#undef CMP
return 0;
}
// At 2013-02-03 part of the source for codesign was