@matheusbsbs / matheus-bagliano / commits / b80741e5b9

stable-qsort: avoid using potentially unaligned access

Like in the previous patch for compat/qsort_s.c, remove the optimization of using an on-stack buffer to avoid small allocations. This ensures maximum alignment for the array elements and simplifies the code a bit. The performance impact for the current callers is unlikely to be noticeable: * compat/mingw.c::make_environment_block() uses ALLOC_ARRAY and ALLOC_GROW several times already, so another allocation of up to 1KB should not matter much. * diffcore-rename.c::diffcore_rename_extended() is called once per diff or twice per merge, and those require allocations for each object and more already. * merge-ort.c::detect_and_process_renames() is called once per merge. It's responsible for the two per-merge diffcore_rename_extended() calls mentioned above as well, though. So this is possibly the most impacted caller. Per-object allocations are likely to dwarf the additional small allocations in git_stable_qsort(), though. Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>

René Scharfe committed Jan 8, 2022 at 00:30 UTC b80741e5b9c6b47a6f802ffdb0bba87357b35a9f

1 file changed +5 -11

stable-qsort.c

+5 -11

index 6cbaf39f7b..7ff12467cd 100644 --- a/stable-qsort.c +++ b/stable-qsort.c @@ -48,15 +48,9 @@ void git_stable_qsort(void *b, size_t n, size_t s, int (*cmp)(const void *, const void *)) { const size_t size = st_mult(n, s); - char buf[1024]; - - if (size < sizeof(buf)) { - /* The temporary array fits on the small on-stack buffer. */ - msort_with_tmp(b, n, s, cmp, buf); - } else { - /* It's somewhat large, so malloc it. */ - char *tmp = xmalloc(size); - msort_with_tmp(b, n, s, cmp, tmp); - free(tmp); - } + char *tmp; + + tmp = xmalloc(size); + msort_with_tmp(b, n, s, cmp, tmp); + free(tmp); }