From b80741e5b9c6b47a6f802ffdb0bba87357b35a9f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ren=C3=A9=20Scharfe?= Date: Sat, 8 Jan 2022 00:30:44 +0100 Subject: [PATCH] stable-qsort: avoid using potentially unaligned access MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Junio C Hamano --- stable-qsort.c | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-) diff --git a/stable-qsort.c b/stable-qsort.c 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]; + char *tmp; - 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); - } + tmp = xmalloc(size); + msort_with_tmp(b, n, s, cmp, tmp); + free(tmp); }