Re: [PATCH] bisect: save heap memory. allocate only the required amount
From: Jeff King <hidden>
Date: 2016-06-15 23:02:20
Subsystem:
the rest · Maintainer:
Linus Torvalds
On Sun, Aug 24, 2014 at 07:47:24PM +0530, Arjun Sreedharan wrote:
quoted hunk ↗ jump to hunk
diff --git a/bisect.c b/bisect.c index d6e851d..c96aab0 100644 --- a/bisect.c +++ b/bisect.c@@ -215,10 +215,13 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n } qsort(array, cnt, sizeof(*array), compare_commit_dist); for (p = list, i = 0; i < cnt; i++) { - struct name_decoration *r = xmalloc(sizeof(*r) + 100); + char name[100]; + sprintf(name, "dist=%d", array[i].distance); + int name_len = strlen(name); + struct name_decoration *r = xmalloc(sizeof(*r) + name_len);
This allocation should be name_len + 1 for the NUL-terminator, no? It looks like add_name_decoration in log-tree already handles half of what you are adding here. Can we just make that available globally (it is manipulating the already-global "struct decoration name_decoration")? I also notice that we do not set r->type at all, meaning the decoration lookup code in log-tree will access uninitialized memory (worse, it will use it as a pointer offset into the color list; I got a segfault when I tried to run "git rev-list --bisect-all v1.8.0..v1.9.0"). I think we need this:
diff --git a/bisect.c b/bisect.c
index d6e851d..e2a7682 100644
--- a/bisect.c
+++ b/bisect.c@@ -219,6 +219,7 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n struct object *obj = &(array[i].commit->object); sprintf(r->name, "dist=%d", array[i].distance); + r->type = 0; r->next = add_decoration(&name_decoration, obj, r); p->item = array[i].commit; p = p->next;
at a minimum. It looks like this was a regression caused by eb3005e (commit.h: add 'type' to struct name_decoration, 2010-06-19). Which makes me wonder if anybody actually _uses_ --bisect-all (which AFAICT is the only way to trigger the problem), but since it's public, I guess we should keep it. I think the sane thing here is to stop advertising name_decoration as a global, and make all callers use add_name_decoration. That makes it easier for callers like this one, and would have caught the regression caused be eb3005e (the compiler would have noticed that we were not passing a type parameter to the function). -Peff