Re: git-merge-recursive segmentation error

[Shawn Pearce <spearce@spearce.org>]

Luben Tuikov <ltuikov@yahoo.com> wrote:
> --- Linus Torvalds <torvalds@osdl.org> wrote:
> > Can you run that by hand under gdb and get a backtrace?
> 
> Linus,
> 
> Auto-merging init/Kconfig
> Auto-merging init/version.c
> 
> Program received signal SIGSEGV, Segmentation fault.
> xdl_merge (orig=Variable "orig" is not available.
> ) at xdiff/xmerge.c:200
> 200                     t2.ptr = (char *)xe2->xdf2.recs[m->i2]->ptr;
> (gdb) bt
> #0  xdl_merge (orig=Variable "orig" is not available.
> ) at xdiff/xmerge.c:200
> #1  0x000000000040322c in merge_file (o=0x7fffd4f762f0, a=0x7fffd4f76270, b=0x7fffd4f762b0,
> branch1=0x7fffd4f77976 "HEAD", 
>     branch2=0x7fffd4f7797b "cc016448b0bf0764928275d034e367753bde8162") at merge-recursive.c:667
> #2  0x0000000000404e87 in merge_trees (head=0x12e4a00, merge=0x555328, common=0x555350,
> branch1=Variable "branch1" is not available.
> ) at merge-recursive.c:1074
> #3  0x0000000000405376 in merge (h1=0x5452f0, h2=0x545370, branch1=0x7fffd4f77976 "HEAD",
> branch2=0x7fffd4f7797b "cc016448b0bf0764928275d034e367753bde8162", call_depth=0, 
>     ancestor=0x5453f0, result=0x7fffd4f764e0) at merge-recursive.c:1245
> #4  0x00000000004056a5 in main (argc=Variable "argc" is not available.
> ) at merge-recursive.c:1312
> 
> I also ran git-bisect twice over two well known but overlapping
> good-bad regions and I get the same commit as being the culprit.
> It seems to be commit 1510fea781cb0517eeba8c378964f7bc4f9577ab.

Oww, the finger points at me!  :-)

Hmm.  1510fe does not look right to me.  That return 0 should only
be activating when FAST_WORKING_DIRECTORY == 0, so you really want
this patch below.  Normally NO_FAST_WORKING_DIRECTORY is _not_
defined, which means FAST_WORKING_DIRECTORY == 1, and in that case
the if should always be false and the compiler should be stripping
the code out entirely.

What's odd is that the xdl_merge routine is crashing out because
this code activated.  It really should not have, so more work is
still required...

diff --git a/diff.c b/diff.c
index 77ba641..1c1de11 100644
--- a/diff.c
+++ b/diff.c
@@ -1194,7 +1194,7 @@ static int reuse_worktree_file(const char *name, const unsigned char *sha1, int
 	 * objects however would tend to be slower as they need
 	 * to be individually opened and inflated.
 	 */
-	if (FAST_WORKING_DIRECTORY && !want_file && has_sha1_pack(sha1, NULL))
+	if (!FAST_WORKING_DIRECTORY && !want_file && has_sha1_pack(sha1, NULL))
 		return 0;