Re: Segfault with merge-tree on multiple Git versions

On Wed, Mar 27, 2013 at 04:53:27PM +0100, thomas wrote:

Charlie Smurthwaite [off-list ref] writes:

quoted

I am experiencing a segmentation fault in various versions of Git using
different repositories. Specifically, I have reproduced it using a
public repo and the latest stable Git version. Other repos trigger the
error on different versions.

Full info can be found below. Thanks,

Charlie


Test repository:
https://github.com/atech/mail

Test Command
git merge-tree 26bb22a052fef9f74063afd4fc6fc11fe200b19f
8d6bdf012941d876b2279994e02f1bb0d5c26e7d
d5ef97ac407d945f231cd7c8fb1cfe48b3a12083

I happened to walk past on IRC and found I could easily reproduce it, so
I bisected:

  35ffe7583108ab236dcf81226690388491d9962f is the first bad commit
  commit 35ffe7583108ab236dcf81226690388491d9962f
  Author: Junio C Hamano [off-list ref]
  Date:   Thu Dec 13 15:51:29 2012 -0800

      merge-tree: fix d/f conflicts
      
      The previous commit documented two known breakages revolving around
      a case where one side flips a tree into a blob (or vice versa),
      where the original code simply gets confused and feeds a mixture of
      trees and blobs into either the recursive merge-tree (and recursing
      into the blob will fail) or three-way merge (and merging tree contents
      together with blobs will fail).
      
      Fix it by feeding trees (and only trees) into the recursive
      merge-tree machinery and blobs (and only blobs) into the three-way
      content level merge machinery separately; when this happens, the
      entire merge has to be marked as conflicting at the structure level.
      
      Signed-off-by: Junio C Hamano [off-list ref]

Looks like a simple typo in merge-tree.c::unresolved:

-- >8 --
merge-tree: fix typo in merge-tree.c::unresolved

When calculating whether there is a d/f conflict, the calculation of
whether both sides are directories generates an incorrect references
mask because it does not use the loop index to set the correct bit.
Fix this typo.

Signed-off-by: John Keeping <redacted>

diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
index e0d0b7d..bc912e3 100644
--- a/builtin/merge-tree.c
+++ b/builtin/merge-tree.c

@@ -245,7 +245,7 @@ static void unresolved(const struct traverse_info *info, struct name_entry n[3])
 	unsigned dirmask = 0, mask = 0;
 
 	for (i = 0; i < 3; i++) {
-		mask |= (1 << 1);
+		mask |= (1 << i);
 		if (n[i].mode && S_ISDIR(n[i].mode))
 			dirmask |= (1 << i);
 	}