Since cd1d61c44f (make union merge an xdl merge favor, 2010-03-01), we
pass NULL to ll_xdl_merge() for the "name" labels of the ancestor, ours
and theirs buffers. We usually use these for annotating conflict markers
left in a file. For a union merge, these shouldn't matter; the point of
it is that we'd never leave conflict markers in the first place.
But there is one code path where we may dereference them: if the file
contents appear to be binary, ll_binary_merge() will give up and pass
them to warning() to generate a message for the user (that was true even
when cd1d61c44f was written, though the warning was in ll_xdl_merge()
back then).
That can result in a segfault, though on many systems (including glibc),
the printf routines will helpfully just say "(null)" instead. We can
extend our binary-union test in t6406 to check stderr, which catches the
problem on all systems.
This also fixes a warning from "gcc -O3". Unlike lower optimization
levels, it inlines enough to see that the NULL can make it to warning()
and complains:
In function ‘ll_binary_merge’,
inlined from ‘ll_xdl_merge’ at ll-merge.c:115:10,
inlined from ‘ll_union_merge’ at ll-merge.c:151:9:
ll-merge.c:74:4: warning: ‘%s’ directive argument is null [-Wformat-overflow=]
74 | warning("Cannot merge binary files: %s (%s vs. %s)",
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
75 | path, name1, name2);
| ~~~~~~~~~~~~~~~~~~~
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
ll-merge.c | 2 +-
t/t6406-merge-attr.sh | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/ll-merge.c b/ll-merge.c
index 145deb12fa..0ee34d8a01 100644
--- a/ll-merge.c
+++ b/ll-merge.c
@@ -151,7 +151,7 @@ static int ll_union_merge(const struct ll_merge_driver *drv_unused,
o = *opts;
o.variant = XDL_MERGE_FAVOR_UNION;
return ll_xdl_merge(drv_unused, result, path_unused,
- orig, NULL, src1, NULL, src2, NULL,
+ orig, orig_name, src1, name1, src2, name2,
&o, marker_size);
}
diff --git a/t/t6406-merge-attr.sh b/t/t6406-merge-attr.sh
index c1c458d933..8494645837 100755
--- a/t/t6406-merge-attr.sh
+++ b/t/t6406-merge-attr.sh
@@ -221,7 +221,8 @@ test_expect_success 'binary files with union attribute' '
printf "two\0" >bin.txt &&
git commit -am two &&
- test_must_fail git merge bin-main
+ test_must_fail git merge bin-main 2>stderr &&
+ grep -i "warning.*cannot merge.*HEAD vs. bin-main" stderr
'
test_done
--
2.32.0.529.g079a794268
