Cast 64 bit off_t to 32 bit size_t

Some systems have sizeof(off_t) == 8 while sizeof(size_t) == 4.
This implies that we are able to access and work on files whose
maximum length is around 2^63-1 bytes, but we can only malloc or
mmap somewhat less than 2^32-1 bytes of memory.

On such a system an implicit conversion of off_t to size_t can cause
the size_t to wrap, resulting in unexpected and exciting behavior.
Right now we are working around all gcc warnings generated by the
-Wshorten-64-to-32 option by passing the off_t through xsize_t().

In the future we should make xsize_t on such problematic platforms
detect the wrapping and die if such a file is accessed.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/diffcore-break.c b/diffcore-break.c
index acb18db..9c19b8c 100644
--- a/diffcore-break.c
+++ b/diffcore-break.c
@@ -89,7 +89,7 @@ static int should_break(struct diff_filespec *src,
 	 * merge the surviving pair together if the score is
 	 * less than the minimum, after rename/copy runs.
 	 */
-	*merge_score_p = src_removed * MAX_SCORE / src->size;
+	*merge_score_p = (int)(src_removed * MAX_SCORE / src->size);
 
 	/* Extent of damage, which counts both inserts and
 	 * deletes.