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/builtin-count-objects.c b/builtin-count-objects.c
index f5b22bb80..6263d8af2 100644
--- a/builtin-count-objects.c
+++ b/builtin-count-objects.c
@@ -44,7 +44,7 @@ static void count_objects(DIR *d, char *path, int len, int verbose,
 			if (lstat(path, &st) || !S_ISREG(st.st_mode))
 				bad = 1;
 			else
-				(*loose_size) += st.st_blocks;
+				(*loose_size) += xsize_t(st.st_blocks);
 		}
 		if (bad) {
 			if (verbose) {