The pointer p is dereferenced and we get an unsigned char. Before
shifting it's automatically promoted to int. Left-shifting a signed
32-bit value bigger than 127 by 24 places is undefined. Explicitly
convert to a 32-bit unsigned type to avoid undefined behaviour if
the highest bit is set.
Found with Clang's UBSan.
Signed-off-by: Rene Scharfe <l.s.r@xxxxxx>
---
compat/bswap.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/compat/bswap.h b/compat/bswap.h
index d47c003544..4582c1107a 100644
--- a/compat/bswap.h
+++ b/compat/bswap.h
@@ -166,10 +166,10 @@ static inline uint64_t git_bswap64(uint64_t x)
(*((unsigned char *)(p) + 0) << 8) | \
(*((unsigned char *)(p) + 1) << 0) )
#define get_be32(p) ( \
- (*((unsigned char *)(p) + 0) << 24) | \
- (*((unsigned char *)(p) + 1) << 16) | \
- (*((unsigned char *)(p) + 2) << 8) | \
- (*((unsigned char *)(p) + 3) << 0) )
+ ((uint32_t)*((unsigned char *)(p) + 0) << 24) | \
+ ((uint32_t)*((unsigned char *)(p) + 1) << 16) | \
+ ((uint32_t)*((unsigned char *)(p) + 2) << 8) | \
+ ((uint32_t)*((unsigned char *)(p) + 3) << 0) )
#define put_be32(p, v) do { \
unsigned int __v = (v); \
*((unsigned char *)(p) + 0) = __v >> 24; \
--
2.13.3
