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libarchive: fixed undefined left shift with signed ints 

caught by clang's -fsanitize=shift. A small unsigned int was
promoted, according to C's regular promotion rules, to a signed
int, it was then left shifted.  This sometimes pushed a 1 into
the sign bit, which is undefined behaviour. Fixed by using
unsigned temporaries.
This commit is contained in:
Sean McBride 2012-11-29 18:20:11 -05:00 committed by David Cole
parent e0af55a5f4
commit 6a6a6f3670
1 changed files with 32 additions and 4 deletions
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36
Utilities/cmlibarchive/libarchive/archive_endian.h
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@ -64,7 +64,13 @@ archive_be16dec(const void *pp)
{ {
unsigned char const *p = (unsigned char const *)pp; unsigned char const *p = (unsigned char const *)pp;
return ((p[0] << 8) | p[1]); /* Store into unsigned temporaries before left shifting, to avoid
promotion to signed int and then left shifting into the sign bit,
which is undefined behaviour. */
unsigned int p1 = p[1];
unsigned int p0 = p[0];
return ((p0 << 8) | p1);
} }
static inline uint32_t static inline uint32_t
@ -72,7 +78,15 @@ archive_be32dec(const void *pp)
{ {
unsigned char const *p = (unsigned char const *)pp; unsigned char const *p = (unsigned char const *)pp;
return ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]); /* Store into unsigned temporaries before left shifting, to avoid
promotion to signed int and then left shifting into the sign bit,
which is undefined behaviour. */
unsigned int p3 = p[3];
unsigned int p2 = p[2];
unsigned int p1 = p[1];
unsigned int p0 = p[0];
return ((p0 << 24) | (p1 << 16) | (p2 << 8) | p3);
} }
static inline uint64_t static inline uint64_t
@ -88,7 +102,13 @@ archive_le16dec(const void *pp)
{ {
unsigned char const *p = (unsigned char const *)pp; unsigned char const *p = (unsigned char const *)pp;
return ((p[1] << 8) | p[0]); /* Store into unsigned temporaries before left shifting, to avoid
promotion to signed int and then left shifting into the sign bit,
which is undefined behaviour. */
unsigned int p1 = p[1];
unsigned int p0 = p[0];
return ((p1 << 8) | p0);
} }
static inline uint32_t static inline uint32_t
@ -96,7 +116,15 @@ archive_le32dec(const void *pp)
{ {
unsigned char const *p = (unsigned char const *)pp; unsigned char const *p = (unsigned char const *)pp;
return ((p[3] << 24) | (p[2] << 16) | (p[1] << 8) | p[0]); /* Store into unsigned temporaries before left shifting, to avoid
promotion to signed int and then left shifting into the sign bit,
which is undefined behaviour. */
unsigned int p3 = p[3];
unsigned int p2 = p[2];
unsigned int p1 = p[1];
unsigned int p0 = p[0];
return ((p3 << 24) | (p2 << 16) | (p1 << 8) | p0);
} }
static inline uint64_t static inline uint64_t