[Cmake-commits] CMake branch, next, updated. v2.8.10.2-1141-gbc201e3

[David Cole]

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- Log -----------------------------------------------------------------
http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=bc201e3dcc00121c5854ba619a7d6a23e2bf4360
commit bc201e3dcc00121c5854ba619a7d6a23e2bf4360
Merge: 3a045a8 6a6a6f3
Author:     David Cole <david.cole at kitware.com>
AuthorDate: Fri Nov 30 08:06:26 2012 -0500
Commit:     CMake Topic Stage <kwrobot at kitware.com>
CommitDate: Fri Nov 30 08:06:26 2012 -0500

    Merge topic 'avoid-undefined-behavior' into next
    
    6a6a6f3 libarchive: fixed undefined left shift with signed ints
    e0af55a CMake Nightly Date Stamp


http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=6a6a6f36707f9588249990eb2d67e414d2eebd38
commit 6a6a6f36707f9588249990eb2d67e414d2eebd38
Author:     Sean McBride <sean at rogue-research.com>
AuthorDate: Thu Nov 29 18:20:11 2012 -0500
Commit:     David Cole <david.cole at kitware.com>
CommitDate: Fri Nov 30 08:04:48 2012 -0500

    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.

diff --git a/Utilities/cmlibarchive/libarchive/archive_endian.h b/Utilities/cmlibarchive/libarchive/archive_endian.h
index bbf58fd..3c039f7 100644
--- a/Utilities/cmlibarchive/libarchive/archive_endian.h
+++ b/Utilities/cmlibarchive/libarchive/archive_endian.h
@@ -64,7 +64,13 @@ archive_be16dec(const void *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
@@ -72,7 +78,15 @@ archive_be32dec(const void *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
@@ -88,7 +102,13 @@ archive_le16dec(const void *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
@@ -96,7 +116,15 @@ archive_le32dec(const void *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

-----------------------------------------------------------------------

Summary of changes:
 Source/CMakeVersion.cmake                          |    2 +-
 Utilities/cmlibarchive/libarchive/archive_endian.h |   36 +++++++++++++++++--
 2 files changed, 33 insertions(+), 5 deletions(-)


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