Implement a warning for known shift overflows on constant shift

expressions. Consider the code:

  int64_t i = 10 << 30;

This compiles fine, but most developers expect it to produce the value
for 10 gigs, not -2 gigs. This is actually undefined behavior because
the LHS is a signed integer type.

The warning is currently gated behind -Wshift-overflow.

There is a special case where only the sign bit is overridden that gets
a custom error message and is by default ignored. This case is much less
likely to cause observed buggy behavior, it's just undefined behavior
according to the spec. This warning can be enabled with
-Wshift-sign-overflow.

Original patch by Oleg Slezberg, with style tweaks and some correctness
fixes by me.

llvm-svn: 126342

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/test/Analysis/retain-release-gc-only.m b/clang/test/Analysis/retain-release-gc-only.m
index 6f1dd92df99..7d7c58fbcd5 100644
--- a/clang/test/Analysis/retain-release-gc-only.m
+++ b/clang/test/Analysis/retain-release-gc-only.m
@@ -189,7 +189,7 @@ CVTimeStamp;
 }
 typedef int CIFormat;
 @end  enum {
-kDAReturnSuccess = 0,     kDAReturnError = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x01,     kDAReturnBusy = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x02,     kDAReturnBadArgument = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x03,     kDAReturnExclusiveAccess = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x04,     kDAReturnNoResources = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x05,     kDAReturnNotFound = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x06,     kDAReturnNotMounted = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x07,     kDAReturnNotPermitted = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x08,     kDAReturnNotPrivileged = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x09,     kDAReturnNotReady = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x0A,     kDAReturnNotWritable = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x0B,     kDAReturnUnsupported = (((0x3e)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x0C };
+kDAReturnSuccess = 0,     kDAReturnError = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x01,     kDAReturnBusy = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x02,     kDAReturnBadArgument = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x03,     kDAReturnExclusiveAccess = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x04,     kDAReturnNoResources = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x05,     kDAReturnNotFound = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x06,     kDAReturnNotMounted = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x07,     kDAReturnNotPermitted = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x08,     kDAReturnNotPrivileged = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x09,     kDAReturnNotReady = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x0A,     kDAReturnNotWritable = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x0B,     kDAReturnUnsupported = (((0x3eU)&0x3f)<<26) | (((0x368)&0xfff)<<14) | 0x0C };
 typedef mach_error_t DAReturn;
 typedef const struct __DADissenter * DADissenterRef;
 extern DADissenterRef DADissenterCreate( CFAllocatorRef allocator, DAReturn status, CFStringRef string );