False positive: "Undefined or garbage value returned to caller"

[llvmbot]

Bugzilla Link	18309
Resolution	DUPLICATE
Resolved on	Dec 23, 2013 12:40
Version	trunk
OS	Linux
Attachments	Simple test case
Reporter	LLVM Bugzilla Contributor
CC	@belkadan

Extended Description

Using:
clang version 3.5 (trunk 197863)
Target: x86_64-unknown-linux-gnu
Thread model: posix

I'm getting a false positive "Undefined or garbage value returned to caller" for a variable which is guaranteed to be written to in one of the 'case' entries of a 'switch' statement.

Test case attached. Note, that false positive is not given for a switch() on enum values, but it is given for switch() on an int where two bits are masked out.

Use: scan-build --use-analyzer <...>/bin/clang gcc -std=c99 -o test.o -c test.c

[llvmbot]

assigned to @tkremenek

[belkadan]

I'm going to call this a duplicate of bug #13399 . We don't currently reason about bitwise constraints, but we could consider adding a special case if it's the low bits that are being masked, because that can be represented as an integral range.

*** This bug has been marked as a duplicate of bug #13399 ***