[LLVMbugs] [Bug 19938] New: Strange false positive with address sanitizer

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=19938

            Bug ID: 19938
           Summary: Strange false positive with address sanitizer
           Product: clang
           Version: 3.4
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: sstewartgallus00 at mylangara.bc.ca
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 12601
  --> http://llvm.org/bugs/attachment.cgi?id=12601&action=edit
A very strange testcase that gives a false positive

So this might be some bug with X11 or GLibc but anyways attached is a very
strange case that generates a false positive for address sanitizer.
I really wish I could reduce this testcase past using X11.
Annoyingly, Valgrind doesn't seem to complain so there's not an obvious error.

To build it compile as clang -g -fsanitize=address-full clang-sanitizer.c -lX11
-pthread

Some system information:

> uname -a
Linux alonzo 3.13.0-24-generic #1trisquel1 SMP Tue May 13 15:17:50 UTC 2014
x86_64 x86_64 x86_64 GNU/Linux

> /lib/x86_64-linux-gnu/libc.so.6
GNU C Library (Ubuntu EGLIBC 2.15-0ubuntu10.5) stable release version 2.15, by
Roland McGrath et al.
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.6.3.
Compiled on a Linux 3.2.50 system on 2013-09-30.
Available extensions:
    crypt add-on version 2.1 by Michael Glad and others
    GNU Libidn by Simon Josefsson
    Native POSIX Threads Library by Ulrich Drepper et al
    BIND-8.2.3-T5B
libc ABIs: UNIQUE IFUNC
For bug reporting instructions, please see:
<http://www.debian.org/Bugs/>.

The version of X11 is 2:1.4.99.1-0ub.

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