Bug#673749: g++-4.7: gcc47 generates buggy code with optimisation flags
 

Package: g++-4.7
Version: 4.7.0-8
Severity: normal
Tags: upstream

Dear Maintainer,

* What led up to the situation?
I ported feel++ to gcc47 and found out that it generates buggy code(generating
segfault) in optimisation mode.
Here are the steps to reproduce it
- install feel++-apps
- execute feel_doc_myfunctionspace (compiled using CMAKE_BUILD_TYPE=Release)
- it generates a segfault

what happens is that a data structure containing only a double data member seem
to be optimized away and became dangling reference (invalid read using
valgrind).
The code crashes at line 220 of doc/manual/tutorial/myfunctionspace.cpp when
evaluating the expression template data structure g defined on line 215.

- in gcc47 with CMAKE_BUILD_TYPE=Debug, it works without problems
- with gcc45, gcc46, clang31 on Linux and OSX there are no problems at all
in RelWithDebInfo and Release mode (CMAKE_BUILD_TYPE)

Hence I believe that this is a bug in gcc47 code generation/optimisation.



-- System Information:
Debian Release: wheezy/sid
APT prefers unstable
APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.2.0-2-amd64 (SMP w/1 CPU core)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages g++-4.7 depends on:
ii gcc-4.7 4.7.0-8
ii gcc-4.7-base 4.7.0-8
ii libc6 2.13-32
ii libgmp10 2:5.0.5+dfsg-1.1
ii libmpc2 0.9-4
ii libmpfr4 3.1.0-5
ii libstdc++6-4.7-dev 4.7.0-8
ii zlib1g 1:1.2.7.dfsg-2

g++-4.7 recommends no packages.

Versions of packages g++-4.7 suggests:
pn g++-4.7-multilib <none>
pn gcc-4.7-doc <none>
pn libstdc++6-4.7-dbg <none>

-- no debconf information



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