[Bug tree-optimization/59970] Bogus warnings at low optimization levels

[matt at godbolt dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59970

Matt Godbolt <matt at godbolt dot org> changed:

           What    |Removed                     |Added
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                 CC|                            |matt at godbolt dot org

--- Comment #2 from Matt Godbolt <matt at godbolt dot org> ---
FWIW I stumbled over what I believe is the same issue inside the boost v1.55.0
lexical_cast implementation.  That also only shows up as a "possible
uninitialized" at -Og optimization only.  I can provide preprocessed source if
necessary (though, being boost, it's 80k lines, ugh) but if you have gcc4.9.0
and boost 1.55 available:

$ cat test.cc
#include <boost/lexical_cast.hpp>

int test() { return boost::lexical_cast<int>("1"); }

$ g++ -Wall -Wextra -Og -c test.cc
test.cc: In function ‘int test()’:
test.cc:4:40: warning: ‘result’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
     return boost::lexical_cast<int>("1");


The relevant lines in boost itself appear to be
http://svn.boost.org/svn/boost/tags/release/Boost_1_55_0/boost/lexical_cast.hpp
lines 2365-2377 where the "result" is optionally initialized.

I'll also submit this to the boost developers in case they have some ideas.