[Bug c++/55513] [4.7/4.8 Regression] Incorrect snprintf folding when building with -std=c++0x

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55513

--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> 2012-12-07 05:21:01 UTC ---
(In reply to comment #8)
>                    /* Allow any built-in function; if the expansion
>                       isn't constant, we'll deal with that then.  */
>                    && !is_builtin_fn (fun))

The problem seems to be in the dealing with it "then";
cxx_eval_builtin_function_call needs to actually check whether folding the call
produces a constant or not.