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[Bug c++/49949] wrong sign for product of complex<double> and double with -O2
- From: "hjl.tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Wed, 28 Sep 2011 15:54:09 +0000
- Subject: [Bug c++/49949] wrong sign for product of complex<double> and double with -O2
- Auto-submitted: auto-generated
- References: <bug-49949-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49949
--- Comment #8 from H.J. Lu <hjl.tools at gmail dot com> 2011-09-28 15:54:09 UTC ---
(In reply to comment #0)
> With the -O2 flag and in a very specialized circumstance, the product of a
> complex<double> and a double has the wrong sign.
>
> The problem arises when the blitz++ array library is used.
> (http://www.oonumerics.org/blitz/) Unfortunately, I could not prune out all the
> references to the unnecessary C++ standard libraries. The size of the .ii file
> is therefore pretty big. I hope the report will still be useful.
>
> The output of the executable gcc_complex_bug should be
>
> (-0.0,-1.0)x100.0=(0.0,100.0)
>
I also got
(-0.0,-1.0)x100.0=(-0.0,-100.0)
with GCC 4.7.0 revision 179164. Why should we get (0.0,100.0)?