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Date: Thu, 04 May 2006 10:47:00 -0000
Subject: [Bug other/27417]  New: wrong code or aliasing violation with missed diagnostic?
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From: "pluto at agmk dot net" <gcc-bugzilla@gcc.gnu.org>
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inline float quickBinaryToFloat( unsigned const& in )
{
        return reinterpret_cast< float const& >( in ) ;
}

float foo( unsigned x )
{
        unsigned y = ( x * 2 ) + 1;
        return quickBinaryToFloat( y );
}


[ wrong-code generated ]

$ i486-gnu-linux-g++ bin2float.cpp -Wall -O2 -c -fomit-frame-pointer -m32

00000000 <foo(unsigned int)>:
   0:   83 ec 10                sub    $0x10,%esp
   3:   d9 44 24 0c             flds   0xc(%esp)
   7:   83 c4 10                add    $0x10,%esp
   a:   c3                      ret

[ correct code generated ]

$ i486-gnu-linux-g++ bin2float.cpp -Wall -O2 -c -fomit-frame-pointer -m32 \
                                   -fno-strict-aliasing

00000000 <foo(unsigned int)>:
   0:   83 ec 10                sub    $0x10,%esp
   3:   8b 44 24 14             mov    0x14(%esp),%eax
   7:   8d 44 00 01             lea    0x1(%eax,%eax,1),%eax
   b:   89 44 24 0c             mov    %eax,0xc(%esp)
   f:   d9 44 24 0c             flds   0xc(%esp)
  13:   83 c4 10                add    $0x10,%esp
  16:   c3                      ret


-- 
           Summary: wrong code or aliasing violation with missed diagnostic?
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pluto at agmk dot net
 GCC build triplet: i486-linux
  GCC host triplet: i486-linux
GCC target triplet: i486-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27417