Re: bug in gcc (GCC) 4.0.1 20050727 (Red Hat 4.0.1-5)

[Mark Frazer <mark at mjfrazer dot org>]

Mark Frazer <mark@mjfrazer.org> [05/08/02 09:32]:
> Richard Guenther <richard.guenther@gmail.com> [05/08/02 09:29]:
> > Try -fno-strict-aliasing.  This may be related to PR23192.
> 
> -fno-strict-aliasing does indeed make the problem go away.

changing the de-serialization function to:

      double parse_double(uint &offset, vector<uint8> const &bytecode)
         throw (std::invalid_argument)
      {
         union {
            uint64 ival;
            double dval;
         } rtn;
         rtn.ival  = uint64(next_byte(offset, bytecode)) << 56;
         rtn.ival |= uint64(next_byte(offset, bytecode)) << 48;
         rtn.ival |= uint64(next_byte(offset, bytecode)) << 40;
         rtn.ival |= uint64(next_byte(offset, bytecode)) << 32;
         rtn.ival |= uint64(next_byte(offset, bytecode)) << 24;
         rtn.ival |= uint64(next_byte(offset, bytecode)) << 16;
         rtn.ival |= uint64(next_byte(offset, bytecode)) << 8;
         rtn.ival |= uint64(next_byte(offset, bytecode));
         return rtn.dval;
      }

Allows for the strict-aliasing optimization to be left in.  So, it seems
the bug was mine, not gcc's.

I'm off to search for other reinterpret_cast abuses in my code...

cheers
-mark
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