[Bug c/67570] New: comparison rules fails

[ka_bena at yahoo dot fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67570

            Bug ID: 67570
           Summary: comparison rules fails
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ka_bena at yahoo dot fr
  Target Milestone: ---

#include <stdio.h>

 int main(void)
{ 
   int         pos        ;
   int         pos1       ;
   int         pos2       ;
   long double A    = 0.L ;

   union { 
           long double X                 ; 
           char unsigned mask[sizeof(A)] ; 
         } alfa ;

   alfa.X = A                    ;
   pos    = 32                   ;
   pos1   = 11 - ( pos - 1 ) / 8 ;
   pos2   = 8                    ;

   alfa.mask[pos1] =((char unsigned )1 << (sizeof(char unsigned) * 8 - pos2)) ^
alfa.mask[pos1] ;

   printf ( "   [alfa.X]        = %LE \n" , alfa.X        ) ; 
   printf ( "   [alfa.X == 0.L] = %i  \n" , alfa.X == 0.L ) ; 
   printf ( "   [alfa.X != 0.L] = %i  \n" , alfa.X != 0.L ) ; 
   printf ( "   [alfa.X <= 0.L] = %i  \n" , alfa.X <= 0.L ) ;   
   printf ( "   [alfa.X >= 0.L] = %i  \n" , alfa.X >= 0.L ) ;   
   printf ( "   [alfa.X <  0.L] = %i  \n" , alfa.X <  0.L ) ;   
   printf ( "   [alfa.X >  0.L] = %i  \n" , alfa.X >  0.L ) ;   

   return 0 ;

}

/*

   Results:
   [alfa.X]        = 0.000000E+000                                              
   [alfa.X == 0.L] = 0                                                          
   [alfa.X != 0.L] = 1                                                          
   [alfa.X <= 0.L] = 0                                                          
   [alfa.X >= 0.L] = 0                                                          
   [alfa.X <  0.L] = 0                                                          
   [alfa.X >  0.L] = 0 

   Note:
   Binary representation IEEE 754 of alfa.X is:
   0000000000000000 0 000000000000001
0000000000000000000000000000000000000000000000000000000000000000
   It seems that comparison rules fails in this case.

   Microsoft Windows XP Profesional version2002 Service Pack 3.
   Gcc 4.8.0 win32 mingw32 -std=C99 

*/