[Bug c/13793] New: On 64 bit, casting neg value to unsigned long gives incorrect result

[larue at cadence dot com]

Take this simple C program
#include <stdio.h>
int main(int argc, char** argv)
{
   double dummy = -5;
   printf("The following lines should match:\n");
   printf("double dummy = -5; (unsigned long) (dummy) = %lu \n", (unsigned 
long) dummy);
   printf("(unsigned long) (-5.0)                     = %lu \n", (unsigned 
long) (-5.0));
}

gcc -m64 gcc64bitIntegerConversionBug.c
humdinger{ larue 187}:a.out
The following lines should match:
double dummy = -5; (unsigned long) (dummy) = 9223372036854775807 
(unsigned long) (-5.0)                     = 18446744073709551611 

If we don't use -m64 we get the right answers
humdinger{ larue 153}:a.out
The following lines should match:
double dummy = -5; (unsigned long) (dummy) = 4294967291 
(unsigned long) (-5.0)                     = 4294967291 


Here are the results using the Solaris native compiler:
humdinger{ larue 154}: cc -xarch=v9 gcc64bitIntegerConversionBug.c
"gcc64bitIntegerConversionBug.c", line 7: warning: conversion of double to 
integral is out of range
humdinger{ larue 155}:a.out
The following lines should match:
double dummy = -5; (unsigned long) (dummy) = 18446744073709551611 
(unsigned long) (-5.0)                     = 18446744073709551611 

Here are the specifics on my environment:

humdinger{ larue 139}:uname -a
SunOS humdinger 5.7 Generic_106541-23 sun4u sparc SUNW,Ultra-4
humdinger{ larue 140}:g++ -v
Reading specs from /dv/tools/3rdParty/gcc/3.2/bin/../lib/gcc-lib/sparc-sun-
solaris2.7/3.2/specs
Configured with: ../configure --prefix= --enable-shared=libgcc,libstdc++ --
enable-threads --enable-languages=c,c++
Thread model: posix
gcc version 3.2

-- 
           Summary: On 64 bit, casting neg value to unsigned long gives
                    incorrect result
           Product: gcc
           Version: 3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: larue at cadence dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13793