[Bug middle-end/50066] [4.7 Regression] Bad signed int to unsigned long long conversion

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50066

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
   Last reconfirmed|                            |2011-11-30
         Resolution|INVALID                     |
     Ever Confirmed|0                           |1

--- Comment #17 from H.J. Lu <hjl.tools at gmail dot com> 2011-11-30 20:52:59 UTC ---
(In reply to comment #6)
> On Sat, 13 Aug 2011, hjl.tools at gmail dot com wrote:
> 
> > --- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> 2011-08-13 12:09:16 UTC ---
> > This code comes from mpz/set_si.c in gmp:
> > 
> > void
> > mpz_set_si (mpz_ptr dest, signed long int val)
> > {
> >   mp_size_t size;
> >   mp_limb_t vl;
> > 
> >   vl = (mp_limb_t) (unsigned long int) (val >= 0 ? val : -val);
> 
> So that GMP code is buggy.  Change it to
> 
> vl = (mp_limb_t) (val >= 0 ? (unsigned long int) val : -(unsigned long int)
> val);
> 
> and it will be valid.

It doesn't work:

[hjl@gnu-6 tmp]$ cat x.c
#include <stdio.h>
#include <limits.h>

unsigned long long
__attribute__ ((noinline))
foo (signed int v_digit)
{
  unsigned long long x;

  x = (unsigned long long) (v_digit >= 0 ? (unsigned int) v_digit : (unsigned
int) -v_digit);
  return x;
}

int
main ()
{
  unsigned long long x;

  x = foo (INT_MIN);
  printf ("%lld\n", x);
  x = foo (INT_MAX);
  printf ("%lld\n", x);
  return 0;
}
[hjl@gnu-6 tmp]$ /export/build/gnu/gcc-x32/release/usr/gcc-4.7.0-x32/bin/gcc
-O2 x.c
[hjl@gnu-6 tmp]$ ./a.out 
-2147483648
2147483647
[hjl@gnu-6 tmp]$ /export/build/gnu/gcc-x32/release/usr/gcc-4.7.0-x32/bin/gcc -O
x.c
[hjl@gnu-6 tmp]$ ./a.out 
2147483648
2147483647
[hjl@gnu-6 tmp]$