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* [Bug c++/21756] New: inconsistent result of left shift
@ 2005-05-25 19:33 wb at fnal dot gov
  2005-05-25 19:52 ` [Bug c++/21756] " pinskia at gcc dot gnu dot org
  0 siblings, 1 reply; 2+ messages in thread
From: wb at fnal dot gov @ 2005-05-25 19:33 UTC (permalink / raw)
  To: gcc-bugs

Reading specs from /usr/local/lib/gcc/i686-pc-cygwin/3.4.4/specs
Configured with: ../configure --enable-languages=c,c++
Thread model: single
gcc version 3.4.4

// -------------------------
// evaluate 1 << 32 in two different ways,
// obtaining different results

#include <iostream>

int main()
{
  unsigned long k = 32UL;
  unsigned long r1 = ( 1UL << k );  // incorrectly evaluated per 5.8/2
    std::cout << "r1 = " << r1 << "\n";  // emits "r1 = 1"

  unsigned long r2 = ( 1UL << 32UL );  // warns, but correctly evaluated
    std::cout << "r2 = " << r2 << "\n";  // emits "r2 = 0"

  return 0;
}

-- 
           Summary: inconsistent result of left shift
           Product: gcc
           Version: 3.4.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: wb at fnal dot gov
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21756


^ permalink raw reply	[flat|nested] 2+ messages in thread
* [Bug c++/21756] inconsistent result of left shift
  2005-05-25 19:33 [Bug c++/21756] New: inconsistent result of left shift wb at fnal dot gov
@ 2005-05-25 19:52 ` pinskia at gcc dot gnu dot org
  0 siblings, 0 replies; 2+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-05-25 19:52 UTC (permalink / raw)
  To: gcc-bugs


------- Additional Comments From pinskia at gcc dot gnu dot org  2005-05-25 19:34 -------
This is undefined as per 5.8/1:
"The behavior is undefined if the right operand is negative, or greater than or equal to the length in 
bigs of the promoted left operand".

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21756


^ permalink raw reply	[flat|nested] 2+ messages in thread
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2005-05-25 19:33 [Bug c++/21756] New: inconsistent result of left shift wb at fnal dot gov
2005-05-25 19:52 ` [Bug c++/21756] " pinskia at gcc dot gnu dot org

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