[Bug c++/17112] New: default operator= for struct with packed bitfield is wrong

["gene at digilicious dot com" <gcc-bugzilla@gcc.gnu.org>]

#include <iostream>
                                                                               
                                                              
using namespace std;
 
struct myint24 {
  int int24:24  __attribute__ ((packed)); 
};
 
myint24 x[3] = {
  0x123456,
  0x789abc,
  0xdef012
};
 
myint24 y[3];            // starts out as zeros
 
int main(int ac, char* av[])
{
  y[1] = x[1];           // should only copy 3 bytes
  for ( int i=0; i<3; ++i )
    if ( 0 != y[i].int24 )
      cout << i << endl; // should only find one non-zero element, and print "1"
  return 0;
}

// compile with default options

// the output should be "1" but it's not

// the bug exists in 3.4.1 and 3.5.0 cvs snapshot from 20040818
// also in 3.3 versions, but not in 3.2

// I don't expect you need the preprocessed sources in this case, since
// the example is so small.

-- 
           Summary: default operator= for struct with packed bitfield is
                    wrong
           Product: gcc
           Version: 3.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: gene at digilicious dot com
                CC: gcc-bugs at gcc dot gnu dot org,gene at digilicious dot
                    com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17112