[Bug c++/19317] New: forgets to deep-copy temporary return value

["mueller at kde dot org" <gcc-bugzilla at gcc dot gnu dot org>]

Mark Mitchel's commit to fix PR c++/16405 introduced a miscompilation 
in Qt. It took me a few weeks to deduce a testcase. testcase is: 
 
=== Cut === 
extern "C" void abort( void ); 
 
struct A 
{ 
    A() { d = d2 = 0; width = -1; } 
    A( int _w ) : d( 0 ), d2( 0 ), width( _w ) {} 
 
    A  b( const A &r ) const; 
    int d; 
    int d2; 
    int width; 
}; 
 
A A::b( const A &r ) const 
{ 
    A tmp; 
    tmp.width = width < r.width ? width : r.width; 
    return tmp; 
} 
 
int main() 
{ 
        A a( 100 ); 
        a = a.b( A( 10 ) ); 
        if ( a.width != 10 ) 
               abort(); 
} 
=== Cut === 
 
The issue is that the result of "a.b(A (10))" is never copied to a, hence 
the if() afterwards fails.

-- 
           Summary: forgets to deep-copy temporary return value
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mueller at kde dot org
                CC: gcc-bugs at gcc dot gnu dot org,mark at codesourcery 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=19317