[Bug c++/21089] New: c++ accepts invalid static const double members with initializer

["matz at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

See this testcase: 
------------------------- 
struct Ball { 
    static const double diameter = 20; 
    void setPosition(double ,double ); 
    double vect_Pos; 
}; 
 
void move (double, double); 
 
void Ball::setPosition(double xval,double yval) { 
    vect_Pos=xval; 
    move(xval-(diameter/2),yval-(diameter/2)); 
} 
------------------------- 
 
This is from kbilliard, and I only noticed the problem, because a reference 
to Ball::diameter is left in the generated code, which can't be resolved, 
as it's defined nowhere.  Initially I was tricked by the java like syntax, 
but then saw PR20098, according to which this is invalid code (for two 
reasons).  So it seems there are two problems: 
  1) missed optimization, as for instance if I remove the 'vectPos=xval' line 
     I get no linker error, and in fact in the dumps the references to 
     diameter are substituted by the defined value (double)20 
  2) the invalidness of the code is not diagnosed. 
 
It's invalid for two reasons I think, first the missing definition, instead 
of the declaration.  But that can't be diagnosed except by the linker, which 
indeed it does. 
 
But when reading PR20098 I learned that static const members are only  
allowed to have an initializer when they are of integral type.  This is 
not the case here.  If the compiler would have diagnosed it, the root cause 
of this problem had been more visible.

-- 
           Summary: c++ accepts invalid static const double members with
                    initializer
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: matz at suse dot de
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21089