statics / enums still broken - any fix in sight?

[Markus Werle]

Hi!

I still encounter (severe) problems with compile time constants,
even in today's cvs:

g++ (GCC) 3.4 20030520 (experimental)

Both code pieces compile fine with Intel-7.0 and option -ansi,
so they either are gcc bugs or the grey zone of the standard.

Please (!) tell me whether there are fixes in sight for this or
whether I have to take the tedious task to put workarounds
everywhere in my code.

Since it stresses compiler's template section at maximum
I propose the daixtrose lib (http://daixtrose.sf.net)
as a benchmark for g++. Try to compile this and then fix things 
like those below (or sue me for not writing compliant code ;-)):

---------------------------------------------------------------
#include <iostream>

template<class T> 
class has_member_disambiguation // Thanks to Paul Mensonides
{
protected:
  template<class U> static char check(typename U::Disambiguation*);
  template<class U> static char (& check(...))[2];

public:
  enum { value = (sizeof(check<T>(0)) == 1) };
};

struct A 
{
  typedef double Disambiguation;
};

struct B {};


int main()
{
  std::cerr << has_member_disambiguation<A>::value << std::endl;
  std::cerr << has_member_disambiguation<B>::value << std::endl;
}
------------------------------------------------------------------

GCC-3.4-Bugs.C: In instantiation of `has_member_disambiguation<A>':
GCC-3.4-Bugs.C:24:   instantiated from here
GCC-3.4-Bugs.C:11: error: invalid use of 
   undefined type `class has_member_disambiguation<A>'
GCC-3.4-Bugs.C:5: error: declaration of `
   class has_member_disambiguation<A>'
GCC-3.4-Bugs.C:11: error: enumerator 
   value for `value' not integer constant
GCC-3.4-Bugs.C: In instantiation of `has_member_disambiguation<B>':
GCC-3.4-Bugs.C:25:   instantiated from here
GCC-3.4-Bugs.C:11: error: invalid use of 
   undefined type `class has_member_disambiguation<B>'
GCC-3.4-Bugs.C:5: error: declaration of `
   class has_member_disambiguation<B>'
GCC-3.4-Bugs.C:11: error: enumerator 
   value for `value' not integer constant


The next one I think I maybe already reported, but anyway,
it _should_ work, but does not:

--------------------------------------------------------
template <class T1, class T2> 
struct Is { static const bool SameType = false; };

template <class T> 
struct Is<T, T> { static const bool SameType = true; };

#define SAME_TYPE(T1, T2) Is<T1, T2>::SameType 


template <class T>
struct Test
{
  static const bool test1 = SAME_TYPE(double, T);
  static const bool test2 = false;

  static const bool result = test1 || test2;
};


int main() {
  Test<double> T1;
}
---------------------------------------------------------

g++ ~/hp-home/C++/EXPERIMENTAL/GCC-3.4-CannotAppearInConstantExpr.C
/home/markus/hp-home/C++/EXPERIMENTAL/GCC-3.4-CannotAppearInConstantExpr.C:16: 
error: `
   Test<T>::test1' cannot appear in a constant-expression


IMHO it can.


best regards,


Markus


-- 

Compile time analytic differentiation? 
Yes, at http://daixtrose.sourceforge.net/