[Bug c++/17232] New: classes and class template specializations treated differently w.r.t. core issue #337

[cludwig at cdc dot informatik dot tu-darmstadt dot de]

cludwig@lap200:~/C++/gcc3.4/tmp> LC_ALL=C g++ -v 
Reading specs from /opt/gcc/gcc-3.4.1/lib/gcc/i686-pc-linux-gnu/3.4.1/specs 
Configured with: ../gcc-3.4.1/configure --prefix=/opt/gcc/gcc-3.4.1 
--enable-threads=posix --enable-version-specific-runtime-libs 
--enable-languages=c,c++ --enable-__cxa_atexit --enable-c-mbchar 
--enable-concept-checks --enable-libstdcxx-debug --enable-c99 
--enable-libstdcxx-pch 
Thread model: posix 
gcc version 3.4.1 
 
cludwig@lap200:~/C++/gcc3.4/tmp> cat ./is_abstract_test.cc 
template<typename T> 
class A { 
  virtual void f() = 0; 
}; 
 
class B { 
  virtual void f() = 0; 
}; 
 
template<typename T> 
int g(T (*)[1]) { 
  return 0; 
} 
 
template<typename T> 
int g(...) { 
  return 1; 
} 
 
int main() { 
  return  (g< A<int> >(0) == g< B >(0)) ; 
} 
 
cludwig@lap200:~/C++/gcc3.4/tmp> ./is_abstract_test ; echo $? 
0 
 
According to http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/cwg_defects.html#337, 
type deduction fails if it implies constructing an array of an abstract class. 
(This enables traits like boost::is_abstract<T>::value.) Therefore, above 
program is supposed to choose for both g< A<int> >() and g<B>() the second 
overload (the one that returns 1), whence the program's return value should be 
non-zero. 
 
However, g++ 3.4.1 chooses the first overload for g< A<int> >(). 
 
Regards 
 
Christoph

-- 
           Summary: classes and class template specializations treated
                    differently w.r.t. core issue #337
           Product: gcc
           Version: 3.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: cludwig at cdc dot informatik dot tu-darmstadt dot de
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17232