[Bug c++/9436] [ABI] passing a class template followed by a template value of this class

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

------- Comment #7 from reichelt at gcc dot gnu dot org  2005-11-17 15:23 -------
Giovanni's example now compiles on mainline and the 4.0 branch
due to Mark's patch for PR 23789:

==================================================
template <typename T, int I = int()> struct A {};

template <typename T> void foo(A<T>) {}

void bar()
{
    foo(A<char>());
}
==================================================

However, I still get "sorry, unimplemented" for the following testcase
which is closer to the original one:

==================================================
template <typename T, T I = T()> struct A {};

template <typename T> void foo(A<T>) {}

void bar()
{
    foo(A<char>());
}
==================================================

bug.cc: In function 'void foo(A<T, T()>) [with T = char]':
bug.cc:3: sorry, unimplemented: zero-operand casts cannot be mangled due to a
defect in the C++ ABI

Note that "T()" is not a cast, but a default-constructed object.


A related problem is shown by the following testcase:

==================================================
template<int> struct A {};

A<int()> a;
==================================================

bug.cc:3: error: type/value mismatch at argument 1 in template parameter list
for `template<int <anonymous> > struct A'
bug.cc:3: error:   expected a constant of type `int', got `int ()()'
bug.cc:3: error: invalid type in declaration before ';' token

Obviously "int()" is not interpreted as "0", but as a function "int ()()".
Maybe "T()" in the example above causes the same problems.

Btw, icc compiles all testcases without problems.


-- 

reichelt at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at codesourcery dot com
           Keywords|ice-on-valid-code           |rejects-valid


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=9436