[Bug c++/11752] partial ordering overloaded function templates

["bangerth at dealii dot org" <gcc-bugzilla@gcc.gnu.org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11752



------- Additional Comments From bangerth at dealii dot org  2003-08-05 16:32 -------
Here's a self-contained testcase:
-----------------------------
template <typename> struct X {};

template<int shift, typename T>  T    f (T);
template<int shift, typename T>  X<T> f (X<T>);

int main () {
  X<int> x;
  f<6> (x);
}
------------------------------

It fails with 3.4 and icc7:
g/x> /home/bangerth/bin/gcc-3.4-pre/bin/c++ -c bug.cc
bug.cc: In function `int main()':
bug.cc:8: error: call of overloaded `f(X<int>&)' is ambiguous
bug.cc:3: note: candidates are: T f(T) [with int shift = 6, T = X<int>]
bug.cc:4: note:                 X<T> f(X<T>) [with int shift = 6, T = int]
g/x>
g/x> icc -c bug.cc
bug.cc(8): error: more than one instance of overloaded function "f" matches the
argument list:
            function template "f<shift,T>(T)"
            function template "f<shift,T>(X<T>)"
            argument types are: (X<int>)
    f<6> (x);
    ^

compilation aborted for bug.cc (code 2)

I recall that we had another PR like this, where the existence of the
first template arg made a difference, and I remember I didn't understand
the reasoning why that was deemed illegal. Note that if the int template
arg is removed (along with the <6> on the call of f), then both
compilers grok the code.

Someone with more knowledge will have to look at this.

W.