http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54755
Bug #: 54755
Summary: Template instantiation confused by actual template
argument definitions before and after template
definition
Classification: Unclassified
Product: gcc
Version: 4.6.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: [email protected]
ReportedBy: [email protected]
The following code:-
// ---------------------------------------------
#include <iostream>
// Before
void Function ( int ) { std::cout << "int\n"; }
void Function ( long ) { std::cout << "long\n"; }
template <class x>
struct TemplateClass
{
x Variable;
void MemberFunction() { Function(Variable); }
};
// After
void Function ( float ) { std::cout << "float\n"; }
int main ( int, char** ) {
TemplateClass<int> I;
I.MemberFunction();
TemplateClass<long> L;
L.MemberFunction();
TemplateClass<float> F;
F.MemberFunction();
}
// ---------------------------------------------
gives the compiler error:- error: call of overloaded 'Function(float&)' is
ambiguous
However, if all definitions of Function are in the "Before" block, and none in
"After" it works.
If all definitions are in the "After" block, and none in the "Before" code, it
also works.
If the int version of Function is in the "Before" code and the others in
"After" all instantiations of the template use the int version because of
implicit type conversion.
This looks like a bug in the symbol lookup. All overloaded versions of Function
can be found if they are either before or after the definition of the template
that happens to use them, but only if they are all defined together. Separate
the definitions before and after the template definition and it goes wrong.
Note: iostream output has only been used in the example to illustrate the bug
using std output. The code can be further simplified by removing iostream and
the same thing happens.
