Re: Dependent Template Issue? g++ gives the following ==> error: expected primary-expression before "int"

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Thu, 12 Jul 2007 15:49:36 -0400
Message-ID:
<f760kg$532$1@news.datemas.de>
Lawrence Spector wrote:

I ran into a problem using g++. Visual Studio 2005 never complained
about this, but with g++ I ran into this error. I can't figure out if
I've done something wrong or if this is a compiler bug. Here's a very
simple example which should illustrate what I'm doing.

#include <iostream>

template <class T>
class TestBase
{
public:
TestBase() {}

int testMethod()
{
return T::callMethod<int>(); // ERROR?


Add the keyword template:

   return T::template callMethod<int>();

Also, it is most likely that it's not going to work since
even if 'callMethod' is a member of 'T', you would need
an instance of 'T' to call non-static member function. If
you hope to use 'this' here, it shouldn't work because
there is no convestion from 'this' (which is of the type
'TestBase<T>' to 'T').

}
};

class Derived : public TestBase<Derived>
{
public:
Derived() : TestBase<Derived>() {}

template <class T>
T callMethod()
{
return T();
}
};

int main()
{
Derived derived;

int x = derived.callMethod<int>();
int y = derived.testMethod(); // CALLED FROM HERE

return 0;
}

Results in the following:

$ g++ -c GccTemplateCompile.cpp
GccTemplateCompile.cpp: In member function `int
TestBase<T>::testMethod()':
GccTemplateCompile.cpp:12: error: expected primary-expression before
"int"
GccTemplateCompile.cpp:12: error: expected `;' before "int"
GccTemplateCompile.cpp:12: error: expected primary-expression before
"int"
GccTemplateCompile.cpp:12: error: expected `;' before "int"

Does anyone have any idea what's going on?


The compiler does not know that 'callMethod' is a template member.

V
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