Why Does Template Member Function Invocation Within a Template Function Fail in C ?

Template Member Function Invocation within Template Function

In the given code, an attempt to invoke a template member function f within a template function g fails with compilation errors:

<code class="cpp">template<class X> struct A {
   template<int I> void f() {}
};

template<class T> void g()
{
   A<T> a;
   a.f<3>();  // Compilation fails here (Line 18)
}</code>

According to the C Standard (14.2/4), when a member template specialization is called after a ., the template keyword must be explicitly specified to differentiate it from a non-template member function.

To resolve the compilation error, the code should be modified as follows:

<code class="cpp">template<class T> void g()
{
   A<T> a;
   a.template f<3>();  // add `template` keyword here
}</code>

By adding the template keyword, the compiler recognizes that the invoked function is a member template specialization, resolving the ambiguity and allowing the code to compile successfully.

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