Why code using local struct as parameter for STL function does not compile in g++?

Question

I have such code which works well:

#include 
#include 

char x[11]= \"ABCDEFGHIJ\";
char y[11];

struct F {
    char operator ()         


        

Answer 1

In C++-98/03 the second code is not valid, since F is a local type; in facts, at §14.3.1.2 it's stated that

A local type, a type with no linkage, an unnamed type or a type compounded from any of these types shall not be used as a template-argument for a template type-parameter.

[Example:

template  class X { /* ... */ };
void f()
{
    struct S { /* ... */ };
    X x3;         // error: local type used as template-argument
    X x4;        // error: pointer to local type used as template-argument
}

—end example] [Note: a template type argument may be an incomplete type (3.9). ]

In C++-0x this limitation is removed; in the same section, the new standard draft (N3126) explicitly shows this in the example:

[ Example:

template  class X { };
template  void f(T t) { }
struct { } unnamed_obj;

void f() {
    struct A { };
    enum { e1 };
    typedef struct { } B;
    B b;
    X x1;             // OK
    X x2;            // OK
    X x3;             // OK
    f(e1);               // OK
    f(unnamed_obj);      // OK
    f(b);                // OK
}

— end example ] [ Note: a template type argument may be an incomplete type (3.9). — end note ]