[RESOLVED] Why g++ fails to find correct overload in this case?

[ar115]

Hi,
when I want to compile the below i get an error like
no matching function for call to ...
from g++

#include <iostream>
#include <fstream>
#include <vector>

template< class T >
inline void
write_binary( const T& _t, std::ofstream& out )
{
	out.write( (char*)(&_t), sizeof(T) );
}

struct foo {
int n;
void write_binary( std::ofstream& f ) const;
};

void foo::write_binary( std::ofstream& f ) const
{
write_binary( n, f );
}

int main(){
foo f;
std::ofstream ofile("file.tss");
f.write_binary( ofile );
}

[Joeman]

I suppose you need to use the scope operator

[ar115]

but the signatures of foo::write_binary and global write_binary are different
so the compiler must be able to choose correct function
but it erros

test.cpp: In member function ‘void foo::write_binary(std::ofstream&) const’:
test.cpp:20: error: no matching function for call to ‘foo::write_binary(constint&,std::basic_ofstream<char,std::char_traits<char> >&) const’
test.cpp:18: note: candidates are: void foo::write_binary(std::ofstream&) const

[code_carnage]

Use this...

::write_binary( n, f );

[code_carnage]

Compilar is looking for a overload in the class, which it does not finds.
and errors out..Because you can not over load a member function with a global function..

[superbonzo]

but the signatures of foo::write_binary and global write_binary are different
so the compiler must be able to choose correct function

the write_binary name in the class declarative scope hides the global write_binary name; in general, the compiler will traverse the "scope tree" from leaf to nodes and it will stop as soon as a node has been fully traversed and a set of candidate names has been found. The actual (function,varaible,whatever) name is picked from that set only.

For example, in the code

void f(int x);

struct A { void f() { f(1); } };

at the point of f(1) call there's an "f" name in the class scope. The set of candidates for overload resolution becomes {A::f()}. Therefore a compiler error is raised.

Indeed, the same thing happens with variables:

class A{ public: A(int x){ x=x; } private: int x; }

will not set the member variable x to the expected argument value ( but A(int x):x(x){} will do )