ambiguity in function overloading

Hi all,

Now I am learning about the ambiguity in function overloading.

So I written a small program

void f1( long a )

{

}

void f1(char a )

{

}

void Somefunc()

{

Int b = 20000;

f1( b );

}

Here my compiler (VC 2010) complaining the call is ambiguous.

But I think according to the overloading rules promotions have more priority than standard conversions.

Here I think int to char have data lose and definitely needs the standard conversion.

But I don’t think int to long have any data lose (I think according to C++ standards long will be always bigger than int in size)

So I think int to long only need a promotion. Am I right?

If it only needs a promotion how the above function call is ambiguous? Compiler can clearly choose the f1 (long) na?

please help me to understand the concepts