Question and Answer Database
FAQ4433C.txt :Cannot convert 'void (* (_closure )())()' to 'void (MyClass::*)()'
Category :Compiler
Platform :All-32Bit
Product :All-CBuilder,
Question:
Why am I getting the error:
Cannot convert 'void (* (_closure )())()' to 'void (MyClass::*)()'
I'm not even using the VCL or closures in my program!
Answer:
This is likely a programming error on your part. If you are trying
to use a pointer to a non-static member function, check the syntax
to ensure you are following the C++ rules for taking the address of
a member function.
Before C++Builder, your code would have got the more descriptive
error message 'function must be called or its address taken'. But in
C++Builder it is perfectly valid to take the address of a non-static
member function using the same syntax as for taking the address of a
non-member function (or a static member function): That's the syntax
for accessing a closure. A closure is a non-static member function
that does not need to be bound to an object.
// To see an example of how not to take the address of a non-static member
// function, compile with:
// bcc32
// To see the correct way, compile with:
// bcc32 -DCORRECT
//
struct Sonne
{
typedef void (Sonne::*SonnePtr)();
void gdj(){}
void bmj( SonnePtr p ){}
Sonne()
{
#ifdef CORRECT
bmj( &Sonne::gdj );
#else
bmj( &gdj ); // valid for closures, not non-static member functions!
// -or-
// bmj( gdj ); // valid for closures, not non-static member functions!
#endif
}
};
3/11/99 10:55:56 AM
Last Modified: 01-SEP-99