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jakacki@cidc.com.cn · Guest

Hello,

I would appreciate help and/or pointers to resources on the following
prolem: what does the Standard say about passing function
pointer/reference like this:

template <class F>
void get(const F& fun) {}

void f() {}

int main() { getFunction(f); }

* Is it legal?
* If so, what is the type of F inside make ?

These are the empirical results I got:

gcc-2.95:
OK, F is 'void ()()'

gcc-3.3.3:
no matching function for call to `get(void (&)())'

como-4.2.45.2:
no instance of function template "get" matches the argument list
The argument types that you used are: (void ())

como-4.3.3:
OK, F is 'void ()'

Any and all help appreciated.

Thank you in advance
Grzegorz

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pmdoc · Guest

Section 8.3.5.4 [dcl.fct] states:

"A cv-qualifier-seq shall only be part of the function type for a non-static
member function, the function type to which a pointer to member refers or
the top level function type of a function typedef declaration"

It gives the example:

typedef void F();

struct S {
const F f; // not equivalent to void f() const
};

In the case of get(const F&) it makes no sense to pass a non-member
function, thus gcc 3.3.3 and como-4.2.45.2: are correct (I use VC++ 7.1
which also behaves correctly in flagging this as an error).

Remeber 'const' refers to the type of the hidden 'this' parameter in the
signature of member functions only.

-- PMD

<jakacki (AT) cidc (DOT) com.cn> wrote