I have this function:
----
void foo(T)(void function(T*) test) { }
----

And want to call it with a C function:
----
foo!(SDL_Surface)(SDL_FreeSurface);
----

but I get:
Fehler	1	Error: foo (void function(SDL_Surface*) test) is not callable using argument types (extern (C) void function(SDL_Surface*) nothrow)

What would be the smartest solution?

Am 10.10.2013 16:13, schrieb Namespace:
> I have this function:
> ----
> void foo(T)(void function(T*) test) { }
> ----
>
> And want to call it with a C function:
> ----
> foo!(SDL_Surface)(SDL_FreeSurface);
> ----
>
> but I get:
> Fehler    1    Error: foo (void function(SDL_Surface*) test) is not
> callable using argument types (extern (C) void function(SDL_Surface*)
> nothrow)
>
> What would be the smartest solution?

If you can change the signature of foo just add a extern(c) to the function pointer declaration.

Otherwise just wrap the SDL_FreeSurface call into a delegate on the caller side.

-- 
Kind Regards
Benjamin Thaut

On Thursday, 10 October 2013 at 14:13:47 UTC, Namespace wrote:
> I have this function:
> ----
> void foo(T)(void function(T*) test) { }
> ----
>
> And want to call it with a C function:
> ----
> foo!(SDL_Surface)(SDL_FreeSurface);
> ----
>
> but I get:
> Fehler	1	Error: foo (void function(SDL_Surface*) test) is not callable using argument types (extern (C) void function(SDL_Surface*) nothrow)
>
> What would be the smartest solution?

Wrap it in a lambda. Or change foo() signature to accept `extern(C)` functions - you can't just mix calling convention.

On Thursday, 10 October 2013 at 14:26:37 UTC, Benjamin Thaut wrote:
> Am 10.10.2013 16:13, schrieb Namespace:
>> I have this function:
>> ----
>> void foo(T)(void function(T*) test) { }
>> ----
>>
>> And want to call it with a C function:
>> ----
>> foo!(SDL_Surface)(SDL_FreeSurface);
>> ----
>>
>> but I get:
>> Fehler    1    Error: foo (void function(SDL_Surface*) test) is not
>> callable using argument types (extern (C) void function(SDL_Surface*)
>> nothrow)
>>
>> What would be the smartest solution?
>
> If you can change the signature of foo just add a extern(c) to the function pointer declaration.
>
> Otherwise just wrap the SDL_FreeSurface call into a delegate on the caller side.

You mean like this?
----
void foo(T)(extern(C) void function(T*) func) {
		
}
----

That prints: Error: basic type expected, not extern	

On Thursday, 10 October 2013 at 14:28:20 UTC, Dicebot wrote:
> On Thursday, 10 October 2013 at 14:13:47 UTC, Namespace wrote:
>> I have this function:
>> ----
>> void foo(T)(void function(T*) test) { }
>> ----
>>
>> And want to call it with a C function:
>> ----
>> foo!(SDL_Surface)(SDL_FreeSurface);
>> ----
>>
>> but I get:
>> Fehler	1	Error: foo (void function(SDL_Surface*) test) is not callable using argument types (extern (C) void function(SDL_Surface*) nothrow)
>>
>> What would be the smartest solution?
>
> Wrap it in a lambda.

Example? I do not use lambdas often.

On Thursday, 10 October 2013 at 14:40:09 UTC, Namespace wrote:
> Example? I do not use lambdas often.

void foo(T)(void function(T*) test)
{
}

extern(C) void bar(int*) { }

void main()
{
	foo( (int* a) => bar(a) );
}

I don't know to what extent IFTI can work here though.

Namespace:

> You mean like this?
> ----
> void foo(T)(extern(C) void function(T*) func) {
> 		
> }
> ----
>
> That prints: Error: basic type expected, not extern	

In theory that's correct, in practice the compiler refuses that, it's in Bugzilla, so try to define the type outside the signature (untested):

alias TF = extern(C) void function(T*);

void foo(T)(TF func) {}

Bye,
bearophile

On Thursday, 10 October 2013 at 15:15:45 UTC, bearophile wrote:
> Namespace:
>
>> You mean like this?
>> ----
>> void foo(T)(extern(C) void function(T*) func) {
>> 		
>> }
>> ----
>>
>> That prints: Error: basic type expected, not extern	
>
> In theory that's correct, in practice the compiler refuses that, it's in Bugzilla, so try to define the type outside the signature (untested):
>
> alias TF = extern(C) void function(T*);
>
> void foo(T)(TF func) {}
>
> Bye,
> bearophile

/d917/f732.d(8): Error: basic type expected, not extern
/d917/f732.d(8): Error: semicolon expected to close alias declaration
/d917/f732.d(8): Error: no identifier for declarator void function(T*)

On Thursday, 10 October 2013 at 14:44:00 UTC, Dicebot wrote:
> On Thursday, 10 October 2013 at 14:40:09 UTC, Namespace wrote:
>> Example? I do not use lambdas often.
>
> void foo(T)(void function(T*) test)
> {
> }
>
> extern(C) void bar(int*) { }
>
> void main()
> {
> 	foo( (int* a) => bar(a) );
> }
>
> I don't know to what extent IFTI can work here though.

That works. Thanks.

Namespace:

> /d917/f732.d(8): Error: basic type expected, not extern
> /d917/f732.d(8): Error: semicolon expected to close alias declaration
> /d917/f732.d(8): Error: no identifier for declarator void function(T*)

It seems that even the new alias syntax doesn't support the extern :-) Perhaps this bug is not yet in Bugzilla.

Try:

alias extern(C) void function(T*) TF;
void foo(T)(TF func) {}

Bye,
bearophile