Question about function aliases

[Gary Willoughby]

On Thursday, 12 December 2013 at 00:51:56 UTC, dnewbie wrote:
> On Wednesday, 11 December 2013 at 23:42:44 UTC, Gary Willoughby 
> wrote:
>> For example i have some C code like this:
>>
>> typedef void (Tcl_InterpDeleteProc) _ANSI_ARGS_((ClientData 
>> clientData, Tcl_Interp *interp));
>>
>> void Tcl_CallWhenDeleted(Tcl_Interp* interp, 
>> Tcl_InterpDeleteProc* proc, ClientData clientData);
>>
>>
>> I intend on converted this to D thus:
>>
>> alias void function(ClientData clientData, Tcl_Interp* interp) 
>> Tcl_InterpDeleteProc;
>>
>> void Tcl_CallWhenDeleted(Tcl_Interp* interp, 
>> Tcl_InterpDeleteProc* proc, ClientData clientData);
>>
>> Is it correct keeping the * with the Tcl_InterpDeleteProc 
>> parameter or do i remove it? Is the alias above a function 
>> pointer?
>>
>> To call this function can i use a function literal for the 
>> Tcl_InterpDeleteProc parameter? or do i need to pass an 
>> address of the function?
>
> It's a function pointer.
> Test:
>
> import std.stdio;
> alias extern(C) void function(void*) Callback;
>
> void Call(Callback c)
> {
>     c(c);
> }
>
> extern(C) void callback(void* v)
> {
>     writefln("v: %04X", v);
> }
> 	
> void main()
> {
>     Callback c = &callback;
>     Call(c);	
>     writefln("c: %04X", c);
> }

So i guess i need to remove the * after the Tcl_InterpDeleteProc 
parameter from the C declaration when porting it?

Using the * my tests show an error which i guess is caused by the 
declaration expecting a pointer to a function pointer.

Here is my test:

import std.stdio;

// Function pointer type.
alias void function(string text, int level) Tcl_InterpDeleteProc;

// A function that uses the function pointer type for a parameter.
void test(Tcl_InterpDeleteProc func) // <-- no *
{
	(*func)("Hello", 100);
}

// A callback that going to be used as the parameter.
void callback(string text, int level)
{
	writefln("text : %s", text);
	writefln("level: %d", level);
}

// test.
void main(string[] args)
{
	// Use address of function.
	test(&callback);

	// Function literal passed as pointer.
	test(function(string text, int level){
		writefln("text : %s", text);
		writefln("level: %d", level);
	});
}

After testing i've decided on the following code for the port. 
Would you agree this is correct?

alias void function(ClientData clientData, Tcl_Interp* interp)  
Tcl_InterpDeleteProc;

extern (C) void Tcl_CallWhenDeleted(Tcl_Interp* interp, 
Tcl_InterpDeleteProc proc, ClientData clientData);