Re: 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);