The D language page on interfacing to C
http://dlang.org/interfaceToC.html
says under 'Callbacks' that e.g.

  alias extern(C) int function(int, int) Callback;  // D code

is OK, so I am wondering if I can factor out the extern(C) from aliases as follows

  extern(C) {
    alias int function(int, int) Callback;
    // more aliases
  }

Is Callback here a name for the same type as if it was defined by the following?

  alias extern(C) int function(int, int) Callback;

On Thursday, 22 August 2013 at 23:55:44 UTC, Carl Sturtivant wrote:
> Is Callback here a name for the same type as if it was defined by the following?
>
>   alias extern(C) int function(int, int) Callback;

Yes. If you want to make sure, you can use a trait:

import std.traits;

extern(C) { void test1() { } }
void test2() { }

static assert(functionLinkage!test1 == "C");
static assert(functionLinkage!test2 != "C");  // D calling convention

On Friday, 23 August 2013 at 00:00:13 UTC, Andrej Mitrovic wrote:
> On Thursday, 22 August 2013 at 23:55:44 UTC, Carl Sturtivant wrote:
>> Is Callback here a name for the same type as if it was defined by the following?
>>
>>  alias extern(C) int function(int, int) Callback;
>
> Yes. If you want to make sure, you can use a trait:
>
> import std.traits;
>
> extern(C) { void test1() { } }
> void test2() { }
>
> static assert(functionLinkage!test1 == "C");
> static assert(functionLinkage!test2 != "C");  // D calling convention

Nice! Thank you.

On 2013-08-23 02:00, Andrej Mitrovic wrote:

> static assert(functionLinkage!test2 != "C");  // D calling convention

Or Windows, Pascal or C++.

-- 
/Jacob Carlborg

On 8/23/13, Jacob Carlborg <doob@me.com> wrote:
> On 2013-08-23 02:00, Andrej Mitrovic wrote:
>
>> static assert(functionLinkage!test2 != "C");  // D calling convention
>
> Or Windows, Pascal or C++.

I'd prefer if functionLinkage returned an enum, it's too easy to write "c" instead of "C" in some generic code and have a static if branch not taken.

On 2013-08-23 13:10, Andrej Mitrovic wrote:

> I'd prefer if functionLinkage returned an enum, it's too easy to write
> "c" instead of "C" in some generic code and have a static if branch
> not taken.

Yeah, that's a good point.

-- 
/Jacob Carlborg