A friend of mine is trying to figure out the D equivalent of using macros with asm blocks in C:

#define NEXT() __asm__("jmp *%0"::"r"((++ip)->jmp)); goto *ip->jmp

D's asm blocks are very restrictive: mixins are not allowed. What do you do in D?

Thank you,
Ali

On Wed, Jan 30, 2013 at 4:01 PM, Ali Çehreli <acehreli@yahoo.com> wrote:
> A friend of mine is trying to figure out the D equivalent of using macros with asm blocks in C:
>
> #define NEXT() __asm__("jmp *%0"::"r"((++ip)->jmp)); goto *ip->jmp
>
> D's asm blocks are very restrictive: mixins are not allowed. What do you do in D?

Is it possible to enclose an asm statement into a mixin?

mixin("
asm {

....

code to include

}");

On 01/30/2013 11:08 AM, Philippe Sigaud wrote:
> On Wed, Jan 30, 2013 at 4:01 PM, Ali Çehreli<acehreli@yahoo.com>  wrote:
>> A friend of mine is trying to figure out the D equivalent of using macros
>> with asm blocks in C:
>>
>> #define NEXT() __asm__("jmp *%0"::"r"((++ip)->jmp)); goto *ip->jmp
>>
>> D's asm blocks are very restrictive: mixins are not allowed. What do you do
>> in D?
>
> Is it possible to enclose an asm statement into a mixin?
>
> mixin("
> asm {
>
> ....
>
> code to include
>
> }");

Thanks!

It is almost there, except that one needs to use a compile-time "macro expansion" solution, which I am too lazy to try now. :) I am confident that the following program will work after doing that. (Of course also after replacing 'writeln' with 'mixin'.)

import std.stdio;
import std.regex;

string expandNexts(string input)
{
    enum e = ctRegex!("Next;", "g");
    // NOTE: This is an example. Of course, the second string below should be
    // whatever the "macro" should be expanded as.
    return replace(input, e, "cmp EAX,0;");
}

void main()
{
    writeln (expandNexts(q{
        asm
        {
            mov EAX, 10000;
            Next;
            Next;
            Next;
            Next;
            Next;
        }
    }));
}

The program prints

        asm
        {
            mov EAX, 10000;
            cmp EAX,0;
            cmp EAX,0;
            cmp EAX,0;
            cmp EAX,0;
            cmp EAX,0;
        }

Ali