Mixin C

[Iain Buclaw]

On Friday, 8 March 2024 at 03:23:12 UTC, Paul Backus wrote:
> ```d
> module libwhatever;
>
> mixin(C) {
>     #include <libwhatever.h>
> }
> ```
>
> I haven't spent much time fleshing out the details of this 
> idea, but it seems pretty promising. What do you guys think?

The first thing that comes to mind is that it'll allow doing 
things inline that would otherwise be impossible in D.

```d
import std.stdio;

extern(C) int func(int x);

mixin(C) {
     // gdc supports these asm-declarations via gcc (ldc should 
too via clang)
     asm("
.globl func
     .type func, @function
     func:
     .cfi_startproc
     movl %edi, %eax
     addl $1, %eax
     ret
     .cfi_endproc
");
}

int main()
{
     int n = func(72);
     // mixin(C) not necessary as gdc+ldc support this natively 
with asm{""::;}
     mixin(C) {
         asm ("leal (%0,%0,4),%0"
              : "=r" (n)
              : "0" (n));
     }
     writeln("73*5 = ", n);  // 73*5 = 365

     // ditto, asm{""}, but this is purely for presentation.
     mixin(C) {
         asm ("movq $60, %rax\n"
              "movq $2,  %rdi\n"
              "syscall");
     }
     assert(0);
}
```