I'd like to be able to use GCC's `__builtin_alloca` without the C standard library.

This seems to work:

--- core/stdc/stdlib.d
module core.stdc.stdlib;
extern(C) void* alloca(size_t n) pure;
---

...but, since I'm not actually using the C standard library, I'd prefer to avoid creating that module hierarchy.


I tried simply adding...

--- {anyfile}.d
extern extern(C) void* __builtin_alloca(size_t size) pure;
---

... to my existing files, but I get an undefined reference for `__bulitin_alloca`.


LDC was pretty straightforward with:
--- {anyfile}.d
pragma(LDC_alloca)
void* alloca(size_t size) pure;
---

Is there a way to do something like that in GDC.  I don't care if I have to use `__builtin_alloca` or some other identifier, I just don't want to create the C standard library module hierarchy.

Thanks,
Mike

Am Mon, 23 Jul 2018 01:35:02 +0000 schrieb Mike Franklin:

> I'd like to be able to use GCC's `__builtin_alloca` without the C standard library.
> 

Just import gcc.builtins for all GCC builtins:

----------------------------
import gcc.builtins;

void main()
{
    auto foo = __builtin_alloca(10);
}
----------------------------

-- 
Johannes

On 23 July 2018 at 09:15, Johannes Pfau via D.gnu <d.gnu@puremagic.com> wrote:
> Am Mon, 23 Jul 2018 01:35:02 +0000 schrieb Mike Franklin:
>
>> I'd like to be able to use GCC's `__builtin_alloca` without the C standard library.
>>
>
> Just import gcc.builtins for all GCC builtins:
>
> ----------------------------
> import gcc.builtins;
>
> void main()
> {
>     auto foo = __builtin_alloca(10);
> }
> ----------------------------
>

Assuming that you are already using the gcc.attribute module for accessing various attributes, possibly via a wrapper module.

There's probably a project to be made for adding pragmas as an alternative to the various magic modules and attributes we have in the compiler, but first requires a little nip and tuck to make it more friendly for us to add these to gdc.

https://issues.dlang.org/show_bug.cgi?id=3004 https://issues.dlang.org/show_bug.cgi?id=19108 https://issues.dlang.org/show_bug.cgi?id=19109 https://issues.dlang.org/show_bug.cgi?id=19110

As well as 'pragma(GNU_builtin)', there are these such options that
can't be done using UDAs.

https://gcc.gnu.org/onlinedocs/gcc/Loop-Specific-Pragmas.html

Iain.