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D.gnu - Using GCC's builtin alloca without the C standard library

reply Mike Franklin <slavo5150 yahoo.com> writes:
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
Jul 22 2018
parent reply Johannes Pfau <nospam example.com> writes:
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
Jul 23 2018
parent Iain Buclaw <ibuclaw gdcproject.org> writes:
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.
Jul 23 2018