I'm a little new to the LLVM / LDC world, I'm looking forward to compiling a library with a C API that could be linked from not only D but also C or C++ project (through LLVM as well possibly).

I'm wondering if someone knows if this is something that's currently possible.

Thanks!

Should be possible:

extern(C)
int callme(int a)
{ return a; }

On Sunday, 25 May 2014 at 10:27:50 UTC, Kagamin wrote:
> Should be possible:
>
> extern(C)
> int callme(int a)
> { return a; }

Yes, right.

There is nothing special in using LDC here. There is even a recipe in the new D Cookbook on this topic (chapter 4, "Write part of a C proram in D"). Don't forget to initialize the D runtime from your C/C++ program.

Regards,
Kai

On 2014-05-26 02:16, Kai Nacke wrote:
> There is even a recipe in
> the new D Cookbook on this topic (chapter 4, "Write part of a C proram
> in D").

I'm waiting to get my copy ;)

> Don't forget to initialize the D runtime from your C/C++ program.

Would that mean I have to call rt_init() at the start of every function?

On Monday, 26 May 2014 at 12:50:59 UTC, Etienne Cimon wrote:
> On 2014-05-26 02:16, Kai Nacke wrote:
>> There is even a recipe in
>> the new D Cookbook on this topic (chapter 4, "Write part of a C proram
>> in D").
>
> I'm waiting to get my copy ;)
>
> > Don't forget to initialize the D runtime from your C/C++
> program.
>
> Would that mean I have to call rt_init() at the start of every function?

Do you mean calling D from C(++)? Ideally you call rt_init() only once, that's what I did when I wrote Python modules in C that linked to D code (C was only a thin wrapper). But I don't know how your program / application is structured.

Hi Etienne!

On Monday, 26 May 2014 at 12:50:59 UTC, Etienne Cimon wrote:
> On 2014-05-26 02:16, Kai Nacke wrote:
> Would that mean I have to call rt_init() at the start of every function?

No. Just call rt_init() before you call the first D function. You should also call rt_term() e.g. on program shutdown. This makes sure that the D runtime is initialized properly and that resources are freed on shutdown.
You should also make sure that no D exception escapes as C has no exception handling and D exceptions are not compatible with C++ exceptions.

Regards,
Kai

On 2014-05-26 12:33 PM, Kai Nacke wrote:
>
> No. Just call rt_init() before you call the first D function. You should
> also call rt_term() e.g. on program shutdown. This makes sure that the D
> runtime is initialized properly and that resources are freed on shutdown.
> You should also make sure that no D exception escapes as C has no
> exception handling and D exceptions are not compatible with C++ exceptions.
>
> Regards,
> Kai

I looked at the p.97 in the D Cookbook, and it calls rt_init() from C.

I was wondering, isn't it easier to put this initialization in a static this(), in the D module directly?

e.g. in test.d

import std.stdio, core.stdc.stdio : stderr;
extern(C) void helloC() nothrow; // a function from C

extern(C)
void helloD() nothrow {
	helloC();
	try {
		writeln("hello from D!");
	} catch(Throwable t) {
		fprintf(stderr, "writeln threw an exception.\n");
	}
}

static this(){
	rt_init();
}

On Friday, 30 May 2014 at 17:37:04 UTC, Etienne wrote:
> On 2014-05-26 12:33 PM, Kai Nacke wrote:
>>
>> No. Just call rt_init() before you call the first D function. You should
>> also call rt_term() e.g. on program shutdown. This makes sure that the D
>> runtime is initialized properly and that resources are freed on shutdown.
>> You should also make sure that no D exception escapes as C has no
>> exception handling and D exceptions are not compatible with C++ exceptions.
>>
>> Regards,
>> Kai
>
> I looked at the p.97 in the D Cookbook, and it calls rt_init() from C.
>
> I was wondering, isn't it easier to put this initialization in a static this(), in the D module directly?

AFAIK module constructors are called by runtime, so with absence of rt_init() those will have no effect.

On Friday, 30 May 2014 at 17:37:04 UTC, Etienne wrote:
>
> I was wondering, isn't it easier to put this initialization in a static this(), in the D module directly?

no. use pragma(LDC_global_crt_ctor).

fyi pyd builds shared libraries in the same way you want to

https://bitbucket.org/ariovistus/pyd/src/7fe2f9cf98da2fbd2b26bb30a5d93245c25ec742/infrastructure/d/python_so_linux_boilerplate.d?at=default

"Ellery Newcomer" <ellery-newcomer@utulsa.edu> writes:

> On Friday, 30 May 2014 at 17:37:04 UTC, Etienne wrote:
>>
>> I was wondering, isn't it easier to put this initialization in a static this(), in the D module directly?
>
> no. use pragma(LDC_global_crt_ctor).
>
> fyi pyd builds shared libraries in the same way you want to
>
> https://bitbucket.org/ariovistus/pyd/src/7fe2f9cf98da2fbd2b26bb30a5d93245c25ec742/infrastructure/d/python_so_linux_boilerplate.d?at=default

LDC also uses global ctors to build the ModuleInfo list.  A problem with calling rt_init() in a global ctor means that ModuleInfo is probably incomplete, meaning some or no module ctors (static this) are called.  I thought perhaps the LDC_global_crt_ctor optional priority arg could help, but makes no difference on OSX at least.
-- 
Dan