Hey guys!

I am working on a binding for D, and am almost finished! I started to think of some things I might like to work on to improve the binding after I get everything working, and one of the things I thought of was rewriting certain parts to use only D code instead of making calls to the C functions. Is there any kind of performance overhead in using C libraries to interact with your D program? If it isn't going to offer much performance gain then I probably don't need to bother writing extra code.

Thanks as usual!

On 03/14/2013 01:48 AM, Jeremy DeHaan wrote:
> Hey guys!
>
> I am working on a binding for D, and am almost finished! I started to
> think of some things I might like to work on to improve the binding
> after I get everything working, and one of the things I thought of was
> rewriting certain parts to use only D code instead of making calls to
> the C functions. Is there any kind of performance overhead in using C
> libraries to interact with your D program? If it isn't going to offer
> much performance gain then I probably don't need to bother writing extra
> code.
>
> Thanks as usual!

There is no additional overhead (though the D compiler will not be able to inline C functions, whereas an identical D function may be inlined.)

On Thursday, 14 March 2013 at 00:48:53 UTC, Jeremy DeHaan wrote:
> Hey guys!
>
> I am working on a binding for D, and am almost finished!

Are you going to publish this binding? Which library?

On 03/14/13 01:52, Timon Gehr wrote:
> On 03/14/2013 01:48 AM, Jeremy DeHaan wrote:
>>
>> I am working on a binding for D, and am almost finished! I started to think of some things I might like to work on to improve the binding after I get everything working, and one of the things I thought of was rewriting certain parts to use only D code instead of making calls to the C functions. Is there any kind of performance overhead in using C libraries to interact with your D program? If it isn't going to offer much performance gain then I probably don't need to bother writing extra code.
> 
> There is no additional overhead (though the D compiler will not be able to inline C functions, whereas an identical D function may be inlined.)

Like Timon said - there's is zero overhead.
Even the inlining limitation only applies to /some/ compilers. [1]


xlanginline1.d:
   extern extern(C) int c();
   int main() { return 2*c(); }

xlanginline2.c:
   int c() { return 21; };

compiled with GDC + -flto:

08049820 <_Dmain>:
 8049820:       55                      push   %ebp
 8049821:       b8 2a 00 00 00          mov    $0x2a,%eax
 8049826:       89 e5                   mov    %esp,%ebp
 8049828:       5d                      pop    %ebp
 8049829:       c3                      ret

artur

[1] and versions, unfortunately.

On Thursday, 14 March 2013 at 00:52:41 UTC, Timon Gehr wrote:
> On 03/14/2013 01:48 AM, Jeremy DeHaan wrote:
>> Hey guys!
>>
>> I am working on a binding for D, and am almost finished! I started to
>> think of some things I might like to work on to improve the binding
>> after I get everything working, and one of the things I thought of was
>> rewriting certain parts to use only D code instead of making calls to
>> the C functions. Is there any kind of performance overhead in using C
>> libraries to interact with your D program? If it isn't going to offer
>> much performance gain then I probably don't need to bother writing extra
>> code.
>>
>> Thanks as usual!
>
> There is no additional overhead (though the D compiler will not be able to inline C functions, whereas an identical D function may be inlined.)

A decent link-time optimiser will be able to do the inlining where appropriate. gdc can be compiled with lto enabled, as Artur shows in his reply.