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digitalmars.D - How to make D libraries callable from C?

reply %u <alainpoint yahoo.fr> writes:
Hello,
I am a D newbie and my company makes heavy use of C. I would like to
demonstrate that the D language can be beneficial much more than Java.
My question is: is it possible to make a library, that is callable
from C? I guess i would have to write the corresponding .h file for
inclusion, with possibly a C-wrapper around the D classes.
Thank you for helping.

Alain
Dec 18 2006
parent reply Gregor Richards <Richards codu.org> writes:
%u wrote:

 Hello,
 I am a D newbie and my company makes heavy use of C. I would like to
 demonstrate that the D language can be beneficial much more than Java.
 My question is: is it possible to make a library, that is callable
 from C? I guess i would have to write the corresponding .h file for
 inclusion, with possibly a C-wrapper around the D classes.
 Thank you for helping.
 
 Alain


All you need is to use extern (C) on those functions you want to be 
callable from C.

D:

extern (C) void doStuff(int withThis) { ... }


C header:
void doStuff(int);

  - Gregor Richards
Dec 18 2006
parent reply Brad Roberts <braddr puremagic.com> writes:
Gregor Richards wrote:

 %u wrote:

 Hello,
 I am a D newbie and my company makes heavy use of C. I would like to
 demonstrate that the D language can be beneficial much more than Java.
 My question is: is it possible to make a library, that is callable
 from C? I guess i would have to write the corresponding .h file for
 inclusion, with possibly a C-wrapper around the D classes.
 Thank you for helping.

 Alain


 
 All you need is to use extern (C) on those functions you want to be 
 callable from C.
 
 D:
 
 extern (C) void doStuff(int withThis) { ... }
 
 
 C header:
 void doStuff(int);
 
  - Gregor Richards


There's more to it than that.

The D runtime will need to be initialized unless special care is taken 
to avoid anything that's going to touch the GC or anything else that 
requires initialization. (it's been a while since I looked at that part 
of phobos/ares.

You'll have to be careful to keep the interfaces to mutually compatible 
data types.  D doesn't prevent you from writing something like:

     extern (C) char[] someFunc(SomeClass a, SomeAlias b, SomeDelegate c)

Essentially all the extern C part does is drop the name mangling.

Don't let exceptions leak out of this D/C barrier.. C doesn't know 
anything about exceptions.  If instead of C you really meant C++, the 
same still applies except with dmd on windows.  Every other combination 
of language/compiler/os is currently incompatible, though I'd love to 
see this fixed.

There might be something else that needs to be handled as well, but 
those are the things that come to mind quickly.

Later,
Brad
Dec 18 2006
parent reply Alain <alainpoint yahoo.fr> writes:
== Quote from Brad Roberts (braddr puremagic.com)'s article

 There's more to it than that.
 The D runtime will need to be initialized unless special care is


taken

 to avoid anything that's going to touch the GC or anything else that
 requires initialization. (it's been a while since I looked at that


part

 of phobos/ares.
 You'll have to be careful to keep the interfaces to mutually


compatible

 data types.  D doesn't prevent you from writing something like:
      extern (C) char[] someFunc(SomeClass a, SomeAlias b,


SomeDelegate c)

 Essentially all the extern C part does is drop the name mangling.
 Don't let exceptions leak out of this D/C barrier.. C doesn't know
 anything about exceptions.  If instead of C you really meant C++,


the

 same still applies except with dmd on windows.  Every other


combination

 of language/compiler/os is currently incompatible, though I'd love


to

 see this fixed.
 There might be something else that needs to be handled as well, but
 those are the things that come to mind quickly.
 Later,
 Brad


All you warn me against seems reasonable. D being a higher-level
language than C, you have to down-grade it by writing a wrapper
around the D library in order to make it understandable by the C
application.
What i miss however is what you call the 'D runtime' initialisation.
Could you give a concrete example of what needs to be done.
Thanks in advance
Alain
Dec 19 2006
parent "Tomas Lindquist Olsen" <tomas famolsen.dk> writes:
Alain wrote:


 == Quote from Brad Roberts (braddr puremagic.com)'s article

 There's more to it than that.
 The D runtime will need to be initialized unless special care is


 taken

 to avoid anything that's going to touch the GC or anything else that
 requires initialization. (it's been a while since I looked at that


 part

 of phobos/ares.
 You'll have to be careful to keep the interfaces to mutually


 compatible

 data types.  D doesn't prevent you from writing something like:
      extern (C) char[] someFunc(SomeClass a, SomeAlias b,


 SomeDelegate c)

 Essentially all the extern C part does is drop the name mangling.
 Don't let exceptions leak out of this D/C barrier.. C doesn't know
 anything about exceptions.  If instead of C you really meant C++,


 the

 same still applies except with dmd on windows.  Every other


 combination

 of language/compiler/os is currently incompatible, though I'd love


 to

 see this fixed.
 There might be something else that needs to be handled as well, but
 those are the things that come to mind quickly.
 Later,
 Brad


 
 All you warn me against seems reasonable. D being a higher-level
 language than C, you have to down-grade it by writing a wrapper
 around the D library in order to make it understandable by the C
 application.
 What i miss however is what you call the 'D runtime' initialisation.
 Could you give a concrete example of what needs to be done.
 Thanks in advance
 Alain


The Win32 DLL in D article at digitalmars.com sums it up pretty well I
think:

http://www.digitalmars.com/d/dll.html

--
Dec 19 2006