• Mildred (33/33) Sep 07 2006 Hi,
• Don Clugston (9/20) Sep 07 2006 extern (C) {
• Mildred (8/18) Sep 07 2006 Thanks for the answer,
• Stewart Gordon (20/38) Sep 19 2006

Mildred <mildred593 online.fr> writes:

Hi,

In my application, I want to be able to extand it using regular C
objects, loaded using for example dlfcn for POSIX systems (maybe
another way on Windows).
So, I need to have C functions pointers but I don't know how to declare
them correctly :

/////////// test.d ///////////

module test;

extern(C){
    int c_function(int param){
        return param;
    }
}

int main(){
    // create a pointer to c_function
    extern (C) int function(int) ptr = &c_function;
    extern (C) int (*ptr2)(int)      = &c_function;
    return 0;
}

//////////////////////////////

$ dmd test.d
test.d(35): cannot implicitly convert expression (& c_function) of type
int(C *)(int param) to int(*)(int)
test.d(36): cannot implicitly convert expression (& c_function) of type
int(C *)(int param) to int(*)(int)

So, How do we do that , I did not find neither on the documentation nor
while browsing the web for the solution.
Thanks

Mildred

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Don Clugston <dac nospam.com.au> writes:

Mildred wrote:
 Hi,
 
 So, I need to have C functions pointers but I don't know how to declare
 them correctly :

It's easiest to typedef them; the typedef picks up the extern(C).

 module test;
 
 extern(C){
     int c_function(int param){
         return param;
     }
 }

extern (C) {
   typedef int function(int) CFuncPtr;
}

void main() {
    CFuncPtr ptr = &c_function;
}


BTW, this type of question really belongs in the 'D.learn' newgroup.

Mildred <mildred593 online.fr> writes:

 extern (C) {
    typedef int function(int) CFuncPtr;
 }
 
 void main() {
     CFuncPtr ptr = &c_function;
 }
 
 
 BTW, this type of question really belongs in the 'D.learn' newgroup.

Thanks for the answer,
I didn't knew in which newsgroup I had to post, so I posted here,
thanks for that clarification. I'll post there the next time.

Mildred
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Clef GPG :    <hkp://pgp.mit.edu> ou <http://mildred632.free.fr/gpg_key>
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Stewart Gordon <smjg_1998 yahoo.com> writes:

Don Clugston wrote:
 Mildred wrote:
 Hi,

 So, I need to have C functions pointers but I don't know how to declare 
 them correctly :

 
 It's easiest to typedef them; the typedef picks up the extern(C).

Or alias them.

 module test;

 extern(C){
     int c_function(int param){
         return param;
     }
 }

 
 extern (C) {
   typedef int function(int) CFuncPtr;
 }

<snip>

I see.  So

     extern (C) int function(int) ptr = &c_function;

merely gives the symbol ptr C linkage, and doesn't affect the linkage of 
the function involved?

There ought to be a way of giving function pointer types linkage 
attributes inline.  Maybe

     int extern (C) function(int) ptr = &c_function;

or something...?

Stewart.

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