C++ interworking

[Jamie]

It could be that I'm doing something silly, but I can't see it. I'm trying to call a C++ function from an XC program as follows:

main.xc:

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#include "functions.h"

int main(void) {
    chan c;
    par {
        send(c);
        receive(c);
    }
    return 0;
}

functions.h:

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void send(chanend c);
void receive(chanend c);

functions.cpp:

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#include <xccompat.h>
#include "channels.h"

void send(chanend c) {
    while(1) {
        chanOut(c, 0);
    }
}

void receive(chanend c) {
    while(1) {
        chanIn(c);
    }
}

channels.h:

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void chanOut(chanend c, unsigned v);
void chanIn(chanend c);

channels.xc:

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#include "channels.h"

void chanOut(chanend c, unsigned v) {
    c <: v;
}

void chanIn(chanend c) {
    unsigned v;
    c :> v;
}

Build:

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xcc -target=XC-1 -c channels.xc
xcc -target=XC-1 -c main.xc
xcc -target=XC-1 -std=c++98 -c functions.cpp
xcc -target=XC-1 main.o functions.o channels.o

Gives the error:

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xmap: Error: Value of undefined resource symbol "send.nstackwords" cannot be determined.
xmap: Error: Symbol "send.nstackwords" for resolution of resource expression for ".LLNK6" is undefined.

Then commenting out sender and receiver from the main par gives:

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functions.cpp: Error: Undefined reference to '_Z6chanInj'
functions.cpp: Error: Undefined reference to '_Z7chanOutjj'

Does anyone have any ideas?

[richard]

You need to give the c++ function you want to call C linkage to avoid C++ name mangling. For example you can change functions.h as follows:

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#ifdef __cplusplus
extern "C" {
#endif

void send(chanend c);
void receive(chanend c);

#ifdef __cplusplus
} // extern "C"
#endif

You would run into exactly the same problem if you tried to call between C and C++ without the extern "C" construct, for example see http://www.parashift.com/c++-faq-lite/m ... d-cpp.html

[monk_is_batman]

You'll also need include the header file functions.h in your functions.cpp file. As well as make the same changes to your channels.h, I've attached the project I was working in trying to get this work in. It compiles for me.

[Jamie]

You need to give the c++ function you want to call C linkage to avoid C++ name mangling.

Oh okay. I didn't know about that happening... Thanks though, all working now :)