dyncall callback error when switching from 64 to 32 bit

Question

I have prepared a minimal reproducable example.

When I compile with 64 bit mingw and link to 64 bit versions of the dyncall libraries then the printed result is the expected 2.5000.

Switching both to 32 bit and after a make clean i get the printed result 0.0000.

The problem is only with dyn-callbacks, dyncalls seem to work fine.

#include <stdio.h>
#include <assert.h>
#include <dynload/dynload.h>
#include <dyncall/dyncall.h>
#include <dyncallback/dyncall_callback.h>

char mul_cbHandler ( DCCallback *cb,
        DCArgs *args, //DCArgs
        DCValue *result,
        void *userdata) {
    double a = dcbArgDouble(args);
    double b = dcbArgDouble(args);
    printf("got args: %f %f\n", a, b);
    result->d = a*b; // d: double
    return 'f'; // i or f
}

typedef double (*fptr_d_dd)(double x, double y);

void callbReceiver(fptr_d_dd fptr) {
    printf("res: %f\n", fptr(5.0f, 0.5f));
}
void testCallback() {
    DCCallVM* vm = dcNewCallVM(4096);
    assert(vm);
    DCCallback* pcb = dcbNewCallback("dd)d", mul_cbHandler, 0);
    assert(pcb);
    callbReceiver((fptr_d_dd)pcb);
    dcbFreeCallback(pcb);
    dcFree(vm);
}

int main(void) {
    testCallback();
    printf("q\n");
    return 0;
}

Answer 1

I wrote to the developer and got an immediate answer.

The version 0.9 manual.pdf nolonger limits return signature to i or f. We can specify d.

Confirmed that it works.