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Date: Wed, 13 Jul 2005 08:35:52 -0700 (PDT)
Message-Id: <200507131535.j6DFZqwi005679@diometes.ucdavis.edu>
To: cygwin AT cygwin DOT com
Subject: How to create a .dll which contains a function defined in another program?
From: "Yu-Cheng Chou" <cycchou AT ucdavis DOT edu>
X-Errors-To: cycchou AT magenta DOT ucdavis DOT edu
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Hi,

bar() is in the main.c which is compiled using VC++.
bar() is called inside module.c which is compiled as module.dll using 
cygwin's gcc. 
module.dll is loaded by LoadLibrary() in main.exe.

/* main.c */
#include <stdio.h>
#include <windows.h>

extern "C" int mainCRTStartup();

extern "C" int __stdcall 
cygloadCRTStartup() {
    char padding[4096];
    return mainCRTStartup();
}

__declspec(dllexport)
int bar() {
    printf("bar() is called\n");
    return 0;
}

int main() {   
    char *modname = "module.dll";  
    HMODULE h;
    HMODULE handle;
    void (*init)();
    int (*fp)(int);
    int ret;

    h = LoadLibrary("cygwin1.dll");
    init = (void (*)())GetProcAddress(h, "cygwin_dll_init");
    init();
    handle = LoadLibrary(modname);
    fp = (int (*)(int))GetProcAddress(handle, "foo");
    ret = fp(125);
    printf("ret = %d\n", ret);
    return 0;
}

/* module.c */
#include <stdio.h>

extern __declspec(dllimport)
int bar();

__declspec(dllexport)
int foo(int arg){   
   printf("foo() is called in main.exe\n");
   printf("arg * 2 = %d\n", arg * 2);
   printf("\n");
   bar();
   return arg * 2;
}

Thanks


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