Re: [Mingw-users] Can a DLL call the function built in main program?

[Lloyd D. <ll...@no...>]

I don't understand, why don't you simply do something like that?
Works well wether you use DLL or not...
#-- pseudo code below ---------
typedef void (*CALLBACK)(...);

static CALLBACK feeback = NULL;

DLL_EXPORT void SetCallBack(CALLBACK calback)
{
    feedback = cakkback;
}
DLL_EXPORT call_me_back(param_list_t plt)
{
    // ......
    if(feedback != null)
        feedback(params);
}
#---------------------------------

----- Original Message ----- 
From: "zhong wang" <zho...@gm...>
To: <min...@li...>
Sent: Wednesday, May 25, 2005 8:57 AM
Subject: Re: [Mingw-users] Can a DLL call the function built in main 
program?


Thanks, Brian

Actually I have little understanding on Windows DLL. I am porting a
plugin system from Linux to Netware and Windows. On Linux there is a
simple option -rdynamic with gcc can make this work. On netware, just
simply add the export list and import list while compiling to make it
works.  I googled a lot about MinGW DLL, and tried to figure out if
Windows can implement in a similar way.

In you example,  the name of .exe will never be changed. Is it
possible to get a flexible solution with .def file or some other ways
else?

My code should be like:

$ cat >main.c <<EOF
#include <windows.h>
#include <stdio.h>
void call_func_in_main()
{
        printf("Get function in main program\n");
        return;
}
int main ()
{
        typedef void (*pfunc)();

        HANDLE hdll;

        pfunc hello;

        hdll = LoadLibrary("tst.dll");

        hello = (pfunc)GetProcAddress(hdll, "hello");

        hello();
        return 0;
}
<<EOF

$ cat >tst.c <<EOF

#include <stdio.h>
#include <windows.h>
extern void call_func_in_main();
DECLSPEC_EXPORT void hello(void)
{
        call_func_in_main();
        printf ("Hello\n");
}
<<EOF

On 5/24/05, Brian Dessent <br...@de...> wrote:
> zhong wang wrote:
> >
> > Thanks for response.
> >
> > I am talking about doing LoadLibrary and GetProcAddress by hand. I am
> > working on a "real" dynamic library.  Any other advices?
>
> If that's what you're really doing then why did all the examples you
> posted in your message just try to do regular dynamic linking?  I don't
> understand why you would bother bringing up any of that if you are
> indeed using LoadLibrary and GetProcAddress.  Just to be clear, you
> don't have to go down the road of LoadLibrary if you don't want to, your
> DLL can in fact call functions in the main exe, with the caveat that it
> adds the requirement that the name of the .exe never change.
>
> $ cat >getprocaddr_dll.c <<EOF
> #include <windows.h>
> #include <stdio.h>
>
> DECLSPEC_EXPORT int i_am_a_dll_function (int x)
> {
>   int (*i_am_a_main_function) (int);
>   HINSTANCE hm;
>
>   if ((hm = LoadLibrary ("getprocaddr_main.exe")) == NULL)
>     perror ("LoadLibrary dll");
>
>   if ((i_am_a_main_function = GetProcAddress (hm,
> "i_am_a_main_function")) == NULL)
>     perror ("GetProcAddress dll");
>
>   return i_am_a_main_function (x * 10);
> }
> EOF
>
> $ cat >getprocaddr_main.c <<EOF
> #include <windows.h>
> #include <stdio.h>
>
> DECLSPEC_EXPORT int i_am_a_main_function (int x)
> {
>   return x * 50;
> }
>
> int main (void)
> {
>   int (*i_am_a_dll_function) (int);
>   HINSTANCE hm;
>
>   if ((hm = LoadLibrary ("getprocaddr_dll.dll")) == NULL)
>     perror ("LoadLibrary main");
>
>   if ((i_am_a_dll_function = GetProcAddress (hm, "i_am_a_dll_function"))
> == NULL)
>     perror ("GetProcAddress main");
>
>   printf ("%d\n", i_am_a_dll_function (42));
> }
> <<EOF
>
> $ gcc -shared getprocaddr_dll.c -o getprocaddr_dll.dll
> $ gcc getprocaddr_main.c -o getprocaddr_main
> $ ./getprocaddr_main
> 21000
>
>
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