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From: "Andrej Borsenkow" <Andrej DOT Borsenkow AT mow DOT siemens DOT ru>
To: <cygwin AT sourceware DOT cygnus DOT com>
Subject: Sorry, resent RE: Accessing exported variables in DLL with dlsym().
Date: Thu, 6 Jul 2000 13:07:05 +0400
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(Sorry, I clicked wong button)

>
> I am trying to port a program that opens dynamic library with
> dlopen() and looks up symbol with dlsym(). This works for
> function reference but not for variable. The porgram is:
>
> main.c:
>
> #include <dlfcn.h>
> #include <stdio.h>
>
> main() {
>     int (*foo)(void);
>     void *libfoo;
>
>     libfoo = dlopen ("libfoo.dll", 0);
>     foo = dlsym (libfoo, "foo");
>     foo();
> }
>
> foo.c:
>
> #include <stdio.h>
> #include <dlfcn.h>
>
> __declspec (dllexport) extern foo (void);
>
> foo() {
>     char *bar;
>     void *libbar;
>
>     libbar = dlopen ("libbar.dll", 0);
>     bar = dlsym (libbar, "bar");
>     puts (bar);
> }

... continued ...

bar.c:

__declspec (dllexport) char *bar = "Hi! I am bar.";

Compiled with:

gcc -c main.c foo.c bar.c
dllwrap --output-exp libfoo.exp --output-lib libfoo.a  --output-def
libfoo.def --dllname libfool --export-all-symbols foo.o
dllwrap --output-exp libbar.exp --output-lib libbar.a  --output-def
libbar.def --dllname libbar.dll --export-all-symbols bar.o
gcc -o main main.o

Unfortunately, this program prints nothing (that is, bar appears to be
found - but porbably points to wrong location).  IF I bind foo.o with
libbar.a (and declare bar in foo.c as dllimport) I get correct result.
The foo() in main() is correctly found.

TIA

-andrej


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