call init function when *loading* dynamic shared libraries?

• Subject: call init function when *loading* dynamic shared libraries?
• From: Dimitri Papadopoulos-Orfanos <email@hidden>
• Date: Wed, 12 Feb 2003 16:15:19 +0100
• User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3a) Gecko/20021212

Hi,

I'm programming in C++ for Mac OS X 10.2.2. I'm using December 2002 Mac
OS X Developer Tools.

I would like the constructors of static instances of classes to be
called automatically when a dynamic shared library is *loaded* into a
program. Not when a symbol is used from the library. I can't get it to work.

Actually I've even tried with a simple C program and a function
specified with the -init option flag. This function is not called upon
loading the dynamic shared library - only when the first symbol is
used from the library.

The -bind_at_load option flag doesn't help either.

Here is the source code of the libfoo.dylib shared dynamic library:

	#include <stdio.h>

	void library_init() {
	  printf("library_init()\n");
	}

	void use_library_symbol() {
	  printf("use_library_symbol()\n");
	}

Here is how I build it:
	gcc -o libfoo.dylib -dynamiclib -bind_at_load \
		-init _library_init foo.c

Here is the source of the a.out main program:

	extern void use_library_symbol();

	int main() {
	  /* use_library_symbol(); */
	  return 0;
	}

Here is how I build it:
	gcc main.c -L. -lfoo

Here is what happens when I run it:
	$ ./a.out
	$

Now if I uncomment the commented line so that a library symbol is used:
	$ ./a.out
	library_init()
	use_library_symbol()
	$

Is there any way to get intialization routines called when *loading* a
dynamic shared library? Am I maybe doing anything wrong when linking the
library or the program?

Regards,
--
Dimitri
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