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Date: Mon, 13 May 1996 00:50:13 -0400 (EDT)
From: Chuck Robey <chuckr@Glue.umd.edu>
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To: FreeBSD Ports <FreeBSD-Ports@FreeBSD.ORG>
Subject: dynamic linking
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One more time, in case you missed it.  If I don't get an answer this 
time, I'll stop bugging you.  I am working on getting the tcl code to 
dynamically load modules, and to do that I'm trying to understand the 
dlopen/dlsym calls.  I wrote a very simple program to test it, which just 
takes a file from the command line and dloads it.  To use a file I knew 
was in correct format, I used one from libc, but I always get this kind 
of error:

./dltests /usr/obj/lib/libc/rmdir.so
testing file /usr/obj/lib/libc/rmdir.so ... dlopen call returned pointer 
value 0
dlerror call returns mmap failed for "/usr/obj/lib/libc/rmdir.so" : 
Invalid argument

OK, below is the code I wrote to test it.  Anyone got any idea why it's 
failing?

Thanks.

#include <stdio.h>
#include <dlfcn.h>

void main( int argc, char *argv[] )
{
	int err_ret;
	void *pntr;

	if( argc != 2 )
	{
		printf("%s: incorrect number of parameters.\n",argv[0]);
		printf("\tInvoke as: %s <object file to open>\n",argv[0]);
		exit(0);
	}
	printf("testing file %s ... ", argv[1]);
	pntr = dlopen( argv[1], 1 );
	printf("dlopen call returned pointer value %lx\n", pntr );
	printf("dlerror call returns %s\n", dlerror() );
	if( pntr )
	{
		err_ret = dlclose( pntr );
		printf("since open was successful, dlclose returns %d\n",
			err_ret );
		printf("and subsequent dlerror call returns %s\n",dlerror());
	}
	exit(0);
}


==========================================================================
Chuck Robey chuckr@eng.umd.edu, I run FreeBSD-current on n3lxx + Journey2
 
Three Accounts for the Super-users in the sky,
  Seven for the Operators in their halls of fame,
Nine for Ordinary Users doomed to crie,
  One for the Illegal Cracker with his evil game
In the Domains of Internet where the data lie.
  One Account to rule them all, One Account to watch them,
  One Account to make them all and in the network bind them.