From mboxrd@z Thu Jan  1 00:00:00 1970
From: hjl@lucon.org (H.J. Lu)
To: drepper@cygnus.com (Ulrich Drepper)
Cc: egcs@cygnus.com, libc-hacker@gnu.org (GNU C Library)
Subject: A problem with shared library and libgcc.a
Date: Wed, 29 Apr 1998 18:36:00 -0000
Message-id: <m0yUhRj-000268C@ocean.lucon.org>
X-SW-Source: 1998-04/msg01173.html

Hi,

I think I figured out why gcc -shared doesn't with glibc 2.1 if dlopen
is used by the static executable.

The problem is with gcc -shared including -lgcc. When we build libfoo.so
with

# gcc -shared -o libfoo.so

It includes -lgcc -lc. As the result

# ldd libfoo.so
        libc.so.6 => /opt/glibc-2/lib/libc.so.6 (0x40007000)
	/opt/glibc-2/lib/ld-linux.so.2 => /opt/glibc-2/lib/ld-linux.so.2 (0x00000000)

When dlopen () is called, libfoo.so and libc.so.6 are loaded, libfoo.so
first and followed by libc.so.6. Since __register_frame_info and
__deregister_frame_info from libgcc.a are in libfoo.so, libc.so.6
also uses the same __register_frame_info and __deregister_frame_info
in libfoo.so. When dlclose is called, libfoo.so is munmapped first.
When libc.so.6 is removed from memory, __deregister_frame_info is
called. But now __deregister_frame_info in libfoo.so is no longer
in memory. We get a problem.

I don't know what the best solution is. But it should be fixed.

Thanks.


-- 
H.J. Lu (hjl@gnu.org)