[bug-libextractor] Re: ports/88716: [patch] fix textproc/libextractor double free() bug

[Vasil Dimov]

On Wed, Nov 09, 2005 at 12:53:05PM -0800, Christian Grothoff wrote:
> Patch looks good and will be in the next LE release (is already in subversion 
> 2237).  I'm still not sure under which circumstances the _destructor_ 
> function is invoked twice without _constructor_ in the meantime (BSD-ism?) 

The constructor and the destructor are called 3 times each:

$ ./.libs/lt-trivialtest
// constructor call 1, does not initialize old_dlsearchpath
extractor.c:215 le_ltdl_init begin old_dlsearchpath=0x0
extractor.c:246 le_ltdl_init end old_dlsearchpath=0x0

trivialtest.c:23 main begin

// constructor call 2, initializes old_dlsearchpath
extractor.c:215 le_ltdl_init begin old_dlsearchpath=0x0
extractor.c:246 le_ltdl_init end old_dlsearchpath=0x501280

// destructor call 1, frees old_dlsearchpath
extractor.c:250 le_ltdl_fini begin old_dlsearchpath=0x501280
extractor.c:253 le_ltdl_fini free(0x501280)
extractor.c:262 le_ltdl_fini end old_dlsearchpath=0x501280

// constructor call 3, initializes old_dlsearchpath (again)
extractor.c:215 le_ltdl_init begin old_dlsearchpath=0x501280
extractor.c:246 le_ltdl_init end old_dlsearchpath=0x5012c0

// destructor call 2, frees old_dlsearchpath,
// initialized from constructor call 3
extractor.c:250 le_ltdl_fini begin old_dlsearchpath=0x5012c0
extractor.c:253 le_ltdl_fini free(0x5012c0)
extractor.c:262 le_ltdl_fini end old_dlsearchpath=0x5012c0

trivialtest.c:27 main end

// destructor call 3, attempts to free old_dlsearchpath, initialized
// from constructor call 3
extractor.c:250 le_ltdl_fini begin old_dlsearchpath=0x5012c0
extractor.c:253 le_ltdl_fini free(0x5012c0)
lt-trivialtest in free(): error: chunk is already free
Abort trap: 6 (core dumped)
$

Lets see what happens on Linux:

$ uname -a
Linux fqdn 2.4.18-14 #1 Wed Sep 4 13:35:50 EDT 2002 i686 i686 i386 GNU/Linux

$ /lib/libc.so.6
GNU C Library development release version 2.2.93, by Roland McGrath et al.
Copyright (C) 1992-2001, 2002 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 3.2 20020903 (Red Hat Linux 8.0 3.2-7).
Compiled on a Linux 2.4.9-9 system on 2002-09-05.
Available extensions:
        GNU libio by Per Bothner
        crypt add-on version 2.1 by Michael Glad and others
        The C stubs add-on version 2.1.2.
        linuxthreads-0.10 by Xavier Leroy
        BIND-8.2.3-T5B
        NIS(YP)/NIS+ NSS modules 0.19 by Thorsten Kukuk
        Glibc-2.0 compatibility add-on by Cristian Gafton
        libthread_db work sponsored by Alpha Processor Inc
Report bugs using the `glibcbug' script to <address@hidden>.

$ gcc --version
gcc (GCC) 3.2 20020903 (Red Hat Linux 8.0 3.2-7)
...

$ ./.libs/lt-trivialtest
extractor.c:215 le_ltdl_init begin old_dlsearchpath=(nil)
extractor.c:246 le_ltdl_init end old_dlsearchpath=(nil)
trivialtest.c:23 main begin
trivialtest.c:27 main end
extractor.c:250 le_ltdl_fini begin old_dlsearchpath=(nil)
extractor.c:262 le_ltdl_fini end old_dlsearchpath=(nil)
$

Hmmz, looks quite different.

-- 
Vasil Dimov

pgptxubBfm1oV.pgp
Description: PGP signature