Jean Brouwers added the comment:
Attached is an updated dlibtest.c file. It prints a message in the con-
/destructor functions and if that fails it calls _exit(9).
Compile and run it as before and check the exit status. If the latter
is 9 or 011, a printf error occurred indicating e.g. that stdout was
closed or something similar.
This version can also be used with gdb, either by pre-loading the
dlibtest.so library within gdb or before invoking gdb. To preload the
library within gdb (on Linux) use
gdb .../python
(gdb) set environment LD_PRELOAD ./dlibtest.so
(gdb) run
.....
or to preload before gdb use
setenv LD_PRELOAD ./dlibtest.so
gdb .../python
(gdb) run
.....
Lastly, my previous observations about this issue were clearly a "trompe
d'oeil", especially my statement that PyImport_Cleanup never returned.
The missing print statements *after* the PyImport_Cleanup call are
simply due to printf errors, and nothing else ;-)
Added file: http://bugs.python.org/file8625/dlibtest.c
__________________________________
Tracker <[EMAIL PROTECTED]>
<http://bugs.python.org/issue1329>
__________________________________
#include "stdio.h"
#include "string.h"
#include "unistd.h"
#ifndef __GNUC__
# error requires the GNU compiler
#endif
extern const char* __progname;
/* call printf() only if inside python binary */
static void
_printf (const char* fmt, const char* arg1, const char* arg2)
{
if (!strcmp("python", __progname)) {
if (printf(fmt, arg1, arg2) < 0) {
_exit(9); /* stdout closed? */
}
}
}
#if 0 /* pick this ... */
static void __attribute__((constructor)) /* called on main() */
_ctor (void)
{
_printf("*** %s called in %s ...\n", "ctor", __progname);
}
static void __attribute__((destructor)) /* called on exit() */
_dtor (void)
{
_printf("*** %s called in %s ...\n", "dtor", __progname);
}
#else /* ... or this case */
static void /* called on Python exit */
_dtor (void)
{
_printf("*** %s called in %s ...\n", "dtor", __progname);
}
/* the weak attribute prevents unresolved symbol errors */
extern int Py_AtExit (void(*func)(void)) __attribute__((weak));
static void __attribute__((constructor)) /* called on main() */
_ctor (void)
{
_printf("*** %s called in %s ...\n", "ctor", __progname);
if (Py_AtExit) {
_printf("*** %s %s\n", "Py_AtExit", (Py_AtExit(_dtor) < 0 ? "failed!" :
"OK"));
}
}
#endif
/* =====================================================
Build this file into a shared library, then pre-load
that library with the Python binary as follows.
On Linux, compile as
gcc -o dlibtest.os -c -m32 -Wall -Werror -fPIC dlibtest.c
gcc -o dlibtest.so -m32 -ldl -shared dlibtest.os
and then run
env LD_PRELOAD=./dlibtest.so .../python
On MacOS X, compile as
gcc -o dlibtest.os -c -Wall -Werror -march=i686 -fPIC dlibtest.c
gcc -o dlibtest.dylib -undefined dynamic_lookup -lpthread -dynamiclib
dlibtest.os
and run
env DYLD_INSERT_LIBRARIES=./dlibtest.dylib .../python.exe
To preload the library within gdb (on Linux) use
gdb .../python
(gdb) set environment LD_PRELOAD ./dlibtest.so
(gdb) run
.....
or use
setenv LD_PRELOAD ./dlibtest.so
gdb .../python
(gdb) run
.....
After Ctrl-D two messages should have been printed, but 3.0a1
prints only the first one. An exist status is 9 or 011 indicates
that a printf error occurred.
Here is a log from Linux with my 3.0a1 and 2.51 builds and
with 2.3.4 included with the Linux distro:
$ gcc -o dlibtest.os -c -m32 -Wall -Werror -fPIC dlibtest.c
$ gcc -o dlibtest.so -m32 -ldl -shared dlibtest.os
$ env LD_PRELOAD=./dlibtest.so ~/Python-3.0a1/python
*** ctor called ...
Python 3.0a1 (py3k, Oct 26 2007, 09:45:17)
[GCC 3.4.6 20060404 (Red Hat 3.4.6-8)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>
$ env LD_PRELOAD=./dlibtest.so ~/Python-2.5.1/python
*** ctor called ...
Python 2.5.1 (r251:54863, Oct 22 2007, 16:19:11)
[GCC 3.4.6 20060404 (Red Hat 3.4.6-8)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>
*** dtor called ...
$ env LD_PRELOAD=./dlibtest.so /usr/bin/python
*** ctor called ...
Python 2.3.4 (#1, May 2 2007, 19:26:00)
[GCC 3.4.6 20060404 (Red Hat 3.4.6-8)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>
*** dtor called ...
Similarly on MacOS X with Python 2.3.5 distributed by Apple:
% env DYLD_INSERT_LIBRARIES=./dlibtest.dylib ~/Python-3.0a1/python.exe
*** ctor called ...
Python 3.0a1 (py3k, Oct 25 2007, 14:55:57)
[GCC 4.0.1 (Apple Computer, Inc. build 5367)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> ^D
% env DYLD_INSERT_LIBRARIES=./dlibtest.dylib ~/Python-2.5.1/python.exe
*** ctor called ...
Python 2.5.1 (r251:54863, Oct 22 2007, 16:18:08)
[GCC 4.0.1 (Apple Computer, Inc. build 5341)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> ^D
*** dtor called ...
% env DYLD_INSERT_LIBRARIES=./dlibtest.dylib /usr/bin/python
*** ctor called ...
Python 2.3.5 (#1, Jan 13 2006, 20:13:11)
[GCC 4.0.1 (Apple Computer, Inc. build 5250)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> ^D
*** dtor called ...
/Jean Brouwers <[EMAIL PROTECTED]>
PS) For more details on the con/destructor attributes, see the GNU
gcc documentation at
<http://gcc.gnu.org/onlinedocs/gcc-3.2/gcc/Function-Attributes.html>
See also Apple's documentation DynamicLibrary.pdf which
contains some excellent examples plus special MacOS X
features. E.g. c/dtor must be ZPRIVATE and a static
ctor can have main-like argc, argv and envp arguments!
===================================================== */
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