New submission from Graham Dumpleton <[EMAIL PROTECTED]>:
Somewhere between Python 3.0a3 and Python 3.0b3, a call to PySys_SetObject()
after having used Py_NewInterpreter() to create a sub interpreter causes a
crash. This appears to be due to interp->sysdict being NULL after
Py_NewInterpreter() called.
As illustration of problem, consider program for Python 2.X.
#include <Python.h>
int
main(int argc, char *argv[])
{
Py_Initialize();
PySys_SetObject("xxx", PyLong_FromLongLong(1));
fprintf(stderr, "sysdict=%d\n", !!PyThreadState_Get()->interp->sysdict);
fflush(stderr);
PyRun_SimpleString("import sys\n"
"print >> sys.stderr, 'xxx =', sys.xxx\n");
Py_NewInterpreter();
fprintf(stderr, "sysdict=%d\n", !!PyThreadState_Get()->interp->sysdict);
fflush(stderr);
PySys_SetObject("yyy", PyLong_FromLongLong(2));
PyRun_SimpleString("import sys\n"
"print >> sys.stderr, 'yyy =', sys.yyy\n");
Py_Finalize();
return 0;
}
This when run yields:
sysdict=1
xxx = 1
sysdict=1
yyy = 2
Now, for Python 3.0 variant of same program:
#include <Python.h>
int
main(int argc, char *argv[])
{
Py_Initialize();
fprintf(stderr, "sysdict=%d\n", !!PyThreadState_Get()->interp->sysdict);
fflush(stderr);
PySys_SetObject("xxx", PyLong_FromLongLong(1));
PyRun_SimpleString("import sys\n"
"print('xxx =',sys.xxx, file=sys.stderr)\n");
Py_NewInterpreter();
fprintf(stderr, "sysdict=%d\n", !!PyThreadState_Get()->interp->sysdict);
fflush(stderr);
PySys_SetObject("yyy", PyLong_FromLongLong(2));
PyRun_SimpleString("import sys\n"
"print('yyy =',sys.yyy, file=sys.stderr)\n");
Py_Finalize();
return 0;
}
I get for Python 3.0a3:
sysdict=1
xxx = 1
sysdict=1
object : AttributeError("'module' object has no attribute 'stderr'",)
type : AttributeError
refcount: 4
address : 0xf1180
lost sys.stderr
I am not concerned here about loss of sys.stderr, although that could be a
separate issue for all I know.
The important bit here is that sysdict is set after Py_NewInterpreter().
In Python 3.0b3/3.0rc1 I instead get:
sysdict=1
xxx = 1
sysdict=0
Bus error
This is because PySys_SetObject() is presumably crashing because sysdict is
not set in interp object.
I tried to ask about this on python-3000 Google group, but that message ended
up in some moderation queue and has vanished. Thus quote part of that message
below.
"""
>From what I can tell so far the problem is that 'interp->sysdict' is
NULL after calling Py_NewInterpreter() to create a secondary sub
interpreter.
Reading through code and using a debugger, at this point this seems to
be due to condition if code:
sysmod = _PyImport_FindExtension("sys", "sys");
if (bimod != NULL && sysmod != NULL) {
interp->sysdict = PyModule_GetDict(sysmod);
if (interp->sysdict == NULL)
goto handle_error;
Py_INCREF(interp->sysdict);
PySys_SetPath(Py_GetPath());
PyDict_SetItemString(interp->sysdict, "modules",
interp->modules);
_PyImportHooks_Init();
initmain();
if (!Py_NoSiteFlag)
initsite();
}
in Py_NewInterpreter() not executing due to
_PyImport_FindExtension("sys", "sys") returning NULL.
Down in _PyImport_FindExtension(), it appears that the reason it fails
is because of following returning with NULL.
def = (PyModuleDef*)PyDict_GetItemString(extensions,
filename);
.....
if (def->m_base.m_init == NULL)
return NULL;
In other words, whatever m_base.m_init is meant to be is NULL when
perhaps it isn't meant to be.
(gdb) call ((PyModuleDef*)PyDict_GetItemString(extensions,"builtins"))-
>m_base.m_init
$9 = (PyObject *(*)()) 0
(gdb) call ((PyModuleDef*)PyDict_GetItemString(extensions,"sys"))-
>m_base.m_init
$10 = (PyObject *(*)()) 0
I am going to keep tracking through to try and work out why, but
posting this initial information in case this rings a bell with
anyone.
"""
Is this expected behaviour? Or, is it necessary now to perform some special
initialisation after having called Py_NewInterpreter() to get builtins and
sys modules setup?
This problem originally came up with mod_wsgi, which worked fine with Python
3.0a3, but fails on more recent releases because of this.
I know sub interpreters may be seen as evil by some and the target of
removal, but are they still meant to work for now at least?
----------
components: Interpreter Core
messages: 73483
nosy: grahamd
severity: normal
status: open
title: PySys_SetObject crashes after Py_NewInterpreter().
versions: Python 3.0
_______________________________________
Python tracker <[EMAIL PROTECTED]>
<http://bugs.python.org/issue3919>
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