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http://issues.apache.org/jira/browse/MODPYTHON-187?page=comments#action_12431107
]
Jim Gallacher commented on MODPYTHON-187:
-----------------------------------------
The problem seems to be in the tableobject.c function table_subscript().
subprocess_env.get['SCRIPT_FILENAME'] is being evaluated in the post read
request phase. It would seem that req.add_common_vars adds a key for
SCRIPT_FILENAME to the table, but since the filename has not been translated
yet its value is NULL.
table_subscript() retrieves the value with the following bit of code:
while (i--)
if (elts[i].key) {
if (apr_strnatcasecmp(elts[i].key, k) == 0) {
PyObject *v = PyString_FromString(elts[i].val);
PyList_Insert(list, 0, v);
Py_DECREF(v);
}
}
The problem is with the PyString_FromString. According to the python docs, the
parameter passed must not be NULL and it will not be checked. I assume this is
the origin of the segfault.
Something like the following seems to fix the problem.
The following code snippet seems to fix the problem, and is attached as
MP187-2006-08-28-jgallacher-1.diff. Am I correct in doing the PY_INCREF(v)??
while (i--)
if (elts[i].key) {
if (apr_strnatcasecmp(elts[i].key, k) == 0) {
- PyObject *v = PyString_FromString(elts[i].val);
+ PyObject *v = NULL;
+ if (elts[i].val != NULL) {
+ v = PyString_FromString(elts[i].val);
+ } else {
+ v = Py_None;
+ Py_INCREF(v);
+ }
PyList_Insert(list, 0, v);
Py_DECREF(v);
> Hang on subscripted access to request.subprocess_env.
> -----------------------------------------------------
>
> Key: MODPYTHON-187
> URL: http://issues.apache.org/jira/browse/MODPYTHON-187
> Project: mod_python
> Issue Type: Bug
> Components: core
> Affects Versions: 3.2.10
> Environment: Apache: 2.0.59
> ModPython: 3.2.10
> Python: 2.4
> OS: Windows Server 2003
> Reporter: Alan Kennedy
>
> When subscripted access is used to access variable 'SCRIPT_FILENAME' in the
> request.subprocess_env table/mapping, the code hangs.
> The following snippet illustrates the problem.
> # -=-=-=-=-=-=
> def postreadrequesthandler(request):
> request.add_common_vars()
> value = request.subprocess_env['SCRIPT_FILENAME'] # This hangs
> # value = request.subprocess_env.get('SCRIPT_FILENAME')# This works
> return apache.OK
> # -=-=-=-=-=-=
> The strange thing is that the .get() access works fine: only the subscript
> hangs?
> If anyone is wondering about a use-case, I don't actually have one. I was
> just iterating over the contents of the request.subprocess_env using a for
> loop (code below), and found that the code hung when accessing
> 'SCRIPT_FILENAME', and not for any other variable.
> # -=-=-=
> request.add_common_vars()
> d = {}
> for sek in request.subprocess_env.keys():
> d[sek] = request.subprocess_env[sek]
> # -=-=-=
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