You are a few weeks too late. :-)
See:
http://issues.apache.org/jira/browse/MODPYTHON-98
There are whole bunch of little issues with adding handlers using
req.add_handler(). For this one you seem to have tread much the
same path as I did.
Graham
Joseph Barillari wrote ..
> Hi,
>
> So far, I really like mod_python -- it's a great piece of
> software. But I think I've found a small bug.
>
> I've noticed that adding a handler using add_handler prompts apache to
> segfault if no statically registered (e.g., specified in the apache
> conf files) handlers of the same category (e.g., PythonLogHandler,
> PythonTransHandler) are present. I've tested this in both the release
> version (314) and version 325b (albeit more thoroughly in the former).
>
> Here's how I triggered the bug:
>
> Add this to apache2.conf:
> PythonPath "sys.path+[(the path goes here)]"
> PythonTransHandler crashbug
>
> crashbug.py contains:
>
> from mod_python import apache
>
> def transhandler(req):
> req.add_handler("PythonLogHandler","foo::loghandler")
> return apache.OK
>
> foo contains:
>
> from mod_python import apache
>
> def loghandler(req):
> import sys
> sys.stderr.write("foo: saw request type:" + req.method + "\n")
> return apache.OK
>
> If I run apache
>
> sudo /usr/sbin/apache2 -X
>
> and tickle the server:
>
> echo -e "GET / HTTP/1.0\n\n" | nc localhost 8080
>
> ...apache segfaults.
>
> On the other hand, if I add the line
>
> PythonLogHandler notfoo
>
> to apache2.conf, where notfoo.py is identical to foo except that
> "foo:" is replaced with "notfoo", I get the expected two lines in the
> log, and no crash.
>
> Here's the trace:
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread -1214269216 (LWP 21283)]
> 0xb76dddb3 in hlist_copy (p=0x8158fa8, hle=0x0) at hlist.c:91
> 91 head->handler = apr_pstrdup(p, hle->handler);
> (gdb) bt
> #0 0xb76dddb3 in hlist_copy (p=0x8158fa8, hle=0x0) at hlist.c:91
> #1 0xb76dd9aa in MpHList_FromHLEntry (hle=0x0) at hlistobject.c:49
> #2 0xb76e59b6 in python_handler (req=0x8238480, phase=0xb76e804c
> "PythonLogHandler")
> at mod_python.c:1029
> #3 0x08086086 in ap_run_log_transaction ()
> #4 0x0806963e in ap_process_request ()
> #5 0x08064b19 in _start ()
>
>
> I suspect the problem is in this part of mod_python.c:
>
> Here's my understanding (please correct me if I'm wrong). If hle is
> NULL (i.e., there were no handlers of this type registered in the
> apache conf), but dynhle is not null (we registered a dynamic
> handler), we continue processing...
>
> if (! (hle || dynhle)) {
> /* nothing to do here */
> return DECLINED;
> }
>
> /* determine interpreter to use */
> interp_name = select_interp_name(req, NULL, conf, hle, NULL, 0);
>
> /* get/create interpreter */
> idata = get_interpreter(interp_name, req->server);
>
> if (!idata)
> return HTTP_INTERNAL_SERVER_ERROR;
>
> /* create/acquire request object */
> request_obj = get_request_object(req, interp_name, phase);
>
> /* remember the extension if any. used by publisher */
> if (ext)
> request_obj->extension = apr_pstrdup(req->pool, ext);
>
> But then, we try to create an MpHList from hle, which is NULL -- prompting
> a crash a few levels down.
>
> /* create a hahdler list object */
> request_obj->hlo = (hlistobject *)MpHList_FromHLEntry(hle);
>
>
> Here's how I fixed it:
>
> --- /home/jdb/dl/mpsvn/mod_python-3.1.4/src/mod_python.c 2005-01-29
> 16:25:28.0
> -0500
> +++ mod_python.c 2006-01-04 16:59:13.0 -0500
> @@ -1026,13 +1026,18 @@
> request_obj->extension = apr_pstrdup(req->pool, ext);
>
> /* create a hahdler list object */
> -request_obj->hlo = (hlistobject *)MpHList_FromHLEntry(hle);
> -
> -/* add dynamically registered handlers, if any */
> -if (dynhle) {
> +if (hle) {
> + request_obj->hlo = (hlistobject *)MpHList_FromHLEntry(hle);
> + /* add dynamically registered handlers, if any */
> + if (dynhle) {
> MpHList_Append(request_obj->hlo, dynhle);
> + }
> }
> -
> +else {
> + /* hle was NULL; so create hlo from dynhle */
> + request_obj->hlo = (hlistobject *)MpHList_FromHLEntry(dynhle);
> +}
> +
> /*
> * Here is where we call into Python!
> * This is the C equivalent of
>
> AFAIK, this works -- but I'm new at this.
>
> best regards,
>
> Joe
