Apache 2 loadable module fails to parse directive - apache

Question

I have an Apache 2.2 loadable module which is not handling directive processing correctly.
The module originally used a static configuration but now uses per-server allocation using a server configuration routine declared in the AP_MODULE_DECLARE_DATA. I've confirmed that the operational routines are mapping the configuration data correctly.
Everything works correctly when there is no TD_LOGDEBUG directive in the httpd.conf.
When there is a TD_LOGDEBUG directive, on entry to the "static const char *logdebug_cfg", it appears that the module config pointer "mconfig" in the call is null. If the pointer is taken as valid, the module segfaults at server start time. Debugging has been difficult due to the lack of server or request context at this point to produce Apache log messages.
Adding a conditional "if (scfg) {" around the directive parsing code (as seen at the Apache modules site) eliminates the segfault but it also apparently stops the parsing and storage from occurring. At runtime I see in the log:
mod_demotest: demotest - logdebug = 0x00078000
which is the value inserted at server configuration, rather than the expected 0x00000003 due to the "TD_LOGDEBUG 0x3" directive in httpd.conf
Again, this was all working code in the static-configuration original. The only mods to the code were for per-server configuration.
The code below has been cut down from the original module to the minimum which shows the problem.
I'd be grateful if anyone can offer insight into the issue.
#include "httpd.h"
#include "http_config.h"
#include "http_request.h"
#include "http_protocol.h"
#include "http_core.h"
#include "http_main.h"
#include "http_log.h"
#include "ap_mpm.h"
#include "apr_strings.h"
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <arpa/inet.h>
#include <netdb.h>
#define MODULE_NAME "mod_demotest"
#define MODULE_VERSION "2.0.1" /* Module revision level */
module AP_MODULE_DECLARE_DATA demotest_module;
static int demotest_handler(request_rec *r);
static int demotest_post_config(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *ptemp, server_rec *s);
typedef struct {
unsigned long logdebug;
} mod_config;
static void str_to_lower(char *string) {
while (*string) {
if ( (*string >= 'A') && (*string <= 'Z') ) *string = *string + 32;
string++;
}
}
unsigned long htoi(char *ptr) {
unsigned long value = 0;
char ch = *ptr;
str_to_lower(ptr);
while ( (ch == '0') || (ch == 'x') ) ch = *(++ptr);
while ( ( (ch >= '0') && (ch <= '9') ) || ( (ch >= 'a') && (ch <= 'f') ) ) {
if (ch >= '0' && ch <= '9')
value = (value << 4) + (ch - '0');
if (ch >= 'a' && ch <= 'f')
value = (value << 4) + (ch - 'a' + 10);
ch = *(++ptr);
}
return value;
}
static int demotest_handler
(request_rec *r) {
mod_config *scfg = ap_get_module_config(r->server->module_config,
&demotest_module);
ap_log_rerror(APLOG_MARK, APLOG_CRIT, 0, r,
"mod_demotest: demotest - logdebug = 0x%08x",
scfg->logdebug);
return DECLINED;
}
static const char *logdebug_cfg
(cmd_parms *parms, void *mconfig, const char *arg) {
mod_config *scfg = (mod_config *)mconfig;
if (scfg) {
scfg->logdebug = htoi((char *)arg);
}
return NULL;
}
static void *demotest_server_config
(apr_pool_t *p, server_rec *s) {
mod_config *scfg;
scfg = apr_palloc(p, sizeof(*scfg));
scfg->logdebug = 0x78000;
return (void *)scfg;
}
static int demotest_post_config
(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *ptemp, server_rec *s) {
const char *userdata_key = "demotest_init";
void *data = NULL;
apr_pool_userdata_get(&data, userdata_key, s->process->pool);
if (data == NULL) {
apr_pool_userdata_set((const void *)1, userdata_key,
apr_pool_cleanup_null, s->process->pool);
return OK;
}
ap_log_error(APLOG_MARK, APLOG_CRIT, 0, s,
MODULE_NAME " " MODULE_VERSION " started");
return OK;
}
static void register_hooks(apr_pool_t *p) {
ap_hook_post_config(demotest_post_config, NULL, NULL, APR_HOOK_MIDDLE);
ap_hook_access_checker(demotest_handler, NULL, NULL, APR_HOOK_MIDDLE);
}
static command_rec demotest_directives[] = {
AP_INIT_TAKE1("TD_LogDebug", logdebug_cfg, NULL, RSRC_CONF,
"Log internal trace/debug info. Default: 0x0000 = none"),
{NULL}
};
module AP_MODULE_DECLARE_DATA demotest_module = {
STANDARD20_MODULE_STUFF,
NULL, /* create per-dir config structures */
NULL, /* merge per-dir config structures */
demotest_server_config, /* create per-server config structures */
NULL, /* merge per-server config structures */
demotest_directives, /* table of config file commands */
register_hooks
};

Answer 1

Problem solved. The Apache Project example for this situation is strikingly incorrect. mconfig is not a pointer to the module configuration; it is always NULL at the call.
The resolution is shown below.
static const char *logdebug_cfg
(cmd_parms *parms, void *mconfig, const char *arg) {
/* Retrieve the per-server configuration */
mod_config *scfg = ap_get_module_config(parms->server->module_config, &torcheck_module);
scfg->logdebug = htoi((char *)arg);
return NULL;