My thanks to everyone for their input on this problem. While I was unable to
get the backtrace and whatkilledus modules to report on failure, I isolated the
cause to the following code in the handler.
The code itself does not segfault and indeed it appears to execute properly,
retrieving the user-agent string with correct length and logging it. However,
when this code is included Apache segfaults some time later. (It's not the
logging causing it; the segfault still occurs without the logging.)
I can not see why this code should be overwriting Apache data structures in
such a way as to cause Apache to segfault. I have rewritten it several
different ways and it still causes segfaults.
Might anyone have insight into this issue?
== HANDLER CODE ==
static int bridcheck_handler
(request_rec *r) {
const char *ua_pointer;
char useragent[UA_BUFFERSIZE];
size_t ualength;
size_t ualen2;
/* Retrieve the user-agent string */
/* Null the last byte in our buffer so that strings are always terminated
*/
useragent[UA_BUFFERSIZE-1] = '\0';
/* Load pointer to the Apache request record user-agent header field */
ua_pointer = apr_table_get(r->headers_in, "User-Agent");
/* Find out how long the Apache-supplied string is */
ualength = strlen(ua_pointer);
/* Copy only if there's something to copy */
if (ualength != 0)
/* Our buffer gets Apache's request record user-agent field */
/* Protect from segfault by limiting length at buffersize -1 */
strncpy(useragent, ua_pointer, UA_BUFFERSIZE-1);
/* Don't use the original strncpy below. Dissected the functionality
into pieces above. */
/* strncpy(useragent, apr_table_get(r->headers_in, "User-Agent"),
UA_BUFFERSIZE-1); */
/* Now that we have our prize ... how long is it? */
ualen2 = strlen(useragent);
ap_log_rerror(APLOG_MARK, APLOG_NOTICE, 0, r,
"bc: ualength = %u, <%s>",
ualength, apr_table_get(r->headers_in, "User-Agent"));
ap_log_rerror(APLOG_MARK, APLOG_NOTICE, 0, r,
"ualen2 = %u, <%s>",
ualen2, useragent);
return DECLINED;
}
== ERROR LOG EXTRACT
Oct 26 05:10:39 157.55.39.67 bc: ualength = 71, http://www.bing.com/bingbot.htm)>
Oct 26 05:10:39 157.55.39.67 ualen2 = 71, http://www.bing.com/bingbot.htm)>
Oct 26 05:11:11 71.6.232.7 bc: ualength = 115,
Oct 26 05:11:11 71.6.232.7 ualen2 = 115,
Oct 26 05:17:33 110.70.47.92 bc: ualength = 120,
Oct 26 05:17:33 110.70.47.92 ualen2 = 120,
