Ad-hoc backtrace logging with isc_backtrace_log()

It's sometimes helpful to get a quick idea of the call stack when
debugging. This change factors out the backtrace logging from named's
fatal error handler so that it's easy to use in other places too.

Author: fanf2

bin/named/main.c

@@ -101,13 +101,6 @@
  */
 /* #include "xxdb.h" */
 
-/*
- * The maximum number of stack frames to dump on assertion failure.
- */
-#ifndef BACKTRACE_MAXFRAME
-#define BACKTRACE_MAXFRAME 128
-#endif /* ifndef BACKTRACE_MAXFRAME */
-
 extern unsigned int dns_zone_mkey_hour;
 extern unsigned int dns_zone_mkey_day;
 extern unsigned int dns_zone_mkey_month;
@@ -189,9 +182,6 @@ assertion_failed(const char *file, int line, isc_assertiontype_t type,
 static void
 assertion_failed(const char *file, int line, isc_assertiontype_t type,
 		 const char *cond) {
-	void *tracebuf[BACKTRACE_MAXFRAME];
-	int nframes;
-
 	/*
 	 * Handle assertion failures.
 	 */
@@ -203,24 +193,12 @@ assertion_failed(const char *file, int line, isc_assertiontype_t type,
 		 */
 		isc_assertion_setcallback(NULL);
 
-		nframes = isc_backtrace(tracebuf, BACKTRACE_MAXFRAME);
 		isc_log_write(named_g_lctx, NAMED_LOGCATEGORY_GENERAL,
 			      NAMED_LOGMODULE_MAIN, ISC_LOG_CRITICAL,
-			      "%s:%d: %s(%s) failed%s", file, line,
-			      isc_assertion_typetotext(type), cond,
-			      (nframes > 0) ? ", back trace" : "");
-		if (nframes > 0) {
-			char **strs = isc_backtrace_symbols(tracebuf, nframes);
-			if (strs != NULL) {
-				for (int i = 0; i < nframes; i++) {
-					isc_log_write(named_g_lctx,
-						      NAMED_LOGCATEGORY_GENERAL,
-						      NAMED_LOGMODULE_MAIN,
-						      ISC_LOG_CRITICAL, "%s",
-						      strs[i]);
-				}
-			}
-		}
+			      "%s:%d: %s(%s) failed", file, line,
+			      isc_assertion_typetotext(type), cond);
+		isc_backtrace_log(named_g_lctx, NAMED_LOGCATEGORY_GENERAL,
+				  NAMED_LOGMODULE_MAIN, ISC_LOG_CRITICAL);
 		isc_log_write(named_g_lctx, NAMED_LOGCATEGORY_GENERAL,
 			      NAMED_LOGMODULE_MAIN, ISC_LOG_CRITICAL,
 			      "exiting (due to assertion failure)");

lib/isc/assertions.c

@@ -95,8 +95,8 @@ isc_assertion_typetotext(isc_assertiontype_t type) {
 static void
 default_callback(const char *file, int line, isc_assertiontype_t type,
 		 const char *cond) {
-	void *tracebuf[BACKTRACE_MAXFRAME];
-	int nframes = isc_backtrace(tracebuf, BACKTRACE_MAXFRAME);
+	void *tracebuf[ISC_BACKTRACE_MAXFRAME];
+	int nframes = isc_backtrace(tracebuf, ISC_BACKTRACE_MAXFRAME);
 
 	fprintf(stderr, "%s:%d: %s(%s) failed%s\n", file, line,
 		isc_assertion_typetotext(type), cond,

lib/isc/backtrace.c

@@ -20,6 +20,7 @@
 #endif /* HAVE_BACKTRACE_SYMBOLS */
 
 #include <isc/backtrace.h>
+#include <isc/log.h>
 #include <isc/result.h>
 #include <isc/util.h>
 
@@ -60,6 +61,26 @@ isc_backtrace_symbols_fd(void *const *buffer, int size, int fd) {
 	backtrace_symbols_fd(buffer, size, fd);
 }
 
+void
+isc_backtrace_log(isc_log_t *lctx, isc_logcategory_t *category,
+		  isc_logmodule_t *module, int level) {
+	void *tracebuf[ISC_BACKTRACE_MAXFRAME];
+	int nframes;
+	char **strs;
+
+	nframes = isc_backtrace(tracebuf, ISC_BACKTRACE_MAXFRAME);
+	if (nframes <= 0) {
+		return;
+	}
+	strs = isc_backtrace_symbols(tracebuf, nframes);
+	if (strs == NULL) {
+		return;
+	}
+	for (int i = 0; i < nframes; i++) {
+		isc_log_write(lctx, category, module, level, "%s", strs[i]);
+	}
+}
+
 #else /* HAVE_BACKTRACE_SYMBOLS */
 
 int
@@ -85,4 +106,13 @@ isc_backtrace_symbols_fd(void *const *buffer, int size, int fd) {
 	UNUSED(fd);
 }
 
+void
+isc_backtrace_log(isc_log_t *lctx, isc_logcategory_t *category,
+		  isc_logmodule_t *module, int level) {
+	UNUSED(lctx);
+	UNUSED(category);
+	UNUSED(module);
+	UNUSED(level);
+}
+
 #endif /* HAVE_BACKTRACE_SYMBOLS */

lib/isc/include/isc/backtrace.h

@@ -34,6 +34,13 @@
  ***/
 #include <isc/types.h>
 
+/*
+ * The maximum number of stack frames to dump on assertion failure.
+ */
+#ifndef ISC_BACKTRACE_MAXFRAME
+#define ISC_BACKTRACE_MAXFRAME 128
+#endif /* ifndef ISC_BACKTRACE_MAXFRAME */
+
 /***
  *** Functions
  ***/
@@ -98,4 +105,11 @@ isc_backtrace_symbols_fd(void *const *buffer, int size, int fd);
  *\li	See platform NOTES for backtrace_symbols_fd for caveats
  */
 
+void
+isc_backtrace_log(isc_log_t *lctx, isc_logcategory_t *category,
+		  isc_logmodule_t *module, int level);
+/*
+ * Write a backtrace to the log.
+ */
+
 ISC_LANG_ENDDECLS