From 2f1227eb3f1c7f08d9c0dbecc426c3960e98c867 Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Fri, 22 Jan 2021 12:12:29 +0100
Subject: [PATCH] MINOR: debug: always export the my_backtrace function

In order to simplify the code and remove annoying ifdefs everywhere,
let's always export my_backtrace() and make it adapt to the situation
and return zero if not supported. A small update in the thread dump
function was needed to make sure we don't use its results if it fails
now.
---
 include/haproxy/tools.h | 6 +++---
 src/debug.c             | 8 ++------
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/include/haproxy/tools.h b/include/haproxy/tools.h
index 76e6e730c0..5be00b7fcb 100644
--- a/include/haproxy/tools.h
+++ b/include/haproxy/tools.h
@@ -993,13 +993,14 @@ int may_access(const void *ptr);
 const void *resolve_sym_name(struct buffer *buf, const char *pfx, const void *addr);
 const char *get_exec_path();
 
-#if defined(USE_BACKTRACE)
 /* Note that this may result in opening libgcc() on first call, so it may need
  * to have been called once before chrooting.
  */
 static forceinline int my_backtrace(void **buffer, int max)
 {
-#ifdef HA_HAVE_WORKING_BACKTRACE
+#if !defined(USE_BACKTRACE)
+	return 0;
+#elif defined(HA_HAVE_WORKING_BACKTRACE)
 	return backtrace(buffer, max);
 #else
 	const struct frame {
@@ -1016,7 +1017,6 @@ static forceinline int my_backtrace(void **buffer, int max)
 	return count;
 #endif
 }
-#endif
 
 /* same as realloc() except that ptr is also freed upon failure */
 static inline void *my_realloc2(void *ptr, size_t size)
diff --git a/src/debug.c b/src/debug.c
index 460ee4d3c5..3202814732 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -100,7 +100,6 @@ void ha_thread_dump(struct buffer *buf, int thr, int calling_tid)
 	chunk_appendf(buf, "             curr_task=");
 	ha_task_dump(buf, sched->current, "             ");
 
-#ifdef USE_BACKTRACE
 	if (stuck) {
 		/* We only emit the backtrace for stuck threads in order not to
 		 * waste precious output buffer space with non-interesting data.
@@ -119,7 +118,7 @@ void ha_thread_dump(struct buffer *buf, int thr, int calling_tid)
 		if (nptrs)
 			chunk_appendf(buf, "             call trace(%d):\n", nptrs);
 
-		for (j = 0; j < nptrs || dump < 2; j++) {
+		for (j = 0; nptrs && (j < nptrs || dump < 2); j++) {
 			if (j == nptrs && !dump) {
 				/* we failed to spot the starting point of the
 				 * dump, let's start over dumping everything we
@@ -162,7 +161,6 @@ void ha_thread_dump(struct buffer *buf, int thr, int calling_tid)
 			chunk_appendf(buf, "\n");
 		}
 	}
-#endif
 }
 
 
@@ -1094,15 +1092,13 @@ static int init_debug_per_thread()
 static int init_debug()
 {
 	struct sigaction sa;
+	void *callers[1];
 
-#ifdef USE_BACKTRACE
 	/* calling backtrace() will access libgcc at runtime. We don't want to
 	 * do it after the chroot, so let's perform a first call to have it
 	 * ready in memory for later use.
 	 */
-	void *callers[1];
 	my_backtrace(callers, sizeof(callers)/sizeof(*callers));
-#endif
 	sa.sa_handler = NULL;
 	sa.sa_sigaction = debug_handler;
 	sigemptyset(&sa.sa_mask);