From 6a951aa9f705cf587370000c3b1c8e3e041112ba Mon Sep 17 00:00:00 2001
From: Nicolas Viennot <nicolas@viennot.biz>
Date: Wed, 6 Nov 2019 16:43:24 -0500
Subject: [PATCH] Improve debugging traces

---
 configure.ac  |  2 ++
 tmate-debug.c | 46 ++++++++++++++++++++++++++++++++++++++--------
 tmate-main.c  |  1 +
 tmate.h       |  1 +
 4 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/configure.ac b/configure.ac
index 856c588b..5262d670 100644
--- a/configure.ac
+++ b/configure.ac
@@ -100,6 +100,7 @@ AC_CHECK_HEADERS(
 		inttypes.h \
 		libutil.h \
 		ncurses.h \
+		execinfo.h \
 		ndir.h \
 		paths.h \
 		pty.h \
@@ -121,6 +122,7 @@ AC_CHECK_FUNCS(
 	[ \
 		dirfd \
 		flock \
+		backtrace \
 		setproctitle \
 		sysconf \
 		cfmakeraw \
diff --git a/tmate-debug.c b/tmate-debug.c
index 6bf74b0a..2a2b660d 100644
--- a/tmate-debug.c
+++ b/tmate-debug.c
@@ -1,9 +1,20 @@
+#ifdef HAVE_EXECINFO_H
 #include <execinfo.h>
+#endif
 #include <stdio.h>
 #include <stdlib.h>
 #include <regex.h>
+#include <signal.h>
 #include "tmate.h"
 
+#ifndef HAVE_BACKTRACE
+
+void tmate_print_stack_trace(void) {}
+void tmate_catch_sigsegv(void) {}
+void tmate_preload_trace_lib(void) {}
+
+#else
+
 #if DEBUG
 
 static int print_resolved_stack_frame(const char *frame)
@@ -47,7 +58,7 @@ static int print_resolved_stack_frame(const char *frame)
 		return -1;
 
 	line[strlen(line)-1] = 0; /* remove \n */
-	tmate_crit("%s(%s) [%s]", file, line, address);
+	tmate_debug("%s(%s) [%s]", file, line, address);
 	return 0;
 }
 #endif
@@ -59,23 +70,42 @@ void tmate_print_stack_trace(void)
 	char **strings;
 	size_t i;
 
-	size = backtrace(array, 20);
-	strings = backtrace_symbols(array, size);
+	size = backtrace (array, 20);
+	strings = backtrace_symbols (array, size);
 
-	tmate_crit("============ %zd stack frames ============", size);
+	tmate_info ("============ %zd stack frames ============", size);
 
 	for (i = 1; i < size; i++) {
 #if DEBUG
 		if (print_resolved_stack_frame(strings[i]) < 0)
 #endif
-			tmate_crit("%s", strings[i]);
+			tmate_info("%s", strings[i]);
 	}
 
-	free(strings);
+	free (strings);
+}
+
+static void handle_crash(__unused int sig)
+{
+	/*
+	 * XXX we are in a signal handler, we are not allowed to use malloc
+	 * and friends, which is what we do
+	 */
+	tmate_info("CRASH, printing stack trace");
+	tmate_print_stack_trace();
+	tmate_fatal("CRASHED");
+}
+
+void tmate_catch_sigsegv(void)
+{
+	signal(SIGSEGV, handle_crash);
+	signal(SIGABRT, handle_crash);
 }
 
 void tmate_preload_trace_lib(void)
 {
-	void *array[1];
-	backtrace(array, 1);
+       void *array[1];
+       backtrace(array, 1);
 }
+
+#endif
diff --git a/tmate-main.c b/tmate-main.c
index 55ab7319..eca4a6db 100644
--- a/tmate-main.c
+++ b/tmate-main.c
@@ -213,6 +213,7 @@ int main(int argc, char **argv, char **envp)
 	cmdline_end = *envp;
 
 	tmate_preload_trace_lib();
+	tmate_catch_sigsegv();
 
 	if ((dev_urandom_fd = open("/dev/urandom", O_RDONLY)) < 0)
 		tmate_fatal("Cannot open /dev/urandom");
diff --git a/tmate.h b/tmate.h
index 5fbd65da..fbcc9ebe 100644
--- a/tmate.h
+++ b/tmate.h
@@ -282,6 +282,7 @@ static inline bool tmate_has_websocket(void)
 
 extern void tmate_preload_trace_lib(void);
 extern void tmate_print_stack_trace(void);
+extern void tmate_catch_sigsegv(void);
 
 /* tmux.c */