>From aff37074abd0431e5bbcad370ceea3c9a2ed56c4 Mon Sep 17 00:00:00 2001
From: Brand Huntsman <address@hidden>
Date: Fri, 19 Jan 2018 04:42:50 -0700
Subject: [PATCH] restore terminal and print backtrace for segfaults and
 assertions

Signed-off-by: Brand Huntsman <address@hidden>
---
 src/Makefile.am |  3 +++
 src/nano.c      | 39 ++++++++++++++++++++++++++++++++++++---
 src/nano.h      | 10 +++++++++-
 src/proto.h     |  2 ++
 4 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/src/Makefile.am b/src/Makefile.am
index 625434c2..f9422e47 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,6 +1,9 @@
 AM_CPPFLAGS = -DLOCALEDIR=\"$(localedir)\" -DSYSCONFDIR=\"$(sysconfdir)\" \
 	-I$(top_builddir)/lib -I$(top_srcdir)/lib
 
+# -rdynamic is needed by print_backtrace() to show function names
+LDFLAGS = -rdynamic
+
 CLEANFILES = revision.h
 
 if BUILDING_FROM_GIT
diff --git a/src/nano.c b/src/nano.c
index a21625cf..dd2519ec 100644
--- a/src/nano.c
+++ b/src/nano.c
@@ -549,6 +549,13 @@ void say_there_is_no_help(void)
 }
 #endif
 
+/* Make nano exit semi-gracefully during a crash. */
+void crash_finish(void)
+{
+	endwin();
+	tcsetattr(0, TCSANOW, &oldterm);
+}
+
 /* Make nano exit gracefully. */
 void finish(void)
 {
@@ -1890,8 +1897,37 @@ void do_output(char *output, size_t output_len, bool allow_cntrls)
 		update_line(openfile->current, openfile->current_x);
 }
 
+void print_backtrace(int skip_to)
+{
+	void *callstack[16];
+	int i, frames = backtrace(callstack, 16);
+	char **strings = backtrace_symbols(callstack, frames);
+	for (i = skip_to + 1; i < frames; i++){
+		/* +1 skips print_backtrace() */
+		IGNORE_CALL_RESULT(write(2, "|  ", 3));
+		IGNORE_CALL_RESULT(write(2, strings[i], strlen(strings[i])));
+		IGNORE_CALL_RESULT(write(2, "\n", 1));
+	}
+	free(strings);
+	exit(1);
+}
+
+static const char segfault_msg[] = "Segmentation fault\n";
+static void segfault_handler(int nothing)
+{
+	crash_finish();
+	IGNORE_CALL_RESULT(write(2, segfault_msg, sizeof(segfault_msg)));
+	print_backtrace(1); /* +1 skips segfault_handler() */
+}
+
 int main(int argc, char **argv)
 {
+	/* Initialize segfault handler. */
+	signal(SIGSEGV, segfault_handler);
+
+	/* Back up the terminal settings so that they can be restored. */
+	tcgetattr(0, &oldterm);
+
 	int stdin_flags, optchr;
 #if defined(ENABLED_WRAPORJUSTIFY) && defined(ENABLE_NANORC)
 	bool fill_used = FALSE;
@@ -1985,9 +2021,6 @@ int main(int argc, char **argv)
 	console = (getenv("DISPLAY") == NULL);
 #endif
 
-	/* Back up the terminal settings so that they can be restored. */
-	tcgetattr(0, &oldterm);
-
 	/* Get the state of standard input and ensure it uses blocking mode. */
 	stdin_flags = fcntl(0, F_GETFL, 0);
 	if (stdin_flags != -1)
diff --git a/src/nano.h b/src/nano.h
index 55abf1e8..edbb9c5b 100644
--- a/src/nano.h
+++ b/src/nano.h
@@ -120,7 +120,15 @@
 #include <dirent.h>
 #include <regex.h>
 #include <signal.h>
-#include <assert.h>
+#include <unistd.h>
+#include <execinfo.h>
+
+#define assert(expr) if(!(expr)){ \
+	crash_finish(); \
+	fprintf(stderr, "Assertion (%s) failed: %s %s() %d\n", \
+			#expr, __FILE__, __func__, __LINE__); \
+	print_backtrace(0); \
+}
 
 /* If we aren't using an ncurses with mouse support, exclude any
  * mouse routines, as they are useless then. */
diff --git a/src/proto.h b/src/proto.h
index 77ffc05c..6b086a84 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -420,6 +420,7 @@ void show_restricted_warning(void);
 #ifndef ENABLE_HELP
 void say_there_is_no_help(void);
 #endif
+void crash_finish(void);
 void finish(void);
 void die(const char *msg, ...);
 void die_save_file(const char *die_filename, struct stat *die_stat);
@@ -446,6 +447,7 @@ int do_input(bool allow_funcs);
 int do_mouse(void);
 #endif
 void do_output(char *output, size_t output_len, bool allow_cntrls);
+void print_backtrace(int skip_to);
 
 /* Most functions in prompt.c. */
 #ifdef ENABLE_MOUSE
-- 
2.13.6