Add support for printing backtraces on segfault

Enabled in debug mode (make all-debug).

configure.ac

@@ -11,7 +11,7 @@ m4_pattern_forbid([^AX_])
 
 AC_PROG_CC
 
-AC_CHECK_HEADERS([stdint.h stdlib.h string.h sys/time.h unistd.h wordexp.h])
+AC_CHECK_HEADERS([execinfo.h stdint.h stdlib.h string.h sys/time.h unistd.h wordexp.h])
 AC_CHECK_FUNCS([gettimeofday])
 AC_CHECK_DECLS([environ])
 AC_CHECK_DECLS([errno], [], [], [#include <errno.h>])

contrib/config.make-Darwin

@@ -3,6 +3,7 @@
 # Work-around for Homebrew-based xmlto.
 export XML_CATALOG_FILES=/usr/local/etc/xml/catalog
 
+TIG_CFLAGS += -DHAVE_EXECINFO_H
 TIG_LDLIBS = -liconv
 
 NCURSES_DIR = $(wildcard /usr/local/opt/ncurses)

include/tig/tig.h

@@ -60,6 +60,10 @@
 #include <langinfo.h>
 #include <iconv.h>
 
+#ifdef HAVE_EXECINFO_H
+#include <execinfo.h>
+#endif
+
 /* ncurses(3): Must be defined to have extended wide-character functions. */
 #define _XOPEN_SOURCE_EXTENDED 1
 

include/tig/util.h

@@ -116,5 +116,7 @@ name(type **mem, size_t size, size_t increase)					\
 	return tmp;								\
 }
 
+void sigsegv_handler(int sig);
+
 #endif
 /* vim: set ts=8 sw=8 noexpandtab: */

src/tig.c

@@ -627,6 +627,43 @@ handle_mouse_event(void)
 }
 #endif
 
+/*
+ * Error handling.
+ *
+ * Inspired by code from src/util.c in ELinks
+ * (f86be659718c0cd0a67f88b42f07044c23d0d028).
+ */
+
+#ifdef DEBUG
+void
+sigsegv_handler(int sig)
+{
+	if (die_callback)
+		die_callback();
+
+	fputs("Tig crashed!\n\n"
+	      "Please report this issue along with all info printed below to\n\n"
+	      "  https://github.com/jonas/tig/issues/new\n\n", stderr);
+
+	fputs("Tig version: ", stderr);
+	fputs(TIG_VERSION, stderr);
+	fputs("\n\n", stderr);
+
+#ifdef HAVE_EXECINFO_H
+	{
+		/* glibc way of doing this */
+		void *stack[20];
+		size_t size = backtrace(stack, 20);
+
+		backtrace_symbols_fd(stack, size, STDERR_FILENO);
+	}
+#endif
+
+	/* The fastest way OUT! */
+	abort();
+}
+#endif
+
 struct key_combo {
 	enum request request;
 	struct keymap *keymap;
@@ -690,6 +727,11 @@ main(int argc, const char *argv[])
 	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
 		die("Failed to setup signal handler");
 
+#ifdef DEBUG
+	if (signal(SIGSEGV, sigsegv_handler) == SIG_ERR)
+		die("Failed to setup signal handler");
+#endif
+
 	if (setlocale(LC_ALL, "")) {
 		codeset = nl_langinfo(CODESET);
 	}