src: print backtrace on abort/unreachable code

Print a C backtrace on fatal errors to make it easier to debug issues.

PR-URL: https://github.com/nodejs/node/pull/6734
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

src/node.cc

@@ -2398,7 +2398,6 @@ static void OnFatalError(const char* location, const char* message) {
   } else {
     PrintErrorString("FATAL ERROR: %s\n", message);
   }
-  DumpBacktrace(stderr);
   fflush(stderr);
   ABORT();
 }

src/util.h

@@ -38,11 +38,18 @@ template <typename T> using remove_reference = std::remove_reference<T>;
 
 // Windows 8+ does not like abort() in Release mode
 #ifdef _WIN32
-#define ABORT() raise(SIGABRT)
+#define ABORT_NO_BACKTRACE() raise(SIGABRT)
 #else
-#define ABORT() abort()
+#define ABORT_NO_BACKTRACE() abort()
 #endif
 
+#define ABORT()                                                               \
+  do {                                                                        \
+    node::DumpBacktrace(stderr);                                              \
+    fflush(stderr);                                                           \
+    ABORT_NO_BACKTRACE();                                                     \
+  } while (0)
+
 #if defined(NDEBUG)
 # define ASSERT(expression)
 # define CHECK(expression)                                                    \