Isolated emscripten in new lib

lib/emscripten/emtests/test_exceptions_multi.cpp

@@ -0,0 +1,55 @@
+// Copyright 2017 The Emscripten Authors.  All rights reserved.
+// Emscripten is available under two separate licenses, the MIT license and the
+// University of Illinois/NCSA Open Source License.  Both these licenses can be
+// found in the LICENSE file.
+
+#include <stdio.h>
+
+static int current_exception_id = 0;
+
+typedef struct {
+  int jmp;
+} jmp_state;
+
+void setjmp_func(jmp_state* s, int level) {
+  int prev_jmp = s->jmp;
+  int c_jmp;
+
+  if (level == 2) {
+    printf("level is 2, perform longjmp!\n");
+    throw 1;
+  }
+
+  c_jmp = current_exception_id++;
+  try {
+    printf("setjmp normal execution path, level: %d, prev_jmp: %d\n", level,
+           prev_jmp);
+    s->jmp = c_jmp;
+    setjmp_func(s, level + 1);
+  }
+  catch (int caught_eid) {
+    printf("caught %d\n", caught_eid);
+    if (caught_eid == c_jmp) {
+      printf("setjmp exception execution path, level: %d, prev_jmp: %d\n",
+             level, prev_jmp);
+      if (prev_jmp != -1) {
+        printf("prev_jmp is not empty, continue with longjmp!\n");
+        s->jmp = prev_jmp;
+        throw s->jmp;
+      }
+    } else {
+      throw;
+    }
+  }
+
+  printf("Exiting setjmp function, level: %d, prev_jmp: %d\n", level, prev_jmp);
+}
+
+int main(int argc, char* argv[]) {
+  jmp_state s;
+  s.jmp = -1;
+
+  setjmp_func(&s, 0);
+
+  return 0;
+}