Isolated emscripten in new lib

lib/emscripten/emtests/stack_overflow.cpp

@@ -0,0 +1,39 @@
+// Copyright 2014 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>
+#include <stdlib.h>
+#include <stdint.h>
+#include <emscripten.h>
+
+void recurse(unsigned int x);
+
+void act(volatile unsigned int *a) {
+  printf("act     %d\n", *a);
+  unsigned int b = (int)(intptr_t)(alloca(*a));
+  if (b < *a) *a--;
+  recurse(*a);
+}
+
+void recurse(volatile unsigned int x) {
+  printf("recurse %d\n", x);
+  volatile unsigned int a = x;
+  volatile char buffer[1000*1000];
+  buffer[x/2] = 0;
+  buffer[(x-1)/2] = 0;
+  EM_ASM({});
+  if (x*x < x) {
+    act(&a);
+    if (a < x) x = a;
+    x--;
+  }
+  x += buffer[x/2];
+  if (x > 0) recurse(x-1);
+}
+
+int main() {
+  recurse(1000*1000);
+}
+