Isolated emscripten in new lib

lib/emscripten/emtests/test_stack_align.cpp

@@ -0,0 +1,34 @@
+// 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>
+
+#define ALIGN(num_bytes) __attribute__((aligned(num_bytes)))
+
+struct Aligned {
+  char ALIGN(4) a4;
+  char ALIGN(8) a8;
+  char ALIGN(16) a16;
+  char ALIGN(32) a32;
+};
+
+__attribute__((noinline))
+void Test(const void* p, int size) {
+  printf("align %d: %d\n", size, reinterpret_cast<size_t>(p) % size);
+}
+
+int main() {
+  Aligned a;
+  Test(&a.a4, 4);
+  Test(&a.a8, 8);
+  Test(&a.a16, 16);
+  Test(&a.a32, 32);
+
+  int p = reinterpret_cast<size_t>(&a);
+  printf("base align: %d, %d, %d, %d\n", p%4, p%8, p%16, p%32);
+
+  return 0;
+}
+