Isolated emscripten in new lib

lib/emscripten/emtests/test_ccall.cpp

@@ -0,0 +1,54 @@
+// 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>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <emscripten.h>
+
+extern "C" {
+int get_int() { return 5; }
+float get_float() { return 3.14; }
+bool get_bool() { return true; }
+const char *get_string() { return "hello world"; }
+void print_int(int x) { printf("%d\n", x); }
+void print_float(float x) { printf("%.2f\n", x); }
+void print_string(char *x) { printf("%s\n", x); }
+void print_bool(bool x) { 
+  if (x) printf("true\n"); 
+  else if (!x) printf("false\n");
+}
+int multi(int x, float y, int z, char *str) {
+  if (x) puts(str);
+  return (x + y) * z;
+}
+int *pointer(int *in) {
+  printf("%d\n", *in);
+  static int ret = 21;
+  return &ret;
+}
+
+// This test checks that ccall restores the stack correctly to whatever it was
+// when ccall was entered.  We save the stack pointer on the heap in stackChecker
+// and verify that ccall restores it correctly.
+struct test_struct {
+  int arg1, arg2, arg3;
+};
+static int* stackChecker = 0;
+__attribute__((noinline))
+int get_stack() { int i; return (int)&i; }
+int uses_stack(test_struct* t1) {
+  if (stackChecker == 0) stackChecker = (int*)malloc(sizeof(int));
+  *stackChecker = get_stack();
+  EM_ASM(Module['ccall']('get_int', 'number'));
+  printf("stack is %s.\n", *stackChecker == get_stack() ? "ok" : "messed up");
+  return 0;
+}
+void call_ccall_again() {
+  test_struct t1 = { 1, 2, 3 };
+  uses_stack(&t1);
+}
+}
+