Isolated emscripten in new lib

lib/emscripten/emtests/test_vsnprintf.c

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2016 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 <stdarg.h>
+#include <stdint.h>
+
+void printy(const char *f, ...) {
+  char buffer[256];
+  va_list args;
+  va_start(args, f);
+  vsnprintf(buffer, 256, f, args);
+  puts(buffer);
+  va_end(args);
+}
+
+int main(int argc, char **argv) {
+  int64_t x = argc - 1;
+  int64_t y = argc - 1 + 0x400000;
+  if (x % 3 == 2) y *= 2;
+
+  printy("0x%llx_0x%llx", x, y);
+  printy("0x%llx_0x%llx", x, x);
+  printy("0x%llx_0x%llx", y, x);
+  printy("0x%llx_0x%llx", y, y);
+
+  {
+    uint64_t A = 0x800000;
+    uint64_t B = 0x800000000000ULL;
+    printy("0x%llx_0x%llx", A, B);
+  }
+  {
+    uint64_t A = 0x800;
+    uint64_t B = 0x12340000000000ULL;
+    printy("0x%llx_0x%llx", A, B);
+  }
+  {
+    uint64_t A = 0x000009182746756;
+    uint64_t B = 0x192837465631ACBDULL;
+    printy("0x%llx_0x%llx", A, B);
+  }
+
+  return 0;
+}