Fix tmpfile(3).

This could be better, but at least now it works.

Change-Id: I88b7cf3f7ce8e5fa0b3fe678b7d1679a68ffffc9

tests/stdio_test.cpp

@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gtest/gtest.h>
+
+#include <errno.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+TEST(stdio, tmpfile_fileno_fprintf_rewind_fgets) {
+  FILE* fp = tmpfile();
+  ASSERT_TRUE(fp != NULL);
+
+  int fd = fileno(fp);
+  ASSERT_NE(fd, -1);
+
+  struct stat sb;
+  int rc = fstat(fd, &sb);
+  ASSERT_NE(rc, -1);
+  ASSERT_EQ(sb.st_mode & 0777, 0600U);
+
+  rc = fprintf(fp, "hello\n");
+  ASSERT_EQ(rc, 6);
+
+  rewind(fp);
+
+  char buf[16];
+  char* s = fgets(buf, sizeof(buf), fp);
+  ASSERT_TRUE(s != NULL);
+  ASSERT_STREQ("hello\n", s);
+
+  fclose(fp);
+}