libc: Implement tmpfile() function

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
Change-Id: I00bdb42006b40bf1b9bc0bb6865b9b88b4acbb7b

include/stdio.h

@@ -210,6 +210,7 @@ int    vdprintf(int fd, FAR const IPTR char *fmt, va_list ap);
 
 /* Operations on paths */
 
+FAR FILE *tmpfile(void);
 FAR char *tmpnam(FAR char *s);
 FAR char *tempnam(FAR const char *dir, FAR const char *pfx);
 int       remove(FAR const char *path);

libs/libc/stdio/Make.defs

@@ -60,7 +60,7 @@ CSRCS += lib_stdinstream.c lib_stdoutstream.c lib_stdsistream.c
 CSRCS += lib_stdsostream.c lib_perror.c lib_feof.c lib_ferror.c
 CSRCS += lib_rawinstream.c lib_rawoutstream.c lib_rawsistream.c
 CSRCS += lib_rawsostream.c lib_remove.c lib_clearerr.c lib_scanf.c
-CSRCS += lib_fscanf.c lib_vfscanf.c
+CSRCS += lib_fscanf.c lib_vfscanf.c lib_tmpfile.c
 
 endif
 

libs/libc/stdio/lib_tmpfile.c

@@ -0,0 +1,51 @@
+/****************************************************************************
+ * libs/libc/stdio/lib_tmpfile.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you 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.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+FAR FILE *tmpfile(void)
+{
+  char path[L_tmpnam] = "/tmp/XXXXXX.tmp";
+  FAR FILE *fp = NULL;
+  int fd;
+
+  fd = mkstemp(path);
+  if (fd >= 0)
+    {
+      unlink(fd);
+      fp = fdopen(fd, "w+");
+      if (fp == NULL)
+        {
+          close(fd);
+        }
+    }
+
+  return fp;
+}