vfs: code review fixes

- fix typo in readme
- remove unneeded extern declaration
- fix header guard macro
- tabs->spaces in syscalls.c (+1 squashed commit)
- fix minor typos

components/newlib/reent_init.c

@@ -0,0 +1,45 @@
+// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
+//
+// 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 <string.h>
+#include <sys/reent.h>
+#include "esp_attr.h"
+
+/* This function is not part on newlib API, it is defined in libc/stdio/local.h
+ * There is no nice way to get __cleanup member populated while avoiding __sinit,
+ * so extern declaration is used here.
+ */
+extern void _cleanup_r(struct _reent* r);
+
+/**
+ * This is the replacement for newlib's _REENT_INIT_PTR and __sinit.
+ * The problem with __sinit is that it allocates three FILE structures
+ * (stdin, stdout, stderr). Having individual standard streams for each task
+ * is a bit too much on a small embedded system. So we point streams
+ * to the streams of the global struct _reent, which are initialized in
+ * startup code.
+ */
+void IRAM_ATTR esp_reent_init(struct _reent* r)
+{
+    memset(r, 0, sizeof(*r));
+    r->_stdout = _GLOBAL_REENT->_stdout;
+    r->_stderr = _GLOBAL_REENT->_stderr;
+    r->_stdin  = _GLOBAL_REENT->_stdin;
+    r->__cleanup = &_cleanup_r;
+    r->__sdidinit = 1;
+    r->__sglue._next = NULL;
+    r->__sglue._niobs = 0;
+    r->__sglue._iobs = NULL;
+    r->_current_locale = "C";
+}