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7e67d2d906
readdir() returned NULL at end-of-directory without ensuring errno was clean. POSIX requires errno to be unchanged at EOF, but the underlying read() path may leave a stale errno value. Callers that follow the POSIX idiom (set errno to 0 before the call, test it after a NULL return), such as readdir_r() and scandir(), then misread this as a readdir() failure. Save errno on entry and restore it on the end-of-directory return so that EOF no longer reports a spurious error, while genuine errors (read() returning a negative value) still propagate. Signed-off-by: yushuailong <yyyusl@qq.com>
89 lines
3 KiB
C
89 lines
3 KiB
C
/****************************************************************************
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* libs/libc/dirent/lib_readdir.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <dirent.h>
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#include <errno.h>
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#include <unistd.h>
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: readdir
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*
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* Description:
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* The readdir() function returns a pointer to a dirent structure
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* representing the next directory entry in the directory stream pointed
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* to by dir. It returns NULL on reaching the end-of-file or if an error
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* occurred.
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*
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* Input Parameters:
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* dirp -- An instance of type DIR created by a previous call to opendir();
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*
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* Returned Value:
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* The readdir() function returns a pointer to a dirent structure, or NULL
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* if an error occurs or end-of-file is reached. On error, errno is set
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* appropriately.
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*
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* EBADF - Invalid directory stream descriptor dir
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*
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****************************************************************************/
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FAR struct dirent *readdir(DIR *dirp)
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{
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int errcode;
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int ret;
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if (!dirp)
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{
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set_errno(EBADF);
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return NULL;
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}
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/* Save errno so it can be restored on end-of-directory. POSIX requires
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* errno to be unchanged at EOF, but the read() path may not preserve it.
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*/
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errcode = get_errno();
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ret = read(dirp->fd, &dirp->entry, sizeof(struct dirent));
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if (ret == 0)
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{
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set_errno(errcode); /* EOF: restore errno (not an error) */
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return NULL;
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}
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else if (ret < 0)
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{
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return NULL; /* error: read() already set errno */
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}
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return &dirp->entry;
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}
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