[标准化libc] fix CI warning

components/dfs/src/dfs_posix.c

@@ -110,11 +110,7 @@ RTM_EXPORT(close);
  * @return the actual read data buffer length. If the returned value is 0, it
  * may be reach the end of file, please check errno.
  */
-#if defined(RT_USING_NEWLIB) && defined(_EXFUN)
-_READ_WRITE_RETURN_TYPE _EXFUN(read, (int fd, void *buf, size_t len))
-#else
-int read(int fd, void *buf, size_t len)
-#endif
+ssize_t read(int fd, void *buf, size_t len)
 {
     int result;
     struct dfs_fd *d;
@@ -154,11 +150,7 @@ RTM_EXPORT(read);
  *
  * @return the actual written data buffer length.
  */
-#if defined(RT_USING_NEWLIB) && defined(_EXFUN)
-_READ_WRITE_RETURN_TYPE _EXFUN(write, (int fd, const void *buf, size_t len))
-#else
-int write(int fd, const void *buf, size_t len)
-#endif
+ssize_t write(int fd, const void *buf, size_t len)
 {
     int result;
     struct dfs_fd *d;

components/libc/compilers/common/none-gcc/sys/unistd.h

@@ -18,8 +18,8 @@
 #define STDOUT_FILENO   1       /* standard output file descriptor */
 #define STDERR_FILENO   2       /* standard error file descriptor */
 
-int read(int fd, void *buf, size_t len);
-int write(int fd, const void *buf, size_t len);
+ssize_t read(int fd, void *buf, size_t len);
+ssize_t write(int fd, const void *buf, size_t len);
 off_t lseek(int fd, off_t offset, int whence);
 int fsync(int fildes);
 int unlink(const char *pathname);