关于fdopendir 的 奇怪 warning

坏坏小少

#include <sys/types.h> #include <dirent.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <stdlib.h> int main() { &nbsp;&nbsp;&nbsp;&nbsp;int fd; &nbsp;&nbsp;&nbsp;&nbsp;DIR *dir; &nbsp;&nbsp;&nbsp;&nbsp;struct dirent *dir_str; &nbsp;&nbsp;&nbsp;&nbsp;fd = open("/",O_RDONLY); &nbsp;&nbsp;&nbsp;&nbsp;dir = opendir("/"); &nbsp;&nbsp;&nbsp;&nbsp;dir = fdopendir(fd);  //用opendir 则没有warning &nbsp;&nbsp;&nbsp;&nbsp;while ((dir_str = readdir(dir)) != NULL){ &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;printf("%s\n",dir_str->d_name); &nbsp;&nbsp;&nbsp;&nbsp;} &nbsp;&nbsp;&nbsp;&nbsp;closedir(dir); &nbsp;&nbsp;&nbsp;&nbsp;close(fd); &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;return 0; }

gcc fdopendir.c
得到
fdopendir.c: In function 'main':
fdopendir.c:17: warning: assignment makes pointer from integer without a cast

可是man opendir

RETURN VALUE
       The opendir() and fdopendir() functions return a  pointer  to  the  directory
       stream.  On error, NULL is returned, and errno is set appropriately.
绝不是integer
十分不解

zhuhefang2006

我的系统man opendir
并没有你提到的fdopendir()这个函数啊
RETURN VALUE
       The opendir() and fdopendir() functions return a  pointer  to  the  directory
       stream.  On error, NULL is returned, and errno is set appropriately.


如果是因为fdopendir()这个函数不存在
则出现warning提示是因为: 没有定义的函数有个默认的返回值int

坏坏小少

原帖由 zhuhefang2006 于 2008-5-1 15:33 发表
我的系统man opendir
并没有你提到的fdopendir()这个函数啊
RETURN VALUE
       The opendir() and fdopendir() functions return a  pointer  to  the  directory
       stream.  On error, NULL is ret ...

VERSIONS
       fdopendir() is available in glibc since version 2.4.

CONFORMING TO
       opendir() is present on SVr4, 4.3BSD, and specified in POSIX.1-2001.
       fdopendir() is under consideration for inclusion in the next version
       of POSIX.1.
FreeBSD 尚未实现呢
不知道楼上用的哪种类 UNIX
我的gcc
$gcc -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-4.1.2/work/gcc-4.1.2/configure --prefix=/usr --bindir=/usr/i686-pc-linux-gnu/gcc-bin/4.1.2 --includedir=/usr/lib/gcc/i686-pc-linux-gnu/4.1.2/include --datadir=/usr/share/gcc-data/i686-pc-linux-gnu/4.1.2 --mandir=/usr/share/gcc-data/i686-pc-linux-gnu/4.1.2/man --infodir=/usr/share/gcc-data/i686-pc-linux-gnu/4.1.2/info --with-gxx-include-dir=/usr/lib/gcc/i686-pc-linux-gnu/4.1.2/include/g++-v4 --host=i686-pc-linux-gnu --build=i686-pc-linux-gnu --disable-altivec --enable-nls --without-included-gettext --with-system-zlib --disable-checking --disable-werror --enable-secureplt --disable-multilib --enable-libmudflap --disable-libssp --disable-libgcj --with-arch=i686 --enable-languages=c,c++,treelang,fortran --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
Thread model: posix
gcc version 4.1.2 (Gentoo 4.1.2 p1.1)