error C2065: 'nocreate' : undeclared identifier

最新推荐文章于 2021-05-24 16:53:50 发布

米车阿里

最新推荐文章于 2021-05-24 16:53:50 发布

阅读量6.7k

点赞数 1

CC 4.0 BY-SA版权

文章标签： c iostream constants library function ios

本文链接：https://blog.youkuaiyun.com/michealmeng555/article/details/6529665

VS2010琐碎专栏收录该内容

5 篇文章

订阅专栏

本文讨论了C++新旧iostream库之间的变化，特别是废弃了如ios::nocreate等特性，并提供了替代方案来检查文件是否存在。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

In addition to the above changes, the following functions, constants, and enumerators that are elements of the old iostream library are not elements of the new iostream library:

attach member function of filebuf, fstream ifstream, and ofstream
fd member function of filebuf, fstream ifstream, and ofstream
filebuf::openprot
filebuf::setmode
ios::bitalloc
ios::nocreate
ios::noreplace
ios::sync_with_stdio
streambuf::out_waiting
streambuf::setbuf (use rdbuf -> pubsetbuf for the same behavior)

what's the .net replacement for ios::nocreate

"John Harrison" <> wrote in message news:<>...

> > In the new VC++ 7.0 ios::nocreate is obsolete. Does any one know what
> > I should do to achieve the same goal? I really want to check if a
> > file exists before reading from it.
> >

>
> There is no need for nocreate. If you open a file for reading and the file
> doesn't exist, then the open will fail. Nocreate is the default if you like.

所以不用nocreate也是可以的

在C++中

#include <fstream>
#include <iostream>
using namespace std;

使用ios::nocreate会报告错误：

error C2039: 'nocreate' : is not a member of 'basic_ios<char,struct std::char_traits<char> >'
error C2065: 'nocreate' : undeclared identifier
执行 cl.exe 时出错.

在C中

#include<fstream.h>

#include<stdlib.h>

可以直接使用

原因在于

ios::nocreate是在C++标准制定之前在<fstream.h>中有定义的。但是因为它跟系统平台相关密切，所以在C++标准中去掉了对它的支持。