是的crypt（）函数unistd.h中或crypt.h声明？

问题描述

我使用GCC 4.6.0（上的其它身份不明的平台的）。

I'm using GCC 4.6.0 (on an otherwise unidentified platform).

我使用的是的crypt（）函数加密的密码。

I am using the crypt() function to encrypt a password.

我从来没有使用该功能之前，所以我检查了主要的页面：

I have never used that function before so I checked out the main page:

man 3 crypt

和它说包含 unistd.h中头。

然而，当我这样做，我得到了地穴函数进行隐含的警告。

However, when I did that, I got an implicit warning for the crypt function.

warning: implicit declaration of function ‘crypt’ [-Wimplicit-function-declaration]

我做了一些搜索和我发现，你必须包括 crypt.h 。但是，怎么来的不说，在手册页？

I did a bit of searching and I found that you have to include the crypt.h. However, how come it doesn't say that in the man page?

推荐答案

它还说的#define _XOPEN_SOURCE （包括前unistd.h中）。所以，你应该把它添加到暴露隐窝声明。

It also says #define _XOPEN_SOURCE (before including unistd.h) in my man page. So you should probably add it to expose the declaration of crypt.

修改

我刚刚试了一下。包括 unistd.h中的和的的#define _XOPEN_SOURCE 它的伎俩了。包括单打独斗是不够的。

I just tried it. Including unistd.h and #define _XOPEN_SOURCE before it does the trick. Including it alone isn't enough.

使用

gcc version 4.6.0 20110429
GNU C Library stable release version 2.13

展望 unistd.h中：

/* XPG4.2 specifies that prototypes for the encryption functions must
   be defined here.  */
#ifdef  __USE_XOPEN
/* Encrypt at most 8 characters from KEY using salt to perturb DES.  */
extern char *crypt (__const char *__key, __const char *__salt)
     __THROW __nonnull ((1, 2));

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