c 中对“getline"的未定义引用 [英] undefined reference to `getline' in c

问题描述

我正在学习在 C 编程中使用 getline，并尝试了来自 http://crasseux 的代码.com/books/ctutorial/getline.html

I am learning to use getline in C programming and tried the codes from http://crasseux.com/books/ctutorial/getline.html

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int atgc, char *argv[])
{
    int bytes_read = 1;
    int nbytes = 10;
    char *my_string;

    my_string = (char *)malloc(nbytes+1);

    puts("Please enter a line of text");

    bytes_read = getline(&my_string, &nbytes, stdin);

    if (bytes_read == -1)
    {
        puts ("ERROR!");
    }
    else
    {
        puts ("You typed:");
        puts (my_string);
    }

    return 0;
 }

然而，问题是编译器不断返回以下错误:未定义对'getline'的引用.你能告诉我是什么问题吗?谢谢！

However, the problem is that the compiler keeps returning errors of this: undefined reference to 'getline'. Could you please tell me what the problem is? Thank you!

我使用的是 Win7 64 位 + Eclipse Indigo + MinGW

I am using Win7 64bit + Eclipse Indigo + MinGW

推荐答案

其他答案已经涵盖了大部分内容，但存在几个问题.首先，getline() 不在 C 标准库中，但它是 POSIX 2008 的扩展.通常，它可用于兼容 POSIX 的编译器，因为宏 _POSIX_C_SOURCE 将使用适当的值定义.在 getline() 标准化之前，您可能有一个较旧的编译器，在这种情况下，这是一个 GNU 扩展，并且您必须在 #include < 之前 #define _GNU_SOURCE;stdio.h> 以启用它，并且必须使用与 GNU 兼容的编译器，例如 gcc.

The other answers have covered most of this, but there are several problems. First, getline() is not in the C standard library, but is a POSIX 2008 extension. Normally, it will be available with a POSIX-compatible compiler, as the macros _POSIX_C_SOURCE will be defined with the appropriate values. You possibly have an older compiler from before getline() was standardized, in which case this is a GNU extension, and you must #define _GNU_SOURCE before #include <stdio.h> to enable it, and must be using a GNU-compatible compiler, such as gcc.

此外，nbytes 的类型应该为 size_t，而不是 int.至少在我的系统上，这些大小不同，size_t 更长，使用 int* 而不是 size_t* 可以有严重的后果(并且也不能使用默认的 gcc 设置进行编译).有关详细信息，请参阅 getline 手册页 (http://linux.die.net/man/3/getline).

Additionally, nbytes should have type size_t, not int. On my system, at least, these are of different size, with size_t being longer, and using an int* instead of a size_t* can have grave consequences (and also doesn't compile with default gcc settings). See the getline manual page (http://linux.die.net/man/3/getline) for details.

进行更改后，您的程序可以编译并在我的系统上正常运行.

With that change made, your program compiles and runs fine on my system.

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