是否可以重复导致编译错误的C源代码？

Question

按照另一个question I had asked earlier我想我可能已经找到了我的问题，但我需要专家的眼球。

我发现文件/net/ipv4/tcp_zero_copy.c这导致了我的内核编译失败。

当我在C/C++编辑器中查看文件时，我对C或C++没有多少了解，它看起来像相同的代码重复了一遍（我认为是4次）。

我的问题很简单;

这足以导致编译器出现问题吗？如果相同的代码在同一个文件中反复出现？

这是该文件的源代码（总共148行，从头到尾）;

/* 
* Support routines for TCP zero copy transmit 
* 
* Created by Vladislav Bolkhovitin 
* 
* This program is free software; you can redistribute it and/or 
*  modify it under the terms of the GNU General Public License 
*  version 2 as published by the Free Software Foundation. 
*/ 

#include <linux/skbuff.h> 

net_get_page_callback_t net_get_page_callback __read_mostly; 
EXPORT_SYMBOL(net_get_page_callback); 

net_put_page_callback_t net_put_page_callback __read_mostly; 
EXPORT_SYMBOL(net_put_page_callback); 

/* 
* Caller of this function must ensure that at the moment when it's called 
* there are no pages in the system with net_priv field set to non-zero 
* value. Hence, this function, as well as net_get_page() and net_put_page(), 
* don't need any protection. 
*/ 
int net_set_get_put_page_callbacks(
    net_get_page_callback_t get_callback, 
    net_put_page_callback_t put_callback) 
{ 
    int res = 0; 

    if ((net_get_page_callback != NULL) && (get_callback != NULL) && 
     (net_get_page_callback != get_callback)) { 
     res = -EBUSY; 
     goto out; 
    } 

    if ((net_put_page_callback != NULL) && (put_callback != NULL) && 
     (net_put_page_callback != put_callback)) { 
     res = -EBUSY; 
     goto out; 
    } 

    net_get_page_callback = get_callback; 
    net_put_page_callback = put_callback; 

out: 
    return res; 
} 
EXPORT_SYMBOL(net_set_get_put_page_callbacks); 
/* 
* Support routines for TCP zero copy transmit 
* 
* Created by Vladislav Bolkhovitin 
* 
* This program is free software; you can redistribute it and/or 
*  modify it under the terms of the GNU General Public License 
*  version 2 as published by the Free Software Foundation. 
*/ 

#include <linux/skbuff.h> 

net_get_page_callback_t net_get_page_callback __read_mostly; 
EXPORT_SYMBOL(net_get_page_callback); 

net_put_page_callback_t net_put_page_callback __read_mostly; 
EXPORT_SYMBOL(net_put_page_callback); 

/* 
* Caller of this function must ensure that at the moment when it's called 
* there are no pages in the system with net_priv field set to non-zero 
* value. Hence, this function, as well as net_get_page() and net_put_page(), 
* don't need any protection. 
*/ 
int net_set_get_put_page_callbacks(
    net_get_page_callback_t get_callback, 
    net_put_page_callback_t put_callback) 
{ 
    int res = 0; 

    if ((net_get_page_callback != NULL) && (get_callback != NULL) && 
     (net_get_page_callback != get_callback)) { 
     res = -EBUSY; 
     goto out; 
    } 

    if ((net_put_page_callback != NULL) && (put_callback != NULL) && 
     (net_put_page_callback != put_callback)) { 
     res = -EBUSY; 
     goto out; 
    } 

    net_get_page_callback = get_callback; 
    net_put_page_callback = put_callback; 

out: 
    return res; 
} 
EXPORT_SYMBOL(net_set_get_put_page_callbacks); 
/* 
* Support routines for TCP zero copy transmit 
* 
* Created by Vladislav Bolkhovitin 
* 
* This program is free software; you can redistribute it and/or 
*  modify it under the terms of the GNU General Public License 
*  version 2 as published by the Free Software Foundation. 
*/ 

#include <linux/skbuff.h> 

net_get_page_callback_t net_get_page_callback __read_mostly; 
EXPORT_SYMBOL(net_get_page_callback); 

net_put_page_callback_t net_put_page_callback __read_mostly; 
EXPORT_SYMBOL(net_put_page_callback); 

/* 
* Caller of this function must ensure that at the moment when it's called 
* there are no pages in the system with net_priv field set to non-zero 
* value. Hence, this function, as well as net_get_page() and net_put_page(), 
* don't need any protection. 
*/ 
int net_set_get_put_page_callbacks(
    net_get_page_callback_t get_callback, 
    net_put_page_callback_t put_callback) 
{ 
    int res = 0; 

    if ((net_get_page_callback != NULL) && (get_callback != NULL) && 
     (net_get_page_callback != get_callback)) { 
     res = -EBUSY; 
     goto out; 
    } 

    if ((net_put_page_callback != NULL) && (put_callback != NULL) && 
     (net_put_page_callback != put_callback)) { 
     res = -EBUSY; 
     goto out; 
    } 

    net_get_page_callback = get_callback; 
    net_put_page_callback = put_callback; 

out: 
    return res; 
} 
EXPORT_SYMBOL(net_set_get_put_page_callbacks); 

**编辑**

而且我只是用记事本++到它看起来像他们结束的代码的各个块进行比较。根据比较工具全部3块互相匹配。

这是从它死亡的地方到它返回给我的命令提示符的编译器输出。

CC  net/ipv4/tcp_zero_copy.o 
net/ipv4/tcp_zero_copy.c:63:1: error: redefinition of â__kcrctab_net_get_page_callbackâ 
net/ipv4/tcp_zero_copy.c:14:1: note: previous definition of â__kcrctab_net_get_page_callbackâ was here 
net/ipv4/tcp_zero_copy.c:63:1: error: redefinition of â__kstrtab_net_get_page_callbackâ 
net/ipv4/tcp_zero_copy.c:14:1: note: previous definition of â__kstrtab_net_get_page_callbackâ was here 
net/ipv4/tcp_zero_copy.c:63:1: error: redefinition of â__ksymtab_net_get_page_callbackâ 
net/ipv4/tcp_zero_copy.c:14:1: note: previous definition of â__ksymtab_net_get_page_callbackâ was here 
net/ipv4/tcp_zero_copy.c:66:1: error: redefinition of â__kcrctab_net_put_page_callbackâ 
net/ipv4/tcp_zero_copy.c:17:1: note: previous definition of â__kcrctab_net_put_page_callbackâ was here 
net/ipv4/tcp_zero_copy.c:66:1: error: redefinition of â__kstrtab_net_put_page_callbackâ 
net/ipv4/tcp_zero_copy.c:17:1: note: previous definition of â__kstrtab_net_put_page_callbackâ was here 
net/ipv4/tcp_zero_copy.c:66:1: error: redefinition of â__ksymtab_net_put_page_callbackâ 
net/ipv4/tcp_zero_copy.c:17:1: note: previous definition of â__ksymtab_net_put_page_callbackâ was here 
net/ipv4/tcp_zero_copy.c:74:5: error: redefinition of ânet_set_get_put_page_callbacksâ 
net/ipv4/tcp_zero_copy.c:25:5: note: previous definition of ânet_set_get_put_page_callbacksâ was here 
net/ipv4/tcp_zero_copy.c:98:1: error: redefinition of â__kcrctab_net_set_get_put_page_callbacksâ 
net/ipv4/tcp_zero_copy.c:49:1: note: previous definition of â__kcrctab_net_set_get_put_page_callbacksâ was here 
net/ipv4/tcp_zero_copy.c:98:1: error: redefinition of â__kstrtab_net_set_get_put_page_callbacksâ 
net/ipv4/tcp_zero_copy.c:49:1: note: previous definition of â__kstrtab_net_set_get_put_page_callbacksâ was here 
net/ipv4/tcp_zero_copy.c:98:1: error: redefinition of â__ksymtab_net_set_get_put_page_callbacksâ 
net/ipv4/tcp_zero_copy.c:49:1: note: previous definition of â__ksymtab_net_set_get_put_page_callbacksâ was here 
make[2]: *** [net/ipv4/tcp_zero_copy.o] Error 1 
make[1]: *** [net/ipv4] Error 2 
make: *** [net] Error 2 
root@dev01:/usr/src/linux# ls 

Answer 1

这取决于被重复什么，

函数声明重复不会给任何错误。
重复的函数定义会给出错误。
正在创建\定义为相同名称的变量会给出错误。

#2 & #3给出错误，因为他们打破了ODR（一个定义规则）。

void doSomething(); //no error 
void doSomething(); 
void doSomething(); 

void doSomething() 
{ 

} 

int main() 
{ 
    int i; //error 
    int i; 
    doSomething(); 
    return 1; 
} 

在此代码：

net_get_page_callback_t net_get_page_callback __read_mostly; 

限定可变的，并且这样做多次，导致相同的命名变量的多个定义，因而重定义错误。

Answer 2

函数在翻译单元中被多次定义是错误的。这是发生在这里的事情。尝试发布编译中的前几个错误消息。