警告：“索引”的声明隐藏了全局声明 [英] warning: declaration of 'index' shadows a global declaration

问题描述

我的编译器（GCC）正显示出警告

My Compiler(gcc) is showing the warning

警告：索引的声明隐藏了全局声明

warning: declaration of 'index' shadows a global declaration

请帮助我了解为什么这个发出警告。

Please help me understand why this warning comes.

推荐答案

当你做的东西像它的：

int index;
int main (void) {
    int index;
    ....
    return 0;
}

什么它是警告的是，在首页在的main（）实际上是隐藏全局的在你面前的main（）。

What it's warning about is that the index inside main() is actually hiding the global one you've declared before main().

这是警告你，你不能在全局定义，同时获得当地的一个是积极的。现在，这不是的不一定的问题（因此它只是一个警告），这是完全合法的C，但是你需要知道的可能后果。

It's warning you that you can't get at the global definition while the local one is "active". Now that's not necessarily a problem (hence why it's only a warning), it's perfectly valid C, but you need to be aware of the possible consequences.

顺便说一句，一些C实现（基于BSD）定义了一个首页的功能的 string.h中其也可造成问题。这个功能的使用pcated德$ P $，它不会在C标准的出现（使用和strchr 代替），但也可能是问题的原因，如果你上运行（例如）的Mac OS或OpenBSD的（下的#define 设置一些组合甚至是Linux的，我相信）。

As an aside, some C implementations (BSD-based) define an index function in string.h which may also cause a problem. Use of this function is deprecated and it doesn't appear in the C standard (use strchr instead) but it may be the cause of problems if you're running on (for example) Mac OS or OpenBSD (or even Linux under some combination of #define settings, I believe).

有几种方法来解决这个问题（如果需要）。

There are a couple of ways to get around this (if you need to).

首先大概是preferred一：不的使用的全局。是的，这是正确的，摆脱他们。他们很少需要，所以不要让我过来和周围掌掴你： - ）

The first is probably the preferred one: don't use globals. Yes, that's right, get rid of them. They're very rarely needed so don't make me come over and slap you around :-)

我见过的第二种方法是，以确保他们打包。假设你实际的需求的全局（绝不是板上钉钉的事情，见previous段），创建一个保存他们的结构，如在以下几点：

A second way I've seen is to ensure they're "packaged". Assuming that you actually need globals (by no means a certainty, see previous paragraph), create a structure that holds them, such as in the following:

myglobs.h:
    struct sMyGlobs {
        int index;
        // all other globals.
    };
    extern struct sMyGlobs myGlobs;

myglobs.c:
    #include "myglobs.h"
    struct sMyGlobs myGlobs;

main.c:
    #include <stdio.h>
    #include "myglobs.h"
    int main (void) {
        myGlobs.index = 42;
        return 0;
    }

这有它的明显，你指的是一个全球性的优势，那他们永远隐藏的，除非你做类似定义一个名为自己的本地变量 myGlobs 。

This has the advantage in that it's obvious that you're referring to a global and that they're never hidden, unless you do something like define your own local variable called myGlobs.

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