extern const数组声明/初始化错误（初始化程序/ conlficting类型无效）

Question

对于我正在研究的项目，我想要一个静态初始化的，不可变的全局数组 - 特别是数组，而不是enum。据我所知，最好的方法是使用extern const数组。但是，当我尝试初始化并声明任何数组foo时，我得到两个不同但显然相关的编译器错误：

error: conflicting types for `foo'
error: invalid initializer

对于我的.c文件的外部范围中的每次初始化，都会重复这些操作。前面的这些错误总是后跟一个注释“previous declaration of `foo' was here”，并指向头文件中数组的声明。

在以下示例中......

#ifndef __MWE__
#define __MWE__

extern const int foo[8];

#endif /* MWE */

#include "mwe.h"
const int foo[0] = 0;
const int foo[1] = 42;
const int foo[2] = 69;
const int foo[3] = 420;
const int foo[4] = 9001;


int main(int argc,char**argv){return 0;}

......我收到以下错误......

mwe.c:3:11: error: conflicting types for ‘foo’
 const int foo[0] = 0;
           ^~~
In file included from mwe.c:1:0:
mwe.h:4:18: note: previous declaration of ‘foo’ was here
 extern const int foo[5];
                  ^~~
mwe.c:3:20: error: invalid initializer
 const int foo[0] = 0;
                    ^
mwe.c:4:11: error: conflicting types for ‘foo’
 const int foo[1] = 42;
           ^~~
In file included from mwe.c:1:0:
mwe.h:4:18: note: previous declaration of ‘foo’ was here
 extern const int foo[5];
                  ^~~
mwe.c:4:20: error: invalid initializer
 const int foo[1] = 42;
                    ^~
mwe.c:5:11: error: conflicting types for ‘foo’
 const int foo[2] = 69;
           ^~~
In file included from mwe.c:1:0:
mwe.h:4:18: note: previous declaration of ‘foo’ was here
 extern const int foo[5];
                  ^~~
mwe.c:5:20: error: invalid initializer
 const int foo[2] = 69;
                    ^~
mwe.c:6:11: error: conflicting types for ‘foo’
 const int foo[3] = 420;
           ^~~
In file included from mwe.c:1:0:
mwe.h:4:18: note: previous declaration of ‘foo’ was here
 extern const int foo[5];
                  ^~~
mwe.c:6:20: error: invalid initializer
 const int foo[3] = 420;
                    ^~~
mwe.c:7:11: error: conflicting types for ‘foo’
 const int foo[4] = 9001;
           ^~~
In file included from mwe.c:1:0:
mwe.h:4:18: note: previous declaration of ‘foo’ was here
 extern const int foo[5];
                  ^~~
mwe.c:7:20: error: invalid initializer
 const int foo[4] = 9001;

声明和初始化extern const数组的正确方法是什么，以及这种无效的方式是什么？类型冲突在哪里，为什么整数文字对于整数数组的元素是无效的初始值设定项？

Answer 1

每个：

const int foo[0] = 0;
const int foo[1] = 42;
const int foo[2] = 69;
const int foo[3] = 420;
const int foo[4] = 9001;

是名为foo的数组变量的单独定义，每个变量具有不同的大小。您还尝试使用单个值初始化这些数组。这就是你得到错误的原因。

如果要初始化数组，请执行以下操作：

const int foo[5] = { 0, 42, 69, 420, 9001 };

如果需要基于枚举值初始化特定索引，可以使用指定的初始值设定项来执行此操作：

enum {
    E1, E2, E3, E4, E5
};
const int foo[5] = { 
    [E1] = 0, 
    [E2] = 42, 
    [E3] = 69, 
    [E4] = 420, 
    [E5] = 9001 
};