c++ - extern数组出现 undefined reference 错误，但对于int效果很好

Question

编译错误:
[build] main.cpp:8:未定义对`pallete'的引用

示例代码:
common.cpp

const unsigned char pallete[] = {0, 60, 100, 119};
int a = 1;

main.cpp

#include <iostream>

extern const unsigned char pallete[];
extern int a;

int main() {
    std::cout << a << std::endl;
    std::cout << pallete[0] << std::endl;
    return 0;
}

Answer 1

您必须在extern中声明pallete common.cpp。现在main.cpp知道应该在单独的文件中“查找”货盘，但是common.cpp将其视为本地文件，因为它是const，如此处https://en.cppreference.com/w/cpp/language/cv#Notes

Notes

The const qualifier used on a declaration of a non-local non-volatile non-template (since C++14)non-inline (since C++17) variable that is not declared extern gives it internal linkage. This is different from C where const file scope variables have external linkage.

extern const unsigned char pallete[] = {0, 60, 100, 119};
int a = 1;