“静态常量整数"导致链接错误(未定义引用)

2022-01-05 00:00:00 gcc static constants c++ stdvector

我对使用以下代码时的链接器错误感到困惑:

I am baffled by the linker error when using the following code:

// static_const.cpp -- complete code
#include <vector>

struct Elem {
    static const int value = 0;
};

int main(int argc, char *argv[]) {
    std::vector<Elem> v(1);
    std::vector<Elem>::iterator it;

    it = v.begin();
    return it->value;
}

然而，这在链接时会失败――不知何故，它需要有一个代表静态常量值"的符号.

However, this fails when linking -- somehow it needs to have a symbol for the static const "value."

$ g++ static_const.cpp 
/tmp/ccZTyfe7.o: In function `main':
static_const.cpp:(.text+0x8e): undefined reference to `Elem::value'
collect2: ld returned 1 exit status

顺便说一句，这在 -O1 或更好的情况下编译得很好；但对于更复杂的情况，它仍然失败.我使用的是 gcc 版本 4.4.4 20100726 (Red Hat 4.4.4-13).

BTW, this compiles fine with -O1 or better; but it still fails for more complicated cases. I am using gcc version 4.4.4 20100726 (Red Hat 4.4.4-13).

知道我的代码可能有什么问题吗?

Any ideas what might be wrong with my code?

推荐答案

如果你想在 struct 内部初始化它，你也可以这样做:

If you want to initialize it inside the struct, you can do it too:

struct Elem {
    static const int value = 0;
};

const int Elem::value;

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