c++ - 关于静态局部变量的说明

Question

在链接中 Storage Class Specifier

在主题静态局部变量下我读过

Variables declared at block scope with the specifier static have static storage duration but are initialized the first time control passes through their declaration (unless their initialization is zero- or constant-initialization, which can be performed before the block is first entered).

我不明白说:

到底是什么意思

which can be performed before the block is first entered

另外，是否可以说static 局部变量具有No Linkage？

如有必要，您能举一些例子吗？谢谢

Answer 1

相关部分是当初始值已知时。
当知道在 block 第一次执行之前它不会改变的额外保证。

下面是带有一些示例的代码。

int foo(void);

void bar(void)
{
    static int ZeroInit;     // zero init
    static int a = 0;        // constant init
    static int b = 4;        // constant init
    // values for above inits are known at start of runtime and even earlier

    static int c = foo();
    // dynamic init, value unknown before execution of foo(),
    // which cannot (i.e. is defined not to) be done before executing the block

    /* code */
}