c++ - C++ 标准中 7.1.6.1/1 中的这条语句有什么相关性？

Question

7.1.6.1/1 包含以下声明(强调我的):

There are two cv-qualifiers, const and volatile. If a cv-qualifier appears in a decl-specifier-seq, the init-declarator-list of the declaration shall not be empty.

上面加粗的语句有什么相关性？换句话说，是否有可能在 decl-specifier-seq 中生成一个 cv-unqualified 类型的示例，其中 init-declarator-list 的声明是空的？

Answer 1

当然，大多数类和枚举定义都使用它:

struct A { }; // valid
const struct B { }; // invalid, const would have no meaning
const struct C { } c { }; // valid

没有别的了。 init-declarator-list 仅用于简单声明，为此，标准 (C++11) 规定:

7 Declarations [dcl.dcl]

3 In a simple-declaration, the optional init-declarator-list can be omitted only when declaring a class (Clause 9) or enumeration (7.2), that is, when the decl-specifier-seq contains either a class-specifier, an elaborated-type-specifier with a class-key (9.1), or an enum-specifier.