c++ - 关于c++1z中[dcl.spec]/3的疑问

Question

[dcl.spec]/3 in c++1z (重点是我的):

If a type-name is encountered while parsing a decl-specifier-seq, it is interpreted as part of the decl-specifier-seq if and only if there is no previous defining-type-specifier other than a cv-qualifier in the decl-specifier-seq. The sequence shall be self-consistent as described below. [ Example:

typedef char* Pc;
static Pc;                      // error: name missing

Here, the declaration static Pc is ill-formed because no name was specified for the static variable of type Pc. To get a variable called Pc, a type-specifier (other than const or volatile) has to be present to indicate that the typedef-name Pc is the name being (re)declared, rather than being part of the decl-specifier sequence.

不过，下面的代码片段无法在 g++ 和 clang 中编译。这是为什么？

typedef char* Pc;
static int Pc;

Answer 1

该段的目的是表明 typedef char* Pc 是有效的，而 static Pc 不是，不是将 Pc 重新声明为其他内容(在同一范围内)。换句话说，static Pc 和static int Pc 不是不同的实体。没有任何更改允许您执行此操作。

[basic.scope.declarative]/4

Given a set of declarations in a single declarative region, each of which specifies the same unqualified name,

(4.1) — they shall all refer to the same entity, ...