c++ - 我不明白 [dcl.fct.default]/3 中的最后一句

Question

[dcl.fct.default]/3 (重点是我的):

A default argument shall be specified only in the parameter-declaration-clause of a function declaration or lambda-declarator or in a template-parameter (14.1); in the latter case, the initializer-clause shall be an assignment-expression. A default argument shall not be specified for a parameter pack. If it is specified in a parameter-declaration-clause, it shall not occur within a declarator or abstract-declarator of a parameter-declaration.

上面的最后一句表示，如果在参数声明子句中指定了默认参数，则它不会出现在参数声明的声明符或抽象声明符中。然而，当我查看参数声明的定义时，我在 [dcl.fct]/3 中找到以下内容: (重点是我的):

parameter-declaration:
    attribute-specifier-seqopt decl-specifier-seq declarator
    attribute-specifier-seqopt decl-specifier-seq declarator = initializer-clause
    attribute-specifier-seqopt decl-specifier-seq abstract-declaratoropt
    attribute-specifier-seqopt decl-specifier-seq abstract-declaratoropt = initializer-clause

Answer 1

标准中有脚注

102) This means that default arguments cannot appear, for example, in declarations of pointers to functions, references to functions, or typedef declarations

例如这些声明

void f(void g(int = 10));

void ( *pf )(int = 10);

错了。