C++，函數指針異常錯誤

Question

使用下面的代碼，我得到「錯誤：超出單一間接級別的異常規範」。請給我一個參考書/規範，說它不被允許。我想確定它確實是語言所必需的，或者只是編譯器特定的錯誤。如果從語言規範來看，這個規則是什麼動力？我使用的是鏗鏘3.8.0。

int main() 
    { 
     void (**fp)() throw() ; 
    } 

Answer 1

你說：

Please point me to a reference book /spec that says that it is not allowed. I want to be sure that it is really required by the language or just compiler specific error.

隨着

void (**fp)() throw() ; 

你想在一個指向函數指針的聲明指定一個異常規範。這是標準所不允許的。 例外規範僅適用於有限的一組聲明。

從https://timsong-cpp.github.io/cppwp/n3337/except.spec#2（重點煤礦）：

An exception-specification shall appear only on a function declarator for a function type, pointer to function type, reference to function type, or pointer to member function type that is the top-level type of a declaration or definition, or on such a type appearing as a parameter or return type in a function declarator. An exception-specification shall not appear in a typedef declaration or alias-declaration. [ Example:

void f() throw(int);     // OK 
void (*fp)() throw (int);    // OK 
void g(void pfa() throw(int));   // OK 
typedef int (*pf)() throw(int);   // ill-formed 

— end example ] A type denoted in an exception-specification shall not denote an incomplete type. A type denoted in an exception-specification shall not denote a pointer or reference to an incomplete type, other than void* , const void* , volatile void* , or const volatile void* . A type cvT , 「array of T 」, or 「function returning T 」 denoted in an exception-specification is adjusted to type T , 「pointer to T 」, or 「pointer to function returning T 」, respectively.

---

你問：

If it is from language specification, what motivates this rule?

我沒有一個答案。