C++: noexcept

整理自 C++ Primer, 5th Edition

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1. noexcept == throw()

void recoup(int) noexcept;	// recoup doesn't throw
void recoup(int) throw();	// equivalent declaration

2. Violating the Exception Specification

It is important to understand that the compiler does not check the noexcept specification at compile time.

// this function will compile, even though it clearly violates its exception specification
void f() noexcept {
	throw exception(); // violates the exception specification
}

But if a noexcept function does throw, terminate is called to exit the program.

3. Arguments to the noexcept Specification

void recoup(int) noexcept(true);	// recoup won't throw
void alloc(int) noexcept(false);	// alloc can throw

4. The noexcept Operator

noexcept(e) 

// Is true if all the functions called by e have non-throwing specifications and e itself does not contain a throw. 
// Otherwise, returns false.

We can use the noexcept operator to form an exception specifier as follows:

void f() noexcept(noexcept(g()));

相当于就是 “You throw. I throw.”

5. Exception Specifications for Copy Control Members

When the compiler synthesizes the copy-control members, it generates an exception specification for the synthesized member.

• If all the corresponding operation for all the members and base classes promise not to throw, then the synthesized member is noexcept.
• If any function invoked by the synthesized member can throw, then the synthesized member is noexcept(false).