C++ Do I need to write throw clause for a function

问题:

Before

Consider to have a class and a global function:

This is, for example, usefulfuncts.hpp

void dosome(int a, int b) throw (std::exception);

This is usefulfuncts.cpp

void dosome(int a, int b) throw (std::exception) {
   //...
}

And this is aclass.hpp

class aclass {
   // Members...
   friend void dosome(int a, int b) throw (std::exception);
   // Members...
};

After (what I would like that to be)

Ok! I would like to understand if it is strictly necessary to write everytime the throw clause. So for example can I do this?

This is usefulfuncts.hpp

void dosome(int a, int b) throw (std::exception);

This is usefulfuncts.cpp

void dosome(int a, int b) { /* OMITTING IT! */
   //...
}

And this is aclass.hpp

class aclass {
   // Members...
   friend void dosome(int a, int b); /* OMITTING IT */
   // Members...
};

Is this right? To put it only in the main declaration? Thanks

回答1:

Omitting a exception specification means that your function can throw any exception.

Exceptions specifications are bad. There are hardly any compilers which implement the feature correctly. They have been deprecated since the C++11 Standard. In fact Exception specifications were considered a failed experiment even while they were a part of the C++03 standard.

Good Read:
A Pragmatic Look at Exception Specifications

回答2:

Declaring exceptions is a bad idea. From http://www.gotw.ca/publications/mill22.htm :

Moral #1: Never write an exception specification.
Moral #2: Except possibly an empty one, but if I were you I’d avoid even that.

回答3:

Exception specifications are deprecated in C++11 - do not write exception specifications unless it is to specify that your function is guaranteed not to throw an exception.

Note that actually providing this guarantee is harder than it may seem - Herb Sutter has written many articles and a book on the subject of exceptions and exception safety.