Including an exception class in a header file

Question

I have a pair of files, say Foo.cpp and Foo.hpp that define a class, say Foo . Foo 's methods have the potential to throw an exception, defined in the file MyException.hpp , but Foo.hpp does not need MyException .

Obviously the .cpp needs to include the exception header, but should I include the exception header in Foo.hpp instead to allow any files that use Foo to have a definition of the exception?

Answer 1

The usual rule of thumb is that every file should include the headers that it needs. So, no, don't add MyException.hpp to Foo.hpp unless it's needed there. Code that deals with your exception class should #include "MyException.hpp" . So, obviously, whichever files implement the member functions that throw this exception need to include "MyException.hpp" , and any files that include code that catch this exception also need it.

Answer 2

I assume you derive your custom exception from std::exception.

Now there are two use cases (I imagine):

• The exception is informative, nothing can be done to resolve it. Hence nobody will care about the actual type (you may keep it the source).
• The exception is specific and an action can resolve it: Make the exception type public in the header.

Most of the exceptions I have seen are informative, there is nothing to resolve the state of objects affected.

Answer 3

It is considered a good style to make each .h file self-sufficient , so that each header would include/provide all features it needs. Given that, it makes sense to include MyException.hpp in Foo.hpp . That way, users of Foo.h will not endure compile-time errors when they just include it in their code.

Answer 4

Only include the MyException.hpp header in you Foo.hpp file. Let your Foo.cpp include only the Foo.hpp header. The .cpp file is only meant for the implementation of the interface declared in the header file. The .cpp should not contain any other includes part from it's own header.