RTTI support for C++11 ( _CPPRTTI and __GNUG__ )

Question

I am updating some old C++ code.

I've come across the following:

    #if defined( _CPPRTTI ) || defined( __GNUG__ )
            const char* default_name{ (typeid(FooClass)).name() };
    #else
            const char* default_name{ "unknown" };
    #endif

RTTI is Run-Time Type Information, it looks as though it is dealing with certain compilers that did't support typeid().

But this code is > 15 years old.

Can one assume that RTTI support is in place for C++11?

Answer 1

Some compilers allow you to disable support for RTTI at compile-time. For example, see Visual C++'s /GR- and GCC's -fno-rtti.

If you don't use RTTI in your program (typeid, dynamic_cast, etc.) then disabling RTTI at compile-time may substantially reduce the size of the final binary.