In short (full story provided by links in the splash’s answer): {$RTTI EXPLICIT METHODS([]) PROPERTIES([]) FIELDS([])} Note that as of XE6 and newer, this needs to be in each individual unit for which you want to disable RTTI. Before that (XE5 and below) it could be in the DPR file and would apply to all … Read more
Clone method There is nothing provided by the language that queries type and lets you construct from that information, but you can provide the capability for your class hierarchy in various ways, the easiest of which is to use a virtual method: struct Base { virtual ~Base(); virtual std::auto_ptr<Base> clone(/*desired parameters, if any*/) const = … Read more
Acyclic Visitor (pdf) is a great use of it.
There are several reasons why LLVM rolls its own RTTI system. This system is simple and powerful, and described in a section of the LLVM Programmer’s Manual. As another poster has pointed out, the Coding Standards raises two major problems with C++ RTTI: 1) the space cost and 2) the poor performance of using it. … Read more
Does it matter which is faster, if they don’t do the same thing? Comparing the performance of statements with different meaning seems like a bad idea. is tells you if the object implements ClassA anywhere in its type heirarchy. GetType() tells you about the most-derived type. Not the same thing.
You don’t need RTTI. Any code has implicit access to the protected members of any class declared in the same unit. You can take advantage of this by declaring a new TWinControl descendant in the unit that needs access to that class’s members. The declaration is very simple: type TProtectedWinControl = class(TWinControl); Then type-cast any … Read more
dynamic_cast works only on polymorphic types, i.e. classes containing virtual functions. In gcc you can dynamic_cast to void* but not from: struct S { virtual ~S() {} }; int main() { S* p = new S(); void* v = dynamic_cast<void*>(p); S* p1 = dynamic_cast<S*>(v); // gives an error }
Discontiguous enumerations, and enumerations which don’t start at zero, don’t have typeinfo. For typeinfo to be implemented, it would need to be in a different format from the existing tkEnumeration, owing to backward compatibility issues. I considered implementing a tkDiscontiguousEnumeration (or possibly better named member) for Delphi 2010, but the benefit seemed small considering their … Read more
Regardless of compiler, you can always save on runtime if you can afford to do if (typeid(a) == typeid(b)) { B* ba = static_cast<B*>(&a); etc; } instead of B* ba = dynamic_cast<B*>(&a); if (ba) { etc; } The former involves only one comparison of std::type_info; the latter necessarily involves traversing an inheritance tree plus comparisons. … Read more
The return of name is implementation defined : an implementation is not even required to return different strings for different types. What you get from g++ is a decorated name, that you can “demangle” using the c++filt command or __cxa_demangle.