Question 2: In actual fact most of the classes in our code follow a common protocol, so you could reasonably ask for quite a few members you could expect to be there. I won’t go into proprietary details, but obviously each class has a name, and you can imagine that certain classes would have a property where every instance would have a globally-unique canonical human-readable identifier, which would be nice to have in the log.

Question 3: I’m not sure I follow. I was anticipating a global logging function (probably an ostream actually) that can log whatever’s passed to it, and class-local adapters that would package up instance-specific information and pass it to the generic logging code. The packing-up code would have to be duplicated to some extent.

I’m not sure the duplication’s as bad as I thought – I think you can play games with covariant return types and the Curiously Recurring Template Pattern that will avoid the need for downcasting. I’m afraid the latter half of this post was rather rushed and lost its coherence, and I’m sufficiently tired that I don’t feel like going back and fixing things. I might write another post about CRTP at some point though.

However, you can get closer to the ideal output.

You can use template specialisation to name common types, e.g.


template string TypeDecryptor::getName (void) { return "int"; }
template string TypeDecryptor<MyClass >::getName (void) { return "MyClass"; }


You can also add per-toolchain support for demangling, e.g.


#if __GXX_ABI_VERSION > 1000
#include
template string TypeDecryptor::getName (void)
{
int s;
char *b (abi::__cxa_demangle (typeid (T).name (), NULL, NULL, &s));
//if (!b || s) throw ...;
return b;
}
#else
template string TypeDecryptor::getName (void) { return typeid (T).name (); }
#endif


boost::units::detail::demangle does pretty much this.

Of course actually doing any of this is a pain in the ass.

Using a static object to describe the type desired (Like, using a size object to define a fixed-size 2-d array, instead of giving two int parameters (?). Or using a string to give a class type a name at compile type, if for some reason the built in name or a static variable don’t work (?)).

Having a class which relates to a specific object (eg. a multi-gigabyte-size class which you allocate just one one and have some classes which only ever refer to that particular instantiation (?)).

Although I don’t know if they’re even valid

http://www.codesharp.co.uk/dvorak/