On Wednesday 13 November 2013 12:44:54 Niall Douglas wrote:
On 13 Nov 2013 at 14:28, Antony Polukhin wrote:
* const char* name() // same as std::type_info::name() * const char* raw_name() // mangled/short/not very readable name * std::string pretty_name() // was name_demangled()
Looks great to me.
I like it too. Now it is a drop in replacement that supports even the MSVC extensions.
I'm afraid I disagree - you're breaking the interface contract with std::type_info when RTTI is off.
Previous commenters may not realise that template_info::name() does NOT return the same value as type_info::name() when RTTI is off. It returns an internal unique const char * value, that's all.
AFAIR, std::type_info::name() gives no guarantees of the returned string contents whatsoever. I don't see why boost::type_info::name() should offer anything more. Also, I don't think it has to return the same string with and without RTTI enabled.
My concern is that MSVC's raw_name() does something very explicit: if you read http://msdn.microsoft.com/en-us/library/vstudio/70ky2y6k.aspx, it explicitly says that raw_name() specifically returns the mangled ("decorated") form of the type expression. TypeIndex, with RTTI off, would not return such a string for its raw_name().
I do not see why boost::type_info::raw_name() should have semantics equivalent to MSVC std::type_info::raw_name(), especially since the latter is non- standard. We can implement boost::type_info::raw_name() in terms of MSVC std::type_info::raw_name(), but we surely cannot guarantee that it will always return what MSVC std::type_info::raw_name() does, on other compilers. This is the reason I objected against name_demangled() naming. In my view, boost::type_info::raw_name() should be described as a function returning an implementation-defined string that may be equivalent to boost::type_info::name() but, if possible, may be in a platform-specific mangled format. FWIW, boost::type_info interface description should allow to implement name(), raw_name() and pretty_name() all the same way - based on std::type_info::name() or another adequate source of strings in the lack of native RTTI.
Regarding the problem of name() compatibility: it is deeply unfortunate that MSVC chose that name() should be demangled, while everyone else chose that name() should be mangled. It means you see this everywhere which uses type_info:
#ifdef _MSC_VER ti.raw_name() #else ti.name() #endif
A little irrelevant, but I personally don't think MSVC choice was wrong. I'd prefer std::type_info::name() to return a human readable string on most compilers instead of having to write hacks like __cxa_demangle().
One of the things I really like about boost::type_info is that we do away with this silliness and name() always means "the shortest unique representation string" on every platform.
Again, std::type_info::name() does not have that meaning and there is no reason for boost::type_info::name() to have it. boost::type_info::name() should be exactly what it advertises itself - an equivalent for std::type_info::name(). For any other preference you should be using boost::type_info::raw_name() or boost::type_info::pretty_name().
Can I suggest this instead: instead of making boost::type_info more like the flawed std::type_info, can you leave boost::type_info to be pure and instead add a new boost::type_info_std or something which does replicate std::type_info's implementation specific quirks?
I don't see the point in such duplication. boost::type_index will only work with boost::type_info anyway.