Re: Incorrect demangling

[Alan Barrett <apb%cequrux.com@localhost>]

On Tue, 24 Apr 2012, Rich Neswold wrote:
> My "C++ Programming Reference, 2nd edition" (1994), section 
> r.2.4 says:
>
> "In addition, identifiers containing a double underscore (__) 
> are reserved for use by C++ implementations and standard 
> libraries and should be avoided by users."

That's in the C++ reference manual, so "users" should be 
understood to mean "users of the C++ language".  The C++ reference 
manual should have no jurisdiction over users of languages other 
than C++.

Users of the C language should be able to find everything they 
need in the C reference manual and associated library reference 
manuals, plus the implementation-specific documentation (e.g. the 
compiler manual) if they rely on implementation-specific features 
of the language.  Section 7.1.3 of the N1256 draft of the C2010 
standard provides a list of rules for determining whether an 
identifier is reserved, and double underscore is featured only 
when it appears at the beginning of an identifier.  The same 
clause also says "No other identifiers are reserved", so it seems 
pretty clear to me that identifiers that contain double underscore 
are not reserved in the C language (unless they also hit one of 
the other restrictions).

> So it looks like you won't convince the GCC maintainers in 
> changing the compiler. Plus, PCC and CLANG will probably give 
> you similar problems.

It looks as though anything that performs demangling should 
have some way other than the symbol name of figuring out whether 
the symbol came from C++, so that it is not tripped up by valid C 
symbols that happen to mean something special when viewed as C++
symbols.

--apb (Alan Barrett)