Fix fir PR71696 in Libiberty Demangler (6)

[Bernd Schmidt]

On 06/30/2016 08:46 AM, Marcel Böhme wrote:
> The attached patch fixes the stack overflow in the demangler due to
> cycles in the references of “remembered” mangled types
> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71696).
>
> The methods demangle_signature and do_arg in cplus-dem.c allow to
> “remember” mangled type names that can later be referenced and will
> also be demangled. The method demangle_args demangles those types
> following any references. So, if there is a cycle in the referencing
> (or in the simplest case a self-reference), the method enters
> infinite recursion.
>
> The patch tracks the mangled types that are currently being demangled
> in a new variable called work->proctypevec. If a referenced type is
> currently being demangled, the demangling is marked as not
> successful.

I'll defer reviewing these to someone who understands demangling better. 
You might want to Cc Jason.


Bernd