RFA: libiberty: Fix infinite recursion in rust demangler (PRs 98886 and 99935)

[Jeff Law]

On 1/26/2022 8:29 AM, Nick Clifton via Gcc-patches wrote:
> Hi Guys,
>
>    I would like to propose the patch below to fix a couple of sources
>    of infinite recursion in libiberty's rust demangling code.  This patch
>    is based upon the one submitted for PR 99935, but extended to cope
>    with the case presented in PR 98886 and also fixed so that the "uint"
>    type is not used.
>
>    Tested with a patched version of the binutils sources on an
>    x86-pc-linux-gnu target.
>
> Cheers
>    Nick
>
> 2022-01-26  Nick Clifton  <nickc@redhat.com>
>
> 	* rust-demangle.c (struct rust_demangler): Add a recursion
> 	counter.
> 	(demangle_path): Increment/decrement the recursion counter upon
> 	entry and exit.  Fail if the counter exceeds a fixed limit.
> 	(demangle_type): Likewise.
> 	(rust_demangle_callback): Initialise the recursion counter,
> 	disabling if requested by the option flags.
OK.  I'm both amazed and disappointed at how all the demanglers seem to 
be prone to infinite recursion.

jeff