Re: RFA/RFC: Add stack recursion limit to libiberty's demangler

[Pedro Alves <palves@redhat.com>]

Hi Nick,

On 11/29/2018 03:01 PM, Nick Clifton wrote:
>  static struct demangle_component *
>  d_function_type (struct d_info *di)
>  {
> -  struct demangle_component *ret;
> +  static unsigned long recursion_level = 0;

Did you consider making this be a part of struct d_info instead?
IIRC, d_info is like a "this" pointer, passed around pretty
much everywhere.

I think going in the direction of making the demangler harder to use
in an efficient thread-safe manner is undesirable, even if the feature
is optional.  E.g., in GDB, loading big binaries, demangling is very high
in profiles, and so we've kicked around the desire to parallelize
it (e.g., by parallelizing the reading/interning of DSO files, instead of
reading all of them sequentially).  Having to synchronize access to the
demangler would be quite unfortunate.  If possible, it'd be great
to avoid making work toward that direction harder.  (Keeping in mind that
if this recursion detection feature is useful for binutils, then it should
also be useful for GDB.)

Thanks,
Pedro Alves