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

Ian Lance Taylor ian@airs.com
Thu Nov 29 22:18:00 GMT 2018 
Pedro Alves <palves@redhat.com> writes:

> 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.)

I agree.  Using static variables here seems problematic.  Right now as
far as I know the demangler has no static variables at all.

Ian
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