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Re: [PATCH] Set DEMANGLE_RECURSION_LIMIT to 1536
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: Jason Merrill <jason at redhat dot com>, Michael Matz <matz at suse dot de>, Nick Clifton <nickc at redhat dot com>, Ian Lance Taylor <iant at google dot com>, "H.J. Lu" <hjl dot tools at gmail dot com>, Pedro Alves <palves at redhat dot com>, Richard Biener <richard dot guenther at gmail dot com>, Scott Gayou <sgayou at redhat dot com>, Tom Tromey <tom at tromey dot com>, gcc-patches List <gcc-patches at gcc dot gnu dot org>, Binutils <binutils at sourceware dot org>
- Date: Tue, 11 Dec 2018 07:58:04 +0100
- Subject: Re: [PATCH] Set DEMANGLE_RECURSION_LIMIT to 1536
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- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Mon, Dec 10, 2018 at 05:33:19PM -0700, Jeff Law wrote:
> >> where di.num_comps is just strlen (mangled) * 2. Without any analysis
> >> whatsoever, bumping the "recursion" limit will just mean we can process 1.5
> >> times long names. Either we need more precise analysis on what we are
> >> looking for (how big arrays we'll need) or it needs to be an independent
> >> limit and certainly should allow say 10KB symbols too if they are
> >> reasonable.
> > If the problem is alloca, we could avoid using alloca if the size
> > passes a threshold. Perhaps even use a better data structure than a
> > preallocated array based on a guess about the number of components...
> Actually I would strongly suggest avoiding alloca completely. This
> isn't particularly performance sensitive code and alloca can be abused
> in all kinds of interesting ways.
We can't use malloc, therefore on some targets alloca (or VLAs) are the only
option, and for small sizes even if mmap is available using it is too
Though, I like Jason's suggestion of just adding a maxinum of the number
of components and number of substitutions and failing if we need more.