On Mon, Dec 10, 2018 at 10:10 AM Jakub Jelinek <ja...@redhat.com> wrote: > On Mon, Dec 10, 2018 at 02:52:39PM +0000, Michael Matz wrote: > > On Fri, 7 Dec 2018, H.J. Lu wrote: > > > > > > > On Thu, Dec 6, 2018 at 3:12 AM Nick Clifton <ni...@redhat.com> wrote: > > > > > > > > > > > > Is the patch OK with you ? > > > > > > > > > > > > > This caused: > > > > > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88409 > > > > > > > > > > Here is the fix. OK for trunk? > > > > I think this points toward the limit being _much_ too low. With template > > meta programming you easily get these mangled names, it's not even a > > particularly long one. But I'm wondering a bit, without tracing the > > demangler, just looking at the symbol name and demangled result I don't > > readily see where the depth of recursion really is more than 1024, are > > there perhaps some recursion_level-- statements skipped? > > That is because the recursion_level limit isn't hit in this case at all (far > from it). > > What breaks it is this: > > /* PR 87675 - Check for a mangled string that is so long > that we do not have enough stack space to demangle it. */ > if (((options & DMGL_NO_RECURSE_LIMIT) == 0) > /* This check is a bit arbitrary, since what we really want to do is to > compare the sizes of the di.comps and di.subs arrays against the > amount of stack space remaining. But there is no portable way to do > this, so instead we use the recursion limit as a guide to the maximum > size of the arrays. */ > && (unsigned long) di.num_comps > DEMANGLE_RECURSION_LIMIT) > { > /* FIXME: We need a way to indicate that a stack limit has been > reached. */ > return 0; > }
> 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... Jason
