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Re: Two issues with stack overflow protection

From: Paul Eggert
Subject: Re: Two issues with stack overflow protection
Date: Tue, 28 Jul 2015 22:01:55 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0

Eli Zaretskii wrote:
The implementation of stack_overflow on sysdep.c was recently changed
so as not to use sys/resource.h and getrlimit, but configure.ac still
insists on these two features in order to include the recovery code,
which I think should be fixed.

Thanks, fixed with the attached patch.

More importantly, the recovery simply longjmps to command_loop,
whereas similar features like Fthrow and Fsignal do much more in
unwind_to_catch.  Shouldn't stack overflow recovery do that as well?
Otherwise, the specpdl stack, byte_stack_list, lisp_eval_depth
etc. all stay at their values they had at stack overflow time, no?

No, they are cleared back to top-level values, because when command_loop's call to sigsetjmp returns nonzero, it then calls init_eval and this resets them.

There is a problem that the speclpdl stack's unwind-protect and dynamic-let-bindings are unceremoniously discarded on stack overflow. I suppose that should get fixed, though it may be a bit tricky to avoid looping.

Attachment: 0001-Remove-unnecessary-stack-overflow-dependency.patch
Description: Text Data

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