Author: Petr Pisar Date: To: pcre-dev Subject: Re: [pcre-dev] [Bug 1642] Tests fail due to stack space being
limited to 16 M
On Mon, Jun 15, 2015 at 08:15:59AM +0100, ph10@??? wrote: > On Mon, 15 Jun 2015, admin@??? wrote:
>
> > Would it be possible to change the recursion limit from number of calls to
> > amount of memory? This would eliminate the wild guess of how many memory a call
> > needs.
>
> As far as I know, there is no standard (OS-independent) way of finding
> out, from within a C program, anything about the amount of memory
> available on either the stack or the heap.
> My proposal was to to measure number of consumed stack. Instead of adding
1 to a counter on each call, one would compute difference of stack pointer at
current call to the first call and compared this delta to the limit. You could
do it even without in-line assembler simply by referencing an
automatic-storage variable like a variable local to the current function. Of
course there would be some off-by-one-call drift but that could be ignored or
extrapolated based on current stack usage growth ratio.
Your remark gave me an idea that the size of the stack could be obtained by
getrlimit() on the first call, so even the user would not need to specify the
limit explicitly as the default would be that (minus stack consumed by a PCRE
application on the first call). That would provide fully automatic heuristic
preventing from unexpected sefgaults.
