Re: Bug#245678: zsh: built-in rm -rf fills up the memory

[Peter Stephenson <pws@csr.com>]

Bart Schaefer wrote:
> } [ h->used + (new - old) > HEAP_ARENA_SIZE ]
> } 63432 + (63504 - 63432) > 16360
> 
> Aha!  Note that h->used > HEAP_ARENA_SIZE all by itself!
> 
> Comparing to HEAP_ARENA_SIZE is likely wrong, it should compare to the 
> maximum of either HEAP_ARENA_SIZE or the previously-mmapped page size.
> I'm not entirely sure of that ...
> 
> ... but that's why it begins re-zhalloc()-ing.  In the non-MMAP case it
> falls back on realloc() when a single allocation exceeds HEAP_ARENA_SIZE.
> 
> So what probably needs to happen to prevent the out-of-memory condition
> is that we need to explicitly munmap the old mmap'd block, somewhere.
> 
> And then we need to emulate realloc() behavior somehow, in terms of
> knowing whether to actually re-mmap-and-copy or whether the existing
> mapped pages are large enough to contain the additional requested space.

Looks like a rewrite of hrealloc is definitely in order...

Does the bad behaviour go away if USE_MMAP is undefined?

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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