Re: Possible memory corruption problem

[Aidan Kehoe]

 Ar an ceathrú lá déag de mí Feabhra, scríobh Piet van Oostrum: 

 > >>> Emacs tries to estimate how much memory is available, but that estimate
 > >>> may not really work.  For instance, it never works for me.
 > >>> The code to estimate available space worked in the 80s on Unix,
 > >>> but it may need adaptation to the systems of today.

Ben Wing implemented this in XEmacs by looking at what getrlimit(2) returns,
which is effective and consistent with what modern OSes do. He also
abstracted it to fall back to ulimit if that’s not available, or to use the
Win32-specific procedure when that’s appropriate. 

 > >EZ> It's possible that the existing estimate doesn't work on systems that
 > >EZ> don't use sbrk.  I believe GNU/Linux is one of those systems.
 > 
 > It seems it is not used on Mac OS X either. The man page says:
 >      The brk and sbrk functions are historical curiosities left over from
 >      ear- lier days before the advent of virtual memory management.
 > 
 > And I run a test program with malloc calls, set a breakpoint at brk and
 > sbrk and it did not reach those.

Which is well and good; implementing a heap using mmap, for example, means
you can release memory back to the OS once it’s been freed. 

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