user stack support for TMP_ALLOC

[Torbjorn Granlund]

Bill Allombert <allomber at math.u-bordeaux.fr> writes:

  The only issue we have with this multiprecision kernel is the alloca stack
  overflow problem.
  
We are changning the use of alloca for GMP 5.  It will never allocate large
chunks on the stack.  That change should make the stack usage very small.
  
  I have written a patch [snip]

I am unfortunately rejecting your patch.  Some usages of alloca in GMP are
too critical for going through a mechanism such as the one you are
proposing.

-- 
Torbjörn