Configure fails on 32-bit platform

[Torbjörn Granlund]

Vincent Lefevre <vincent at vinc17.net> writes:

  So, if I understand correctly, this means that if the user chooses
  to set -m32 in CFLAGS, he might have to try different ABI values
  before finding one that works (because -m32 does not necessarily
  imply 32-bit limbs). This is not nice.

It is not easy to find anything better than what we have today.

The current strategy was chosen to work best for most users, and work
best here means to give optimal GMP performance.  If the optimal "ABI"
does not work, the next best "ABI" is tried, and so on.

The optimal "ABI" can easily be 5 times faster then the 2nd best "ABI".

Clearly this has some drawbacks.  E.g., some 64-bit systems default to
generating 32-bit code, and this code might not link to the newly built
GMP.  

It is less common that people set CC/CFLAGS to bad values (or at least
we don't hear about that very often).  I don't think we should try to
accomodate that since it would result in lots of fragile complexity.
(If you don't agree, please see the logic for "ABI" -> (CFLAGS,mpn_path)
selection.)

-- 
Torbjörn
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