Lazy mpz allocation

[Torbjörn Granlund]

"Marco Bodrato" <bodrato at mail.dm.unipi.it> writes:

  I looked into the code and realised that my proposal requires an
  MPZ_REALLOC or if(ALLOC(x)==0) branch in ANY place where we write into an
  mpz_t. E.g. mpz_combit starts with:
  
    if (limb_index + 1 < SIZ(x)) {
      PTR(x)[limb_index] ^= bit;
      return;
    }
  
  If we allow the ALLOC(x)==0 && SIZ(x) != 0 case, we need to insert a check
  also in the simpler cases...
  
I assume this argues against being lazy with SIZE(x), not against being
lazy with allocation?

Some weeks ago, I made a naive testsuite-driven attempt at implementing
lazy allocation.  I had 55 FAILures and 114 PASSes after having fixed
these files:

M mpz/clear.c
M mpz/clears.c
M mpz/init.c
M mpz/mul.c
M mpz/realloc.c
M mpz/realloc2.c
M mpz/set_si.c
M mpz/set_ui.c
M tests/mpz/t-limbs.c

Curiously, there are some tests/mpn failures too.

-- 
Torbjörn
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