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bug#32463: 27.0.50; (logior -1) => 4611686018427387903

From: Andy Moreton
Subject: bug#32463: 27.0.50; (logior -1) => 4611686018427387903
Date: Sun, 19 Aug 2018 11:34:55 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1.50 (windows-nt)

On Sat 18 Aug 2018, Paul Eggert wrote:

> My bigger concern is memory management, along with integer overflow in size or
> bitcount calculation. Copies are made of bignums when not needed, behavior is
> dicey if memory is exhausted during bignum computation, and I'm afraid C-g
> will have problems when bignums get large. I don't have a good handle on this
> stuff yet. I have put in some sanity checks (e.g., see check_bignum_size in
> emacs.c) but I suspect more are needed. In particular, Fexpt will need to be
> careful as it is a good way to explode a bignum's size.

Indeed. There are many places that create a temporary bignum, and thus
call mpz_init/mpz_clear frequently. I haven't profiled this, but it may
be an opportunuty for some optimization.

Fixing C-g will require awkward changes to either GMP and/or emacs.


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