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Re: Bignum speedup patch causes crash at startup

From: Eli Zaretskii
Subject: Re: Bignum speedup patch causes crash at startup
Date: Tue, 04 Sep 2018 18:10:30 +0300

> From: Andy Moreton <address@hidden>
> Date: Tue, 04 Sep 2018 15:21:11 +0100
> The recent changes in commit fe042e9d ("Speed up (+ 2 2) by a factor of
> 10") cause an immediate crash in 64bit emacs on Windows.

Based on the backtrace I see here, crystal ball says that the new
function init_bignum_once is the problem: it is called during dumping,
before the call to mp_set_memory_functions, which tells GMP to use our
memory-allocation functions.  So GMP uses the "normal" malloc/free to
allocate the data, and then Emacs crashes when it tries to realloc
that after dumping.

I wonder how this was supposed to work on other platforms, since you
cannot generally assume that memory allocated by a function from some
malloc family can be safely freed/reallocated using a function from
another family.  One must use the same family.

Paul, why do we need to call init_bignum_once at dump time?

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