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1. Adrian Cochrane (alcinnz@floss.social)'s status on Saturday, 11-Mar-2023 04:00:30 JST Adrian Cochrane

   Sometimes you want to avoid bugs caused by the finite number of bits a CPU-native number consists of. GNU provides a handful of libraries for dealing with this, & today I'll start studying GNU MultiPrecision (LibGMP).

   Amongst the main codebase (I'll go over the subsystems starting tomorrow), I see:

   * A handful of globals specifying memory-layout & version-numbers.
   * Lookuptables.
   * Utilities to get or set memory-allocation callbacks, offering reentrant or debugging values for them.

   1/?

   • Adrian Cochrane (alcinnz@floss.social)'s status on Saturday, 11-Mar-2023 04:17:25 JST Adrian Cochrane

     in reply to

     Furthermore, I see:

     * Raising SIGFPE exceptions.
     * Default allocator callbacks.
     * Scripts to generate lookuptables for division, factorials, jacobi symbol, fibonacci, etc.
     * Wrappers around the division routines.
     * Prime number testing (fastpath checks for 1, 3, 5, & 7 factors, otherwise uses slowpath loop for factors > 11).
     * Another handful of routines to raise SIGFPE signals.
     * Logarithms by testing against repeated bitshifts.
     * Couple variations of dividing 1 by a number ("inversion").

     2/?

   • theruran 🌐🏴 (theruran@hackers.town)'s status on Saturday, 11-Mar-2023 04:18:17 JST theruran 🌐🏴

     in reply to

     @alcinnz I have a good feeling that GMP is a good target for fuzzing.

   • Adrian Cochrane (alcinnz@floss.social)'s status on Saturday, 11-Mar-2023 04:18:17 JST Adrian Cochrane

     in reply to

     • theruran 🌐🏴

     @theruran Yeah, especially with the large amount of Assembly code it has!

   • Adrian Cochrane (alcinnz@floss.social)'s status on Saturday, 11-Mar-2023 04:31:29 JST Adrian Cochrane

     in reply to

     * Assertion support routines
     * Convert from doubles (takes a fair bit of code to decompose the double)
     * A C++ wrapper, to take advantage of operator overloading
     * Fraction comparator*s*
     * `2n%m` repeated p times
     * `n == 0 ? 0 : m-n`
     * Computing bitmasks to test for square-modulos of given number
     * Fairly sophisticated iterator over (small) prime numbers, for internal needs
     * Compute bitmask to detect prime numbers
     * Headerfiles, include macros & inline routines covering many operators

     3/3.1

   • Adrian Cochrane (alcinnz@floss.social)'s status on Saturday, 11-Mar-2023 04:38:15 JST Adrian Cochrane

     in reply to

     Some of those macros wraps Assembly code.

     4.1/4.1 Fin for today! Tomorrow: Mini-GMP & probably MPF!