simon-git: puzzles (master): Simon Tatham

[Commits to Tartarus hosted VCS]

TL;DR:
  664deae Fix two bugs in Range's solver_reasoning_recursion().

Repository:     https://git.tartarus.org/simon/puzzles.git
On the web:     https://git.tartarus.org/?p=simon/puzzles.git
Branch updated: master
Committer:      Simon Tatham <anakin at pobox.com>
Date:           2018-04-13 19:20:44

commit 664deaea597307bb5b055897384ae06a63424183
web diff https://git.tartarus.org/?p=simon/puzzles.git;a=commitdiff;h=664deaea597307bb5b055897384ae06a63424183;hp=d95f476d8b61dcbb9dc1c9bc9398cb295096cd2c
Author: Stephen Clavering <stephen at clavering.me.uk>
Date:   Thu Apr 12 21:15:17 2018 +0100

    Fix two bugs in Range's solver_reasoning_recursion().
    
    Firstly, it tries to use newstate after freeing it.  I haven't come up
    with any way of actually triggering that bug.  I suppose you'd need a
    grid that required recursion to solve, which the generator of course
    does not normally create.
    
    Secondly, it stores M_BLACK or M_WHITE in the grid before doing the
    recursion, whereas it should store BLACK or WHITE.  I believe that since
    it tries M_BLACK first, which is zero, and since it's trying it on an
    undecided square (also zero), this leads to infinite recursion, and an
    eventual crash once you run out of stack space.
    
    You can (sometimes) trigger this by asking for a hint on a grid where
    you've already made a mistake.
    
    e.g. on the puzzle desc below there's a "9" at (13,7).  If you place a
    black tile to its immediate left and right - (12,7) and (14,7) - then
    press 'h', you get a beachball and then crash (on macOS at least - I
    presume other OSes are similar).
    
    15x15:i5g4d16a7a7c3b3b11f11_15d3p8b7_8b4h18c4d13b4i7a16k9a9i4b2d10c14h11b10_10b17p6d8_7f9b8b11c10a2a5d5g7i

 range.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)