From 59954d67f56b353ee560fa261071bf23141fb940 Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Sun, 22 Dec 2024 11:55:50 +0000
Subject: [PATCH] groupsolver: fix segfault accessing solver->names.

Reproduced via 'groupsolver -v 5i:l5_2b5h' (thanks to Arun Giridhar
for the report).

We had filled in subsolver.names, but then called
latin_solver_alloc(&subsolver), which nulled out that pointer again.

Solution: do those two things in the opposite order.
---
 latin.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/latin.c b/latin.c
index a2d5713..7e38083 100644
--- a/latin.c
+++ b/latin.c
@@ -819,17 +819,18 @@ static int latin_solver_recurse
 	    } else {
 		newctx = ctx;
 	    }
+	    if (latin_solver_alloc(&subsolver, outgrid, o)) {
 #ifdef STANDALONE_SOLVER
-	    subsolver.names = solver->names;
+                subsolver.names = solver->names;
 #endif
-	    if (latin_solver_alloc(&subsolver, outgrid, o))
                 ret = latin_solver_top(&subsolver, diff_recursive,
                                        diff_simple, diff_set_0, diff_set_1,
                                        diff_forcing, diff_recursive,
                                        usersolvers, valid, newctx,
                                        ctxnew, ctxfree);
-            else
+            } else {
                 ret = diff_impossible;
+            }
 	    latin_solver_free(&subsolver);
 	    if (ctxnew)
 		ctxfree(newctx);