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Galaxies: fix recursion depth limit in solver.

The static variable 'solver_recurse_depth' is _mostly_ used by the
standalone solver, to appropriately indent the solver diagnostics for
the current recursion level. So most uses of it are guarded by an
'#ifdef STANDALONE_SOLVER' statement, or some equivalent (such as
being inside the solvep() macro).

One exception is the check that limits the recursion depth to 5, to
avoid getting hung up forever on a too-hard game. Unfortunately, this
check depends on the variable actually incrementing when we recurse
another level - and it wasn't, because the increment itself was under
ifdef! So the generator in live Galaxies could recurse arbitrarily
deep, and generate puzzles that the standalone solver found too hard
_even_ at Unreasonable mode.

Removed the ifdefs, so that solver_recurse_depth is now incremented
and decremented. Also, make sure to initialise the depth to 0 at the
start of a solver run, just in case it had a bogus value left over
from a previous run.

--- a/galaxies.c

+++ b/galaxies.c

@@ -187,6 +187,7 @@

 };

 static bool check_complete(const game_state *state, int *dsf, int *colours);

+static int solver_state_inner(game_state *state, int maxdiff);

 static int solver_state(game_state *state, int maxdiff);

 static int solver_obvious(game_state *state);

 static int solver_obvious_dot(game_state *state, space *dot);

@@ -2415,9 +2416,7 @@

            solver_recurse_depth*4, "",

            rctx.best->x, rctx.best->y, rctx.bestn));

-#ifdef STANDALONE_SOLVER

     solver_recurse_depth++;

-#endif

     ingrid = snewn(gsz, space);

     memcpy(ingrid, state->grid, gsz * sizeof(space));

@@ -2432,7 +2431,7 @@

                          state->dots[n]->x, state->dots[n]->y,

                          "Attempting for recursion");

-        ret = solver_state(state, maxdiff);

+        ret = solver_state_inner(state, maxdiff);

         if (diff == DIFF_IMPOSSIBLE && ret != DIFF_IMPOSSIBLE) {

             /* we found our first solved grid; copy it away. */

@@ -2464,9 +2463,7 @@

             break;

     }

-#ifdef STANDALONE_SOLVER

     solver_recurse_depth--;

-#endif

     if (outgrid) {

         /* we found (at least one) soln; copy it back to state */

@@ -2477,7 +2474,7 @@

     return diff;

 }

-static int solver_state(game_state *state, int maxdiff)

+static int solver_state_inner(game_state *state, int maxdiff)

 {

     solver_ctx *sctx = new_solver(state);

     int ret, diff = DIFF_NORMAL;

@@ -2542,6 +2539,12 @@

 #endif

     return diff;

+}

+

+static int solver_state(game_state *state, int maxdiff)

+{

+    solver_recurse_depth = 0;

+    return solver_state_inner(state, maxdiff);

 }

 #ifndef EDITOR