Make the code base clean under -Wwrite-strings.

I've also added that warning option and -Werror to the build script,
so that I'll find out if I break this property in future.

1 files changed, 3 insertions, 3 deletions

diff --git a/singles.c b/singles.c
index c88c6c5..5929d82 100644
--- a/singles.c
+++ b/singles.c
@@ -330,10 +330,10 @@ static int c2n(char c) {
 }
 
 static void unpick_desc(const game_params *params, const char *desc,
-                        game_state **sout, char **mout)
+                        game_state **sout, const char **mout)
 {
     game_state *state = blank_game(params->w, params->h);
-    char *msg = NULL;
+    const char *msg = NULL;
     int num = 0, i = 0;
 
     if (strlen(desc) != state->n) {
@@ -1412,7 +1412,7 @@ randomise:
 
 static const char *validate_desc(const game_params *params, const char *desc)
 {
-    char *ret = NULL;
+    const char *ret = NULL;
 
     unpick_desc(params, desc, NULL, &ret);
     return ret;