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, 2 insertions, 2 deletions

diff --git a/grid.h b/grid.h
index fb8ac48..19079a4 100644
--- a/grid.h
+++ b/grid.h
@@ -116,8 +116,8 @@ typedef enum grid_type { GRIDGEN_LIST(ENUM) GRID_TYPE_MAX } grid_type;
 /* Free directly after use if non-NULL. Will never contain an underscore
  * (so clients can safely use that as a separator). */
 char *grid_new_desc(grid_type type, int width, int height, random_state *rs);
-char *grid_validate_desc(grid_type type, int width, int height,
-                         const char *desc);
+const char *grid_validate_desc(grid_type type, int width, int height,
+                               const char *desc);
 
 grid *grid_new(grid_type type, int width, int height, const char *desc);