diff --git a/devel.but b/devel.but
index c201a3e..fd16151 100644
--- a/devel.but
+++ b/devel.but
@@ -5337,6 +5337,16 @@ equivalent to a bitwise-AND with \cw{~MOD_MASK}.
 Swap two regions of memory of \cw{size} bytes. The two regions must
 not overlap.
 
+\S{utils-compare-integers} \cw{compare_integers()}
+
+\c int compare_integers(const void *av, const void *bv);
+
+Compare the ints pointed to by \c{av} and \c{bv}. It returns an
+integer less than, equal to, or greater than zero if the first
+argument is respectively less than, equal to, or greater than the
+second. This function is intended to be passed to \c{qsort()} for
+sorting ints in ascending order.
+
 \C{writing} How to write a new puzzle
 
 This chapter gives a guide to how to actually write a new puzzle:
diff --git a/inertia.c b/inertia.c
index d120411..fe174f3 100644
--- a/inertia.c
+++ b/inertia.c
@@ -722,18 +722,6 @@ static int move_goes_to(int w, int h, char *grid, int x, int y, int d)
     return (y*w+x)*DP1+dr;
 }
 
-static int compare_integers(const void *av, const void *bv)
-{
-    const int *a = (const int *)av;
-    const int *b = (const int *)bv;
-    if (*a < *b)
-	return -1;
-    else if (*a > *b)
-	return +1;
-    else
-	return 0;
-}
-
 static char *solve_game(const game_state *state, const game_state *currstate,
                         const char *aux, const char **error)
 {
diff --git a/misc.c b/misc.c
index f9eaf5d..8e96d67 100644
--- a/misc.c
+++ b/misc.c
@@ -351,6 +351,17 @@ void draw_rect_corners(drawing *dr, int cx, int cy, int r, int col)
     draw_line(dr, cx + r, cy + r, cx + r/2, cy + r, col);
 }
 
+int compare_integers(const void *av, const void *bv) {
+    const int *a = (const int *)av;
+    const int *b = (const int *)bv;
+    if (*a < *b)
+	return -1;
+    else if (*a > *b)
+	return +1;
+    else
+	return 0;
+}
+
 char *move_cursor(int button, int *x, int *y, int maxw, int maxh, bool wrap,
     bool *visible)
 {
diff --git a/puzzles.h b/puzzles.h
index 2c52bc6..f1022ea 100644
--- a/puzzles.h
+++ b/puzzles.h
@@ -454,6 +454,9 @@ char *button2label(int button);
  * standard per clause 7.26.11.1.) */
 void swap_regions(void *av, void *bv, size_t size);
 
+/* comparator for sorting ints with qsort() */
+int compare_integers(const void *av, const void *bv);
+
 /*
  * dsf.c
  */
diff --git a/twiddle.c b/twiddle.c
index b3aa06f..49d8db7 100644
--- a/twiddle.c
+++ b/twiddle.c
@@ -532,18 +532,6 @@ static void free_game(game_state *state)
     sfree(state);
 }
 
-static int compare_int(const void *av, const void *bv)
-{
-    const int *a = (const int *)av;
-    const int *b = (const int *)bv;
-    if (*a < *b)
-	return -1;
-    else if (*a > *b)
-	return +1;
-    else
-	return 0;
-}
-
 static char *solve_game(const game_state *state, const game_state *currstate,
                         const char *aux, const char **error)
 {
@@ -758,7 +746,7 @@ static game_state *execute_move(const game_state *from, const char *move)
 	 * conveniently being able to get hold of a clean state from
 	 * which to practise manoeuvres.
 	 */
-	qsort(ret->grid, ret->w*ret->h, sizeof(int), compare_int);
+	qsort(ret->grid, ret->w*ret->h, sizeof(int), compare_integers);
 	for (i = 0; i < ret->w*ret->h; i++)
 	    ret->grid[i] &= ~3;
 	ret->used_solve = true;