progs/demos: Silence warn_unused_result warnings.
diff --git a/progs/demos/isosurf.c b/progs/demos/isosurf.c
index 2e9dff1..dd56965 100644
--- a/progs/demos/isosurf.c
+++ b/progs/demos/isosurf.c
@@ -132,9 +132,11 @@
 
    numverts = 0;
    while (!feof(f) && numverts<maxverts) {
-      fscanf( f, "%f %f %f  %f %f %f",
-	      &data[numverts][0], &data[numverts][1], &data[numverts][2],
-	      &data[numverts][3], &data[numverts][4], &data[numverts][5] );
+      int result;
+      result = fscanf( f, "%f %f %f  %f %f %f",
+	               &data[numverts][0], &data[numverts][1], &data[numverts][2],
+	               &data[numverts][3], &data[numverts][4], &data[numverts][5] );
+      (void) result;
       numverts++;
    }
    numverts--;