diff --git a/database/DBtcontact.c b/database/DBtcontact.c
index 3a6b1fb0..9a6ef3eb 100644
--- a/database/DBtcontact.c
+++ b/database/DBtcontact.c
@@ -953,24 +953,22 @@ DBFullResidueMask(type, rmask)
     TileType type;
     TileTypeBitMask *rmask;
 {
-    TileType t;
-    TileTypeBitMask *lmask;
-    LayerInfo *li, *lr;
-
-    li = &dbLayerInfo[type];
-    lmask = &li->l_residues;
-    TTMaskZero(rmask);
+    LayerInfo *li = &dbLayerInfo[type];
+    const TileTypeBitMask *lmask = &li->l_residues;
 
     if (type < DBNumUserLayers)
     {
-	TTMaskSetMask(rmask, &li->l_residues);
+	TTMaskCopy(rmask, lmask);
     }
     else
     {
-	for (t = TT_TECHDEPBASE; t < DBNumUserLayers; t++)
+	TileType t;
+	const int tt_last = DBNumUserLayers;
+	TTMaskZero(rmask);
+	for (t = TT_TECHDEPBASE; t < tt_last; t++)
 	    if (TTMaskHasType(lmask, t))
 	    {
-		lr = &dbLayerInfo[t];
+		LayerInfo *lr = &dbLayerInfo[t];
 		TTMaskSetMask(rmask, &lr->l_residues);
 	    }
     }
diff --git a/database/database.h.in b/database/database.h.in
index 6801a7cd..eaa9ff97 100644
--- a/database/database.h.in
+++ b/database/database.h.in
@@ -877,7 +877,7 @@ extern TileType DBTechFindStacking();
 extern bool DBIsContact();
 extern PlaneMask DBLayerPlanes();
 
-extern TileTypeBitMask *DBResidueMask();
+extern __nodiscard__ TileTypeBitMask *DBResidueMask(TileType type);
 extern void DBFullResidueMask();
 
     /* Miscellaneous */
diff --git a/scripts/makedbh.in b/scripts/makedbh.in
index 83ccaaef..64eb6738 100755
--- a/scripts/makedbh.in
+++ b/scripts/makedbh.in
@@ -51,6 +51,10 @@ add_generated_mask_macro(
     "TTMaskZero(m)",
     "(m)->tt_words[{i}] = 0",
 )
+add_generated_mask_macro(
+    "TTMaskCopy(m, n)",
+    "(m)->tt_words[{i}] = (n)->tt_words[{i}]",
+)
 add_generated_mask_macro(
     "TTMaskIsZero(m)",
     "(m)->tt_words[{i}] == 0",
diff --git a/utils/magic.h b/utils/magic.h
index ded4bf1c..25043c46 100644
--- a/utils/magic.h
+++ b/utils/magic.h
@@ -194,6 +194,21 @@ extern char AbortMessage[];
  /* looking to squash excessive -Wpedantic warnings ? add into defs.mak: CPPFLAGS += -Wno-variadic-macros */
  #define ANALYSER_NONNULL(n...) __attribute__((nonnull(n)))
  #define ANALYSER_RETURNS_NONNULL __attribute__((returns_nonnull))
+
+ /* These have keyword like behaviour so __nodiscard__ looks more like a keyword and is recognisable as such
+  * the historic use of __inline__ set a precedent on how backward compatibiliy maybe achieved for such things
+  */
+
+#if (defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 202311L))
+ /* since C23 but maybe some compilers supported it before their official C23 releases */
+ #define __nodiscard__ [[nodiscard]]
+#elif (defined(__GNUC__) && (__GNUC__ >= 4))
+ #define __nodiscard__ __attribute__((warn_unused_result))
+#elif (defined(__clang__) && (__clang_major__ >= 1))
+ #define __nodiscard__ __attribute__((warn_unused_result))
+#else
+ #define __nodiscard__ /* */
+#endif
 #else
  #define ATTR_FORMAT_PRINTF_1 /* */
  #define ATTR_FORMAT_PRINTF_2 /* */
@@ -207,6 +222,8 @@ extern char AbortMessage[];
  #define ANALYSER_MALLOC(dealloc, idx) /* */
  #define ANALYSER_NONNULL(n...) /* */
  #define ANALYSER_RETURNS_NONNULL /* */
+
+ #define __nodiscard__ /* */
 #endif
 
 /* ---------------- Start of Machine Configuration Section ----------------- */