diff --git a/tools/qfcc/include/def.h b/tools/qfcc/include/def.h
index 09033fa03..290510fa0 100644
--- a/tools/qfcc/include/def.h
+++ b/tools/qfcc/include/def.h
@@ -93,16 +93,23 @@ typedef struct def_s {
 	struct daglabel_s *daglabel;///< daglabel for this def
 	struct flowvar_s *flowvar;	///< flowvar for this def
 
-	unsigned    offset_reloc:1;	///< use *_def_ofs relocs
-	unsigned    initialized:1;	///< the def has been initialized
-	unsigned    constant:1;		///< stores constant value
-	unsigned    global:1;		///< globally declared def
-	unsigned    external:1;		///< externally declared def
-	unsigned    local:1;		///< function local def
-	unsigned    param:1;		///< function param def
-	unsigned    argument:1;		///< function argument def
-	unsigned    system:1;		///< system def
-	unsigned    nosave:1;		///< don't set DEF_SAVEGLOBAL
+	union {
+		struct {
+	        bool    offset_reloc:1;	///< use *_def_ofs relocs
+	        bool    initialized:1;	///< the def has been initialized
+	        bool    constant:1;		///< stores constant value
+	        bool    readonly:1;
+	        bool    writeonly:1;
+	        bool    global:1;		///< globally declared def
+	        bool    external:1;		///< externally declared def
+	        bool    local:1;		///< function local def
+	        bool    param:1;		///< function param def
+	        bool    argument:1;		///< function argument def
+	        bool    system:1;		///< system def
+	        bool    nosave:1;		///< don't set DEF_SAVEGLOBAL
+		};
+		unsigned    storage_bits;
+	};
 
 	rua_loc_t   loc;			///< declaring/defining source location
 
diff --git a/tools/qfcc/source/def.c b/tools/qfcc/source/def.c
index 48b621a06..27fb6d9a2 100644
--- a/tools/qfcc/source/def.c
+++ b/tools/qfcc/source/def.c
@@ -68,72 +68,42 @@ ALLOC_STATE (def_t, defs);
 static void
 set_storage_bits (def_t *def, storage_class_t storage)
 {
+	def->storage_bits = 0;
 	switch (storage) {
 		case sc_out:
 		case sc_buffer:
 		case sc_shared:
-			def->global = 1;
-			def->external = 0;
-			def->local = 0;
-			def->param = 0;
-			def->argument = 0;
+			def->global = true;
 			break;
 		case sc_system:
-			def->system = 1;
+			def->system = true;
 			// fall through
 		case sc_global:
-			def->global = 1;
-			def->external = 0;
-			def->local = 0;
-			def->param = 0;
-			def->argument = 0;
+			def->global = true;
 			break;
 		case sc_in:
 		case sc_uniform:
-			def->global = 1;
-			def->constant = 1;
-			def->external = 0;
-			def->local = 0;
-			def->param = 0;
-			def->argument = 0;
+			def->global = true;
+			def->readonly = true;
 			break;
 		case sc_extern:
-			def->global = 1;
-			def->external = 1;
-			def->local = 0;
-			def->param = 0;
-			def->argument = 0;
+			def->global = true;
+			def->external = true;
 			break;
 		case sc_static:
-			def->external = 0;
-			def->global = 0;
-			def->local = 0;
-			def->param = 0;
-			def->argument = 0;
 			break;
 		case sc_local:
-			def->external = 0;
-			def->global = 0;
-			def->local = 1;
-			def->param = 0;
-			def->argument = 0;
+			def->local = true;
 			break;
 		case sc_param:
-			def->external = 0;
-			def->global = 0;
-			def->local = 1;
-			def->param = 1;
-			def->argument = 0;
+			def->local = true;
+			def->param = true;
 			break;
 		case sc_argument:
-			def->external = 0;
-			def->global = 0;
-			def->local = 1;
-			def->param = 0;
-			def->argument = 1;
+			def->local = true;
+			def->argument = true;
 			break;
 	}
-	def->initialized = 0;
 }
 
 def_t *
@@ -144,12 +114,12 @@ new_def (const char *name, const type_t *type, defspace_t *space,
 
 	ALLOC (16384, def_t, defs, def);
 
-	def->return_addr = __builtin_return_address (0);
-
-	def->name = name ? save_string (name) : 0;
-	def->type = type;
-
-	def->loc = pr.loc;
+	*def = (def_t) {
+		.type = type,
+		.name = name ? save_string (name) : 0,
+		.loc = pr.loc,
+		.return_addr = __builtin_return_address (0),
+	};
 
 	set_storage_bits (def, storage);