- Silencing some gcc warnings (yay! I can finally use this setup

again)
- Graph Editor "Active Keyframe" panel now displays more descriptive
error messages. In particular, hopefully this helps to alert users of
the default generator modifier for Driver F-Curves
- The first F-Modifier added to a list is now set to be active one for
that list.

source/blender/blenkernel/intern/fmodifier.c

@@ -1009,6 +1009,10 @@ FModifier *add_fmodifier (ListBase *modifiers, int type)
 	fcm->flag = FMODIFIER_FLAG_EXPANDED;
 	BLI_addtail(modifiers, fcm);
 	
+	/* tag modifier as "active" if no other modifiers exist in the stack yet */
+	if (modifiers->first == modifiers->last)
+		fcm->flag |= FMODIFIER_FLAG_ACTIVE;
+	
 	/* add modifier's data */
 	fcm->data= MEM_callocN(fmi->size, fmi->structName);
 	

source/blender/blenkernel/intern/key.c

@@ -1191,7 +1191,7 @@ static void do_curve_key(Scene *scene, Object *ob, Key *key, char *out, int tot)
 
 	if(key->slurph  && key->type!=KEY_RELATIVE) {
 		Nurb *nu;
-		int mode, i= 0, remain= 0, estep, count;
+		int mode=0, i= 0, remain= 0, estep=0, count=0;
 
 		delta= (float)key->slurph / tot;
 

source/blender/editors/armature/editarmature.c

@@ -5037,7 +5037,7 @@ static int pose_clear_rot_exec(bContext *C, wmOperator *UNUSED(op))
 			else {
 				/* perform clamping using euler form (3-components) */
 				float eul[3], oldeul[3], quat1[4] = {0};
-				float qlen;
+				float qlen = 0.0f;
 				
 				if (pchan->rotmode == ROT_MODE_QUAT) {
 					qlen= normalize_qt_qt(quat1, pchan->quat);

source/blender/editors/space_graph/graph_buttons.c

@@ -278,8 +278,19 @@ static void graph_panel_key_properties(const bContext *C, Panel *pa)
 			if (bezt->ipo == BEZT_IPO_BEZ)
 				uiItemR(col, &bezt_ptr, "handle_right", 0, NULL, ICON_NULL);
 	}
-	else
-		uiItemL(layout, "No active keyframe on F-Curve", ICON_NULL);
+	else {
+		if ((fcu->bezt == NULL) && (fcu->modifiers.first)) {
+			/* modifiers only - so no keyframes to be active */
+			uiItemL(layout, "F-Curve only has F-Modifiers", ICON_NULL);
+			uiItemL(layout, "See Modifiers panel below", ICON_INFO);
+		}
+		else if (fcu->fpt) {
+			/* samples only */
+			uiItemL(layout, "F-Curve doesn't have any keyframes as it only contains sampled points", ICON_NULL);
+		}
+		else
+			uiItemL(layout, "No active keyframe on F-Curve", ICON_NULL);
+	}
 	
 	MEM_freeN(ale);
 }