Fix warnings on release builds (not DEBUG_ENABLED)

Fixes the following Clang 5 warnings:
```
modules/bmp/image_loader_bmp.cpp:46:60: warning: comparison of unsigned expression < 0 is always false [-Wtautological-compare]
modules/bmp/image_loader_bmp.cpp:48:61: warning: comparison of unsigned expression < 0 is always false [-Wtautological-compare]
drivers/png/image_loader_png.cpp:231:20: warning: comparison of unsigned expression >= 0 is always true [-Wtautological-compare]
scene/gui/graph_edit.cpp:1045:8: warning: comparison of constant 0 with expression of type 'bool' is always false [-Wtautological-constant-out-of-range-compare]

core/class_db.cpp:812:13: warning: unused variable 'check' [-Wunused-variable]
core/io/file_access_pack.cpp:172:11: warning: unused variable 'ver_rev' [-Wunused-variable]
core/math/bsp_tree.cpp:195:13: warning: unused variable 'plane' [-Wunused-variable]
core/math/bsp_tree.cpp:168:6: warning: unused variable 'plane_count' [-Wunused-variable]
modules/gdscript/gdscript_function.cpp:685:10: warning: unused variable 'ok' [-Wunused-variable]
modules/gdscript/gdscript_function.cpp:706:10: warning: unused variable 'ok' [-Wunused-variable]
modules/gdscript/gdscript_function.cpp:755:19: warning: unused variable 'var_type' [-Wunused-variable]
modules/gdscript/gdscript_function.cpp:1306:12: warning: unused variable 'err' [-Wunused-variable]

modules/gdscript/gdscript_function.cpp:158:15: warning: unused function '_get_var_type' [-Wunused-function]
modules/gdscript/gdscript_parser.cpp:750:20: warning: unused variable 'lv' [-Wunused-variable]
modules/gdscript/gdscript_parser.cpp:59:15: warning: unused function '_find_function_name' [-Wunused-function]
scene/main/node.cpp:2489:13: warning: unused function '_Node_debug_sn' [-Wunused-function]
```

9 files changed, 27 insertions, 33 deletions

diff --git a/core/class_db.cpp b/core/class_db.cpp
index dcc07f8f41..71809d5454 100644
--- a/core/class_db.cpp
+++ b/core/class_db.cpp
@@ -809,10 +809,10 @@ void ClassDB::add_signal(StringName p_class, const MethodInfo &p_signal) {
 	ClassInfo *type = classes.getptr(p_class);
 	ERR_FAIL_COND(!type);
 
-	ClassInfo *check = type;
 	StringName sname = p_signal.name;
-#ifdef DEBUG_METHODS_ENABLED
 
+#ifdef DEBUG_METHODS_ENABLED
+	ClassInfo *check = type;
 	while (check) {
 		if (check->signal_map.has(sname)) {
 			ERR_EXPLAIN("Type " + String(p_class) + " already has signal: " + String(sname));
diff --git a/core/io/file_access_pack.cpp b/core/io/file_access_pack.cpp
index e3c8fb9eb8..40f756ba9a 100644
--- a/core/io/file_access_pack.cpp
+++ b/core/io/file_access_pack.cpp
@@ -169,11 +169,11 @@ bool PackedSourcePCK::try_open_pack(const String &p_path) {
 	uint32_t version = f->get_32();
 	uint32_t ver_major = f->get_32();
 	uint32_t ver_minor = f->get_32();
-	uint32_t ver_rev = f->get_32();
+	f->get_32(); // ver_rev
 
 	ERR_EXPLAIN("Pack version unsupported: " + itos(version));
 	ERR_FAIL_COND_V(version != PACK_VERSION, false);
-	ERR_EXPLAIN("Pack created with a newer version of the engine: " + itos(ver_major) + "." + itos(ver_minor) + "." + itos(ver_rev));
+	ERR_EXPLAIN("Pack created with a newer version of the engine: " + itos(ver_major) + "." + itos(ver_minor));
 	ERR_FAIL_COND_V(ver_major > VERSION_MAJOR || (ver_major == VERSION_MAJOR && ver_minor > VERSION_MINOR), false);
 
 	for (int i = 0; i < 16; i++) {
diff --git a/core/math/bsp_tree.cpp b/core/math/bsp_tree.cpp
index 6e51c56357..6ffc963783 100644
--- a/core/math/bsp_tree.cpp
+++ b/core/math/bsp_tree.cpp
@@ -165,7 +165,6 @@ int BSP_Tree::get_points_inside(const Vector3 *p_points, int p_point_count) cons
 	int pass_count = 0;
 	const Node *nodesptr = &nodes[0];
 	const Plane *planesptr = &planes[0];
-	int plane_count = planes.size();
 	int node_count = nodes.size();
 
 	if (node_count == 0) // no nodes!
@@ -192,9 +191,9 @@ int BSP_Tree::get_points_inside(const Vector3 *p_points, int p_point_count) cons
 				break;
 			}
 
-			uint16_t plane = nodesptr[idx].plane;
 #ifdef DEBUG_ENABLED
-
+			int plane_count = planes.size();
+			uint16_t plane = nodesptr[idx].plane;
 			ERR_FAIL_INDEX_V(plane, plane_count, false);
 #endif
 
diff --git a/drivers/png/image_loader_png.cpp b/drivers/png/image_loader_png.cpp
index 04acb9387e..a4ea889d3b 100644
--- a/drivers/png/image_loader_png.cpp
+++ b/drivers/png/image_loader_png.cpp
@@ -227,10 +227,7 @@ static void user_read_data(png_structp png_ptr, png_bytep data, png_size_t p_len
 	PNGReadStatus *rstatus;
 	rstatus = (PNGReadStatus *)png_get_io_ptr(png_ptr);
 
-	png_size_t to_read = p_length;
-	if (rstatus->size >= 0) {
-		to_read = MIN(p_length, rstatus->size - rstatus->offset);
-	}
+	png_size_t to_read = MIN(p_length, rstatus->size - rstatus->offset);
 	memcpy(data, &rstatus->image[rstatus->offset], to_read);
 	rstatus->offset += to_read;
 
diff --git a/modules/bmp/image_loader_bmp.cpp b/modules/bmp/image_loader_bmp.cpp
index 919731b52b..063508a25f 100644
--- a/modules/bmp/image_loader_bmp.cpp
+++ b/modules/bmp/image_loader_bmp.cpp
@@ -42,12 +42,9 @@ Error ImageLoaderBMP::convert_to_image(Ref<Image> p_image,
 
 	if (err == OK) {
 		size_t index = 0;
-		size_t width =
-				static_cast<size_t>(p_header.bmp_info_header.bmp_width < 0 ? -p_header.bmp_info_header.bmp_width : p_header.bmp_info_header.bmp_width);
-		size_t height =
-				static_cast<size_t>(p_header.bmp_info_header.bmp_height < 0 ? -p_header.bmp_info_header.bmp_height : p_header.bmp_info_header.bmp_height);
-		size_t bits_per_pixel =
-				static_cast<size_t>(p_header.bmp_info_header.bmp_bit_count);
+		size_t width = (size_t)p_header.bmp_info_header.bmp_width;
+		size_t height = (size_t)p_header.bmp_info_header.bmp_height;
+		size_t bits_per_pixel = (size_t)p_header.bmp_info_header.bmp_bit_count;
 
 		if (p_header.bmp_info_header.bmp_compression != 0) {
 			err = FAILED;
diff --git a/modules/gdscript/gdscript_function.cpp b/modules/gdscript/gdscript_function.cpp
index b935861652..8088dcf17d 100644
--- a/modules/gdscript/gdscript_function.cpp
+++ b/modules/gdscript/gdscript_function.cpp
@@ -155,6 +155,7 @@ String GDScriptFunction::_get_call_error(const Variant::CallError &p_err, const
 	return err_text;
 }
 
+#ifdef DEBUG_ENABLED
 static String _get_var_type(const Variant *p_type) {
 
 	String basestr;
@@ -164,7 +165,6 @@ static String _get_var_type(const Variant *p_type) {
 		if (!bobj) {
 			basestr = "null instance";
 		} else {
-#ifdef DEBUG_ENABLED
 			if (ObjectDB::instance_validate(bobj)) {
 				if (bobj->get_script_instance())
 					basestr = bobj->get_class() + " (" + bobj->get_script_instance()->get_script()->get_path().get_file() + ")";
@@ -173,10 +173,6 @@ static String _get_var_type(const Variant *p_type) {
 			} else {
 				basestr = "previously freed instance";
 			}
-
-#else
-			basestr = "Object";
-#endif
 		}
 
 	} else {
@@ -185,6 +181,7 @@ static String _get_var_type(const Variant *p_type) {
 
 	return basestr;
 }
+#endif
 
 #if defined(__GNUC__)
 #define OPCODES_TABLE                         \
@@ -676,6 +673,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 			OPCODE(OPCODE_SET_MEMBER) {
 
 				CHECK_SPACE(3);
+#ifdef DEBUG_ENABLED
 				int indexname = _code_ptr[ip + 1];
 				GD_ERR_BREAK(indexname < 0 || indexname >= _global_names_count);
 				const StringName *index = &_global_names_ptr[indexname];
@@ -683,7 +681,6 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 
 				bool valid;
 				bool ok = ClassDB::set_property(p_instance->owner, *index, *src, &valid);
-#ifdef DEBUG_ENABLED
 				if (!ok) {
 					err_text = "Internal error setting property: " + String(*index);
 					OPCODE_BREAK;
@@ -699,13 +696,13 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 			OPCODE(OPCODE_GET_MEMBER) {
 
 				CHECK_SPACE(3);
+#ifdef DEBUG_ENABLED
 				int indexname = _code_ptr[ip + 1];
 				GD_ERR_BREAK(indexname < 0 || indexname >= _global_names_count);
 				const StringName *index = &_global_names_ptr[indexname];
 				GET_VARIANT_PTR(dst, 2);
-				bool ok = ClassDB::get_property(p_instance->owner, *index, *dst);
 
-#ifdef DEBUG_ENABLED
+				bool ok = ClassDB::get_property(p_instance->owner, *index, *dst);
 				if (!ok) {
 					err_text = "Internal error getting property: " + String(*index);
 					OPCODE_BREAK;
@@ -752,13 +749,13 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 			OPCODE(OPCODE_ASSIGN_TYPED_BUILTIN) {
 
 				CHECK_SPACE(4);
-				Variant::Type var_type = (Variant::Type)_code_ptr[ip + 1];
 				GET_VARIANT_PTR(dst, 2);
 				GET_VARIANT_PTR(src, 3);
 
+#ifdef DEBUG_ENABLED
+				Variant::Type var_type = (Variant::Type)_code_ptr[ip + 1];
 				GD_ERR_BREAK(var_type < 0 || var_type >= Variant::VARIANT_MAX);
 
-#ifdef DEBUG_ENABLED
 				if (src->get_type() != var_type) {
 					if (Variant::can_convert_strict(src->get_type(), var_type)) {
 						Variant::CallError ce;
@@ -1282,10 +1279,11 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 						OPCODE_BREAK;
 					}
 #endif
+
 					Object *obj = argobj->operator Object *();
 					String signal = argname->operator String();
-#ifdef DEBUG_ENABLED
 
+#ifdef DEBUG_ENABLED
 					if (!obj) {
 						err_text = "First argument of yield() is null.";
 						OPCODE_BREAK;
@@ -1302,13 +1300,13 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 						OPCODE_BREAK;
 					}
 
-#endif
 					Error err = obj->connect(signal, gdfs.ptr(), "_signal_callback", varray(gdfs), Object::CONNECT_ONESHOT);
-#ifdef DEBUG_ENABLED
 					if (err != OK) {
 						err_text = "Error connecting to signal: " + signal + " during yield().";
 						OPCODE_BREAK;
 					}
+#else
+					obj->connect(signal, gdfs.ptr(), "_signal_callback", varray(gdfs), Object::CONNECT_ONESHOT);
 #endif
 				}
 
diff --git a/modules/gdscript/gdscript_parser.cpp b/modules/gdscript/gdscript_parser.cpp
index 2fa5084d84..a79fcccaeb 100644
--- a/modules/gdscript/gdscript_parser.cpp
+++ b/modules/gdscript/gdscript_parser.cpp
@@ -56,7 +56,9 @@ T *GDScriptParser::alloc_node() {
 	return t;
 }
 
+#ifdef DEBUG_ENABLED
 static String _find_function_name(const GDScriptParser::OperatorNode *p_call);
+#endif // DEBUG_ENABLED
 
 bool GDScriptParser::_end_statement() {
 
@@ -747,7 +749,6 @@ GDScriptParser::Node *GDScriptParser::_parse_expression(Node *p_parent, bool p_s
 			while (!bfn && b) {
 				if (b->variables.has(identifier)) {
 					IdentifierNode *id = alloc_node<IdentifierNode>();
-					LocalVarNode *lv = b->variables[identifier];
 					id->name = identifier;
 					id->declared_block = b;
 					id->line = id_line;
@@ -755,6 +756,7 @@ GDScriptParser::Node *GDScriptParser::_parse_expression(Node *p_parent, bool p_s
 					bfn = true;
 
 #ifdef DEBUG_ENABLED
+					LocalVarNode *lv = b->variables[identifier];
 					switch (tokenizer->get_token()) {
 						case GDScriptTokenizer::TK_OP_ASSIGN_ADD:
 						case GDScriptTokenizer::TK_OP_ASSIGN_BIT_AND:
diff --git a/scene/gui/graph_edit.cpp b/scene/gui/graph_edit.cpp
index 0ffaac20f6..b4fd7484e9 100644
--- a/scene/gui/graph_edit.cpp
+++ b/scene/gui/graph_edit.cpp
@@ -1042,7 +1042,7 @@ void GraphEdit::set_connection_activity(const StringName &p_from, int p_from_por
 
 		if (E->get().from == p_from && E->get().from_port == p_from_port && E->get().to == p_to && E->get().to_port == p_to_port) {
 
-			if (ABS(E->get().activity != p_activity)) {
+			if (ABS(E->get().activity - p_activity) < CMP_EPSILON) {
 				//update only if changed
 				top_layer->update();
 				connections_layer->update();
diff --git a/scene/main/node.cpp b/scene/main/node.cpp
index d3282c6ada..8189e77861 100644
--- a/scene/main/node.cpp
+++ b/scene/main/node.cpp
@@ -2486,6 +2486,7 @@ void Node::_set_tree(SceneTree *p_tree) {
 		tree_changed_b->tree_changed();
 }
 
+#ifdef DEBUG_ENABLED
 static void _Node_debug_sn(Object *p_obj) {
 
 	Node *n = Object::cast_to<Node>(p_obj);
@@ -2507,6 +2508,7 @@ static void _Node_debug_sn(Object *p_obj) {
 		path = String(p->get_name()) + "/" + p->get_path_to(n);
 	print_line(itos(p_obj->get_instance_id()) + " - Stray Node: " + path + " (Type: " + n->get_class() + ")");
 }
+#endif // DEBUG_ENABLED
 
 void Node::_print_stray_nodes() {
 
@@ -2516,7 +2518,6 @@ void Node::_print_stray_nodes() {
 void Node::print_stray_nodes() {
 
 #ifdef DEBUG_ENABLED
-
 	ObjectDB::debug_objects(_Node_debug_sn);
 #endif
 }