Some fixes for clang

src/ifcparse/Ifc2x3-schema.cpp

@@ -1791,6 +1791,7 @@ class IFC2X3_instance_factory : public IfcParse::instance_factory {
 
 
 #if defined(__clang__)
+__attribute__((optnone))
 #elif defined(__GNUC__) || defined(__GNUG__)
 #pragma GCC push_options
 #pragma GCC optimize ("O0")

src/ifcparse/Ifc4-schema.cpp

@@ -2105,6 +2105,7 @@ class IFC4_instance_factory : public IfcParse::instance_factory {
 
 
 #if defined(__clang__)
+__attribute__((optnone))
 #elif defined(__GNUC__) || defined(__GNUG__)
 #pragma GCC push_options
 #pragma GCC optimize ("O0")

src/ifcparse/IfcBaseClass.h

@@ -38,6 +38,10 @@ namespace IfcUtil {
 	class IFC_PARSE_API IfcBaseClass {
     protected:
 		IfcEntityInstanceData* data_;
+
+		static bool is_null(const IfcBaseClass* not_this) {
+			return !not_this;
+		}
         
 	public:
         IfcBaseClass() : data_(0) {}
@@ -52,7 +56,8 @@ namespace IfcUtil {
 
 		template <class T>
 		T* as() {
-			if (this == 0) {
+			// @todo: do not allow this to be null in the first place
+			if (is_null(this)) {
 				return static_cast<T*>(0);
 			}
 			return declaration().is(T::Class())
@@ -62,7 +67,7 @@ namespace IfcUtil {
 
 		template <class T>
 		const T* as() const {
-			if (this == 0) {
+			if (is_null(this)) {
 				return static_cast<const T*>(0);
 			}
 			return declaration().is(T::Class())

src/ifcparse/parse_ifcxml.cpp

@@ -527,7 +527,7 @@ static void start_element(void* user, const xmlChar* tag, const xmlChar** attrs)
 								instance_to_attribute(inst_or_reference, attr, newinst);
 								state->stack.back().inst()->data().setArgument(idx, attr);
 								state->stack.push_back(stack_node::instance(id_in_file, newinst));
-							} else if (auto select = attribute_type->as_named_type()->declared_type()->as_select_type()) {
+							} else if (attribute_type->as_named_type()->declared_type()->as_select_type()) {
 								// Select types cause an additional indirection, so the current stack node is simply repeated
 								state->stack.push_back(stack_node::select(state->stack.back().inst(), idx));
 							}