diff --git a/src/ifcparse/IfcBaseClass.h b/src/ifcparse/IfcBaseClass.h
index 1a796db5bb..e79b0e71cc 100644
--- a/src/ifcparse/IfcBaseClass.h
+++ b/src/ifcparse/IfcBaseClass.h
@@ -37,7 +37,7 @@ namespace IfcUtil {
 class IFC_PARSE_API IfcBaseInterface {
   protected:
     static bool is_null(const IfcBaseInterface* not_this) {
-        return !not_this;
+        return not_this == nullptr;
     }
 
     template <typename T>
@@ -90,7 +90,7 @@ class IFC_PARSE_API IfcBaseClass : public virtual IfcBaseInterface {
     IfcEntityInstanceData* data_;
 
     static bool is_null(const IfcBaseClass* not_this) {
-        return !not_this;
+        return not_this == nullptr;
     }
 
   public:
diff --git a/src/ifcparse/IfcCharacterDecoder.cpp b/src/ifcparse/IfcCharacterDecoder.cpp
index bd0a101df9..c538e0f6db 100644
--- a/src/ifcparse/IfcCharacterDecoder.cpp
+++ b/src/ifcparse/IfcCharacterDecoder.cpp
@@ -135,16 +135,16 @@ class pure_impure_helper {
             if (EXPECTS_CHARACTER(parse_state)) {
                 builder_.push_back(IfcUtil::convert_codepage(codepage, current_char + 0x80));
                 parse_state = 0;
-            } else if (current_char == '\'' && !parse_state) {
+            } else if (current_char == '\'' && (parse_state == 0U)) {
                 parse_state = APOSTROPHE;
-            } else if (current_char == '\\' && !parse_state) {
+            } else if (current_char == '\\' && (parse_state == 0U)) {
                 parse_state = FIRST_SOLIDUS;
             } else if (current_char == '\\' && EXPECTS_SOLIDUS(parse_state)) {
-                if (parse_state & ALPHABET_DEFINITION ||
-                    parse_state & IGNORED_DIRECTIVE ||
-                    parse_state & ENDEXTENDED_0) {
+                if (((parse_state & ALPHABET_DEFINITION) != 0U) ||
+                    ((parse_state & IGNORED_DIRECTIVE) != 0U) ||
+                    ((parse_state & ENDEXTENDED_0) != 0U)) {
                     parse_state = hex = hex_count = 0;
-                } else if (parse_state & ENCOUNTERED_HEX) {
+                } else if ((parse_state & ENCOUNTERED_HEX) != 0U) {
                     parse_state += THIRD_SOLIDUS;
                     parse_state -= ENCOUNTERED_HEX;
                 } else {
@@ -173,8 +173,8 @@ class pure_impure_helper {
                 hex <<= 4;
                 parse_state += HEX((++hex_count));
                 hex += HEX_TO_INT(current_char);
-                if ((hex_count == 2 && !(parse_state & EXTENDED2)) ||
-                    (hex_count == 4 && !(parse_state & EXTENDED4)) ||
+                if ((hex_count == 2 && ((parse_state & EXTENDED2) == 0U)) ||
+                    (hex_count == 4 && ((parse_state & EXTENDED4) == 0U)) ||
                     (hex_count == 8)) {
                     builder_.push_back(hex);
                     if (hex_count == 2) {
@@ -185,9 +185,9 @@ class pure_impure_helper {
                     }
                     hex = hex_count = 0;
                 }
-            } else if (parse_state && !(
-                                          (current_char == '\\' && parse_state == FIRST_SOLIDUS) ||
-                                          (current_char == '\'' && parse_state == APOSTROPHE))) {
+            } else if ((parse_state != 0U) && !(
+                                                  (current_char == '\\' && parse_state == FIRST_SOLIDUS) ||
+                                                  (current_char == '\'' && parse_state == APOSTROPHE))) {
                 if (parse_state == APOSTROPHE && current_char != '\'') {
                     break;
                 }
@@ -255,16 +255,16 @@ void IfcCharacterDecoder::skip() {
     while ((current_char = file->Peek()) != 0) {
         if (EXPECTS_CHARACTER(parse_state)) {
             parse_state = 0;
-        } else if (current_char == '\'' && !parse_state) {
+        } else if (current_char == '\'' && (parse_state == 0U)) {
             parse_state = APOSTROPHE;
-        } else if (current_char == '\\' && !parse_state) {
+        } else if (current_char == '\\' && (parse_state == 0U)) {
             parse_state = FIRST_SOLIDUS;
         } else if (current_char == '\\' && EXPECTS_SOLIDUS(parse_state)) {
-            if (parse_state & ALPHABET_DEFINITION ||
-                parse_state & IGNORED_DIRECTIVE ||
-                parse_state & ENDEXTENDED_0) {
+            if (((parse_state & ALPHABET_DEFINITION) != 0U) ||
+                ((parse_state & IGNORED_DIRECTIVE) != 0U) ||
+                ((parse_state & ENDEXTENDED_0) != 0U)) {
                 parse_state = hex_count = 0;
-            } else if (parse_state & ENCOUNTERED_HEX) {
+            } else if ((parse_state & ENCOUNTERED_HEX) != 0U) {
                 parse_state += THIRD_SOLIDUS;
                 parse_state -= ENCOUNTERED_HEX;
             } else {
@@ -290,8 +290,8 @@ void IfcCharacterDecoder::skip() {
             parse_state += PAGE;
         } else if (IS_HEXADECIMAL(current_char) && EXPECTS_HEX(parse_state)) {
             parse_state += HEX((++hex_count));
-            if ((hex_count == 2 && !(parse_state & EXTENDED2)) ||
-                (hex_count == 4 && !(parse_state & EXTENDED4)) ||
+            if ((hex_count == 2 && ((parse_state & EXTENDED2) == 0U)) ||
+                (hex_count == 4 && ((parse_state & EXTENDED4) == 0U)) ||
                 (hex_count == 8)) {
                 if (hex_count == 2) {
                     parse_state = 0;
@@ -301,9 +301,9 @@ void IfcCharacterDecoder::skip() {
                 }
                 hex_count = 0;
             }
-        } else if (parse_state && !(
-                                      (current_char == '\\' && parse_state == FIRST_SOLIDUS) ||
-                                      (current_char == '\'' && parse_state == APOSTROPHE))) {
+        } else if ((parse_state != 0U) && !(
+                                              (current_char == '\\' && parse_state == FIRST_SOLIDUS) ||
+                                              (current_char == '\'' && parse_state == APOSTROPHE))) {
             if (parse_state == APOSTROPHE && current_char != '\'') {
                 break;
             }
diff --git a/src/ifcparse/IfcEntityInstanceData.h b/src/ifcparse/IfcEntityInstanceData.h
index 2b0543be64..d4786c7de3 100644
--- a/src/ifcparse/IfcEntityInstanceData.h
+++ b/src/ifcparse/IfcEntityInstanceData.h
@@ -84,7 +84,7 @@ class IFC_PARSE_API IfcEntityInstanceData {
         if (type_ == 0) {
             return 0;
         }
-        if (type_->as_entity()) {
+        if (type_->as_entity() != nullptr) {
             return type_->as_entity()->attribute_count();
         }
         return 1;
diff --git a/src/ifcparse/IfcGlobalId.cpp b/src/ifcparse/IfcGlobalId.cpp
index 8b613d6a7d..7b5d10b4a7 100644
--- a/src/ifcparse/IfcGlobalId.cpp
+++ b/src/ifcparse/IfcGlobalId.cpp
@@ -35,7 +35,7 @@ static const char* chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnop
 std::string base64(unsigned v, int l) {
     std::string r;
     r.reserve(l);
-    while (v) {
+    while (v != 0U) {
         r.push_back(chars[v % 64]);
         v /= 64;
     }
@@ -54,7 +54,7 @@ unsigned from_base64(const std::string& s) {
         for (std::string::const_iterator i = s.begin() + zeros; i != s.end(); ++i) {
             r *= 64;
             const char* c = strchr(chars, *i);
-            if (!c) {
+            if (c == nullptr) {
                 throw IfcParse::IfcException("Failed to decode GlobalId");
             }
             r += (unsigned)(c - chars);
diff --git a/src/ifcparse/IfcLogger.cpp b/src/ifcparse/IfcLogger.cpp
index 06f8dd07da..0711b8ca5d 100644
--- a/src/ifcparse/IfcLogger.cpp
+++ b/src/ifcparse/IfcLogger.cpp
@@ -126,7 +126,7 @@ void Logger::SetOutput(std::ostream* l1, std::ostream* l2) {
     wlog1 = wlog2 = 0;
     log1 = l1;
     log2 = l2;
-    if (!log2) {
+    if (log2 == nullptr) {
         log2 = &log_stream;
     }
 }
@@ -135,7 +135,7 @@ void Logger::SetOutput(std::wostream* l1, std::wostream* l2) {
     log1 = log2 = 0;
     wlog1 = l1;
     wlog2 = l2;
-    if (!wlog2) {
+    if (wlog2 == nullptr) {
         log2 = &log_stream;
     }
 }
@@ -160,17 +160,17 @@ void Logger::Message(Logger::Severity type, const std::string& message, const If
     if (type > max_severity) {
         max_severity = type;
     }
-    if ((log2 || wlog2) && type >= verbosity) {
+    if (((log2 != nullptr) || (wlog2 != nullptr)) && type >= verbosity) {
         if (format == FMT_PLAIN) {
-            if (log2) {
+            if (log2 != nullptr) {
                 plain_text_message(*log2, current_product, type, message, instance);
-            } else if (wlog2) {
+            } else if (wlog2 != nullptr) {
                 plain_text_message(*wlog2, current_product, type, message, instance);
             }
         } else if (format == FMT_JSON) {
-            if (log2) {
+            if (log2 != nullptr) {
                 json_message(*log2, current_product, type, message, instance);
-            } else if (wlog2) {
+            } else if (wlog2 != nullptr) {
                 json_message(*wlog2, current_product, type, message, instance);
             }
         }
@@ -192,9 +192,9 @@ void status(T& log1, const std::string& message, bool new_line) {
 }
 
 void Logger::Status(const std::string& message, bool new_line) {
-    if (log1) {
+    if (log1 != nullptr) {
         status(*log1, message, new_line);
-    } else if (wlog1) {
+    } else if (wlog1 != nullptr) {
         status(*wlog1, message, new_line);
     }
 }
diff --git a/src/ifcparse/IfcParse.cpp b/src/ifcparse/IfcParse.cpp
index 10109a6baf..0e1a92cf8f 100644
--- a/src/ifcparse/IfcParse.cpp
+++ b/src/ifcparse/IfcParse.cpp
@@ -210,7 +210,7 @@ void IfcSpfStream::Close() {
     }
 #endif
     delete[] buffer;
-    if (stream) {
+    if (stream != nullptr) {
         fclose(stream);
     }
 }
@@ -320,7 +320,7 @@ Token IfcSpfLexer::Next() {
         return NoneTokenPtr();
     }
 
-    while (skipWhitespace() || skipComment()) {
+    while ((skipWhitespace() != 0U) || (skipComment() != 0U)) {
     }
 
     if (stream->eof) {
@@ -342,7 +342,7 @@ Token IfcSpfLexer::Next() {
 
         // Read character and increment pointer if not starting a new token
         c = stream->Peek();
-        if (len && (c == '(' || c == ')' || c == '=' || c == ',' || c == ';' || c == '/')) {
+        if ((len != 0) && (c == '(' || c == ')' || c == '=' || c == ',' || c == ';' || c == '/')) {
             break;
         }
         stream->Inc();
@@ -353,7 +353,7 @@ Token IfcSpfLexer::Next() {
             decoder->skip();
         }
     }
-    if (len) {
+    if (len != 0) {
         return GeneralTokenPtr(this, pos, stream->Tell());
     }
     return NoneTokenPtr();
@@ -385,7 +385,7 @@ void IfcSpfLexer::TokenString(unsigned int offset, std::string& buffer) {
     buffer.clear();
     while (!stream->is_eof_at(offset)) {
         char c = stream->peek_at(offset);
-        if (buffer.size() && (c == '(' || c == ')' || c == '=' || c == ',' || c == ';' || c == '/')) {
+        if (!buffer.empty() && (c == '(' || c == ')' || c == '=' || c == ',' || c == ';' || c == '/')) {
             break;
         }
         stream->increment_at(offset);
@@ -639,7 +639,7 @@ boost::dynamic_bitset<> TokenFunc::asBinary(const Token& t) {
             if (i-- == 0) {
                 break;
             }
-            if (value & (1 << (3 - j))) {
+            if ((value & (1 << (3 - j))) != 0) {
                 bitset.set(i);
             }
         }
@@ -719,7 +719,7 @@ size_t IfcParse::IfcFile::load(unsigned entity_instance_name, const IfcParse::en
             // If num_attributes is zero we know this is a top-level entity instance (or header entity) being parsed.
             // There can only be parsed one of these at a time, so we can reuse the vector we have defined at the file
             // scope.
-            if (entity) {
+            if (entity != nullptr) {
                 vector = &internal_attribute_vector_;
             } else {
                 vector = &internal_attribute_vector_simple_type_;
@@ -733,7 +733,7 @@ size_t IfcParse::IfcFile::load(unsigned entity_instance_name, const IfcParse::en
 
     size_t return_value = 0;
 
-    while (next.startPos || next.lexer) {
+    while ((next.startPos != 0U) || (next.lexer != nullptr)) {
         if (TokenFunc::isOperator(next, ',')) {
             // do nothing
         } else if (TokenFunc::isOperator(next, ')')) {
@@ -768,9 +768,9 @@ size_t IfcParse::IfcFile::load(unsigned entity_instance_name, const IfcParse::en
         next = tokens->Next();
     }
 
-    if (vector) {
+    if (vector != nullptr) {
         // Obviously don't try and create a 0-length array.
-        if (num_attributes || vector->size()) {
+        if ((num_attributes != 0U) || !vector->empty()) {
             // @todo figure out whether all this logic is still necessary, since we know the
             // expected amount of attributes and shouldn't be able to access more than allowed
             // by the schema.
@@ -874,7 +874,7 @@ ArgumentList::operator aggregate_of_aggregate_of_instance::ptr() const {
             l->push(e);
         } else {
             auto token = dynamic_cast<const TokenArgument*>(arg);
-            int startpos = token ? token->token.startPos : 0;
+            int startpos = token != nullptr ? token->token.startPos : 0;
             std::string string_rep = this->toString();
             throw IfcInvalidTokenException(startpos, string_rep, "nested aggregate");
         }
@@ -1053,7 +1053,7 @@ void IfcParse::IfcFile::register_inverse(unsigned id_from, const IfcParse::entit
     // Assume a check on token type has already been performed
     auto e = from_entity;
     byref_excl[t.value_int].push_back(id_from);
-    while (e) {
+    while (e != nullptr) {
         byref[{t.value_int, e->index_in_schema(), attribute_index}].push_back(id_from);
         e = e->supertype();
     }
@@ -1062,7 +1062,7 @@ void IfcParse::IfcFile::register_inverse(unsigned id_from, const IfcParse::entit
 void IfcParse::IfcFile::register_inverse(unsigned id_from, const IfcParse::entity* from_entity, IfcUtil::IfcBaseClass* inst, int attribute_index) {
     auto e = from_entity;
     byref_excl[inst->data().id()].push_back(id_from);
-    while (e) {
+    while (e != nullptr) {
         byref[{inst->data().id(), e->index_in_schema(), attribute_index}].push_back(id_from);
         e = e->supertype();
     }
@@ -1070,7 +1070,7 @@ void IfcParse::IfcFile::register_inverse(unsigned id_from, const IfcParse::entit
 
 void IfcParse::IfcFile::unregister_inverse(unsigned id_from, const IfcParse::entity* from_entity, IfcUtil::IfcBaseClass* inst, int attribute_index) {
     auto e = from_entity;
-    while (e) {
+    while (e != nullptr) {
         std::vector<int>& ids = byref[{inst->data().id(), e->index_in_schema(), attribute_index}];
         std::vector<int>::iterator it = std::find(ids.begin(), ids.end(), id_from);
         if (it == ids.end()) {
@@ -1105,13 +1105,13 @@ std::string IfcEntityInstanceData::toString(bool upper) const {
     ss.imbue(std::locale::classic());
 
     std::string dt;
-    if (type_) {
+    if (type_ != nullptr) {
         dt = type()->name();
         if (upper) {
             boost::to_upper(dt);
         }
 
-        if (type()->as_entity() || id_ != 0) {
+        if ((type()->as_entity() != nullptr) || id_ != 0) {
             ss << "#" << id_ << "=";
         }
     }
@@ -1182,7 +1182,7 @@ void IfcEntityInstanceData::load() const {
     // type_ is 0 for header entities which have their size predetermined in code
     // in that we have attributes_ pre-constructed to the correct size in the constructor
     // in the other case load() will use a vector internally to grow to the size found in the file
-    size_t n = file->load(id(), type_ ? type_->as_entity() : nullptr, type_ ? tmp_data : attributes_, getArgumentCount());
+    size_t n = file->load(id(), type_ != nullptr ? type_->as_entity() : nullptr, type_ != nullptr ? tmp_data : attributes_, getArgumentCount());
     if (n != getArgumentCount()) {
         Logger::Error("Wrong number of attributes on instance with id #" + std::to_string(id_) +
                       " at offset " + std::to_string(this->offset_in_file()) +
@@ -1193,7 +1193,7 @@ void IfcEntityInstanceData::load() const {
     file->try_read_semicolon();
 
     // @todo does this need to be atomic somehow?
-    if (tmp_data) {
+    if (tmp_data != nullptr) {
         attributes_ = tmp_data;
     }
 }
@@ -1203,14 +1203,14 @@ namespace {
 // different handling of enumerations)
 IfcUtil::ArgumentType get_argument_type(const IfcParse::declaration* decl, size_t i) {
     const IfcParse::parameter_type* pt = 0;
-    if (decl->as_entity()) {
+    if (decl->as_entity() != nullptr) {
         pt = decl->as_entity()->attribute_by_index(i)->type_of_attribute();
         if (decl->as_entity()->derived()[i]) {
             return IfcUtil::Argument_DERIVED;
         }
-    } else if (decl->as_type_declaration() && i == 0) {
+    } else if ((decl->as_type_declaration() != nullptr) && i == 0) {
         pt = decl->as_type_declaration()->declared_type();
-    } else if (decl->as_enumeration_type() && i == 0) {
+    } else if ((decl->as_enumeration_type() != nullptr) && i == 0) {
         return IfcUtil::Argument_ENUMERATION;
     }
 
@@ -1416,7 +1416,7 @@ void IfcEntityInstanceData::setArgument(size_t i, Argument* a, IfcUtil::Argument
             // Remove leading and trailing '.'
             enum_literal = enum_literal.substr(1, enum_literal.size() - 2);
 
-            const IfcParse::enumeration_type* enum_type = type()->as_enumeration_type()
+            const IfcParse::enumeration_type* enum_type = type()->as_enumeration_type() != nullptr
                                                               ? type()->as_enumeration_type()
                                                               : type()->as_entity()->attribute_by_index(i)->type_of_attribute()->as_named_type()->declared_type()->as_enumeration_type();
 
@@ -1483,7 +1483,7 @@ void IfcEntityInstanceData::setArgument(size_t i, Argument* a, IfcUtil::Argument
             break;
         }
 
-        if (!copy) {
+        if (copy == nullptr) {
             return;
         }
 
@@ -1492,10 +1492,10 @@ void IfcEntityInstanceData::setArgument(size_t i, Argument* a, IfcUtil::Argument
 
     if (attributes_[i] != 0) {
         Argument* current_attribute = attributes_[i];
-        if (this->file) {
+        if (this->file != nullptr) {
 
             // Deregister old attribute guid in file guid map.
-            if (i == 0 && this->type() && this->file->ifcroot_type() && this->type()->is(*this->file->ifcroot_type())) {
+            if (i == 0 && (this->type() != nullptr) && (this->file->ifcroot_type() != nullptr) && this->type()->is(*this->file->ifcroot_type())) {
                 try {
                     auto guid = (std::string)*current_attribute;
                     auto it = this->file->internal_guid_map().find(guid);
@@ -1514,7 +1514,7 @@ void IfcEntityInstanceData::setArgument(size_t i, Argument* a, IfcUtil::Argument
         delete attributes_[i];
     }
 
-    if (this->file) {
+    if (this->file != nullptr) {
         // Register inverse indices in file
         register_inverse_visitor visitor(*this->file, *this);
         apply_individual_instance_visitor(new_attribute, i).apply(visitor);
@@ -1523,8 +1523,8 @@ void IfcEntityInstanceData::setArgument(size_t i, Argument* a, IfcUtil::Argument
     attributes_[i] = new_attribute;
 
     // Register new attribute guid in guid map
-    if (this->file) {
-        if (i == 0 && this->type() && this->file->ifcroot_type() && this->type()->is(*this->file->ifcroot_type())) {
+    if (this->file != nullptr) {
+        if (i == 0 && (this->type() != nullptr) && (this->file->ifcroot_type() != nullptr) && this->type()->is(*this->file->ifcroot_type())) {
             try {
                 auto guid = (std::string)*new_attribute;
                 auto it = this->file->internal_guid_map().find(guid);
@@ -1662,7 +1662,7 @@ void IfcFile::initialize_(IfcParse::IfcSpfStream* s) {
 
             /// @todo Printing to stdout in a library class feels weird. Maybe move the progress prints to the client code?
             // Update the status after every 1000 instances parsed
-            if (!((++progress) % 1000)) {
+            if (((++progress) % 1000) == 0) {
                 std::stringstream ss;
                 ss << "\r#" << current_id;
                 Logger::Status(ss.str(), false);
@@ -1708,7 +1708,7 @@ void IfcFile::initialize_(IfcParse::IfcSpfStream* s) {
                 }
                 insts->push(instance);
                 const IfcParse::declaration* pt = ty->as_entity()->supertype();
-                if (pt) {
+                if (pt != nullptr) {
                     ty = pt;
                 } else {
                     break;
@@ -1723,7 +1723,7 @@ void IfcFile::initialize_(IfcParse::IfcSpfStream* s) {
             byid[current_id] = instance;
 
             MaxId = (std::max)(MaxId, current_id);
-        } else if (token_stream[0].type == IfcParse::Token_IDENTIFIER && instance) {
+        } else if (token_stream[0].type == IfcParse::Token_IDENTIFIER && (instance != nullptr)) {
             register_inverse(current_id, instance->declaration().as_entity(), token_stream[0], attribute_index);
         } else if (token_stream[0].type == IfcParse::Token_OPERATOR && token_stream[0].value_char == '(') {
             paren_stack_depth++;
@@ -1913,7 +1913,7 @@ IfcUtil::IfcBaseClass* IfcFile::addEntity(IfcUtil::IfcBaseClass* entity, int id)
     // See whether the instance is already part of a file
     if (entity->data().file != 0) {
         if (entity->data().file == this) {
-            if (!entity->declaration().as_entity()) {
+            if (entity->declaration().as_entity() == nullptr) {
                 // While not a mapping that can be queried, we do need to free the instance later on
                 byidentity[new_entity->identity()] = new_entity;
             }
@@ -1939,13 +1939,13 @@ IfcUtil::IfcBaseClass* IfcFile::addEntity(IfcUtil::IfcBaseClass* entity, int id)
             IfcUtil::ArgumentType attr_type = attr->type();
 
             IfcParse::declaration* decl = 0;
-            if (entity->declaration().as_entity()) {
+            if (entity->declaration().as_entity() != nullptr) {
                 decl = 0;
                 const parameter_type* pt = entity->declaration().as_entity()->attribute_by_index(i)->type_of_attribute();
-                while (pt->as_aggregation_type()) {
+                while (pt->as_aggregation_type() != nullptr) {
                     pt = pt->as_aggregation_type()->type_of_element();
                 }
-                if (pt->as_named_type()) {
+                if (pt->as_named_type() != nullptr) {
                     decl = pt->as_named_type()->declared_type();
                 }
             }
@@ -1991,7 +1991,7 @@ IfcUtil::IfcBaseClass* IfcFile::addEntity(IfcUtil::IfcBaseClass* entity, int id)
                 IfcWrite::IfcWriteArgument* copy = new IfcWrite::IfcWriteArgument();
                 copy->set(new_instances);
                 we->setArgument(i, copy);
-            } else if (decl && decl->is(*schema()->declaration_by_name("IfcLengthMeasure"))) {
+            } else if ((decl != nullptr) && decl->is(*schema()->declaration_by_name("IfcLengthMeasure"))) {
                 if (boost::math::isnan(conversion_factor)) {
                     std::pair<IfcUtil::IfcBaseClass*, double> this_file_unit = {nullptr, 1.0};
                     std::pair<IfcUtil::IfcBaseClass*, double> other_file_unit = {nullptr, 1.0};
@@ -2000,7 +2000,7 @@ IfcUtil::IfcBaseClass* IfcFile::addEntity(IfcUtil::IfcBaseClass* entity, int id)
                         other_file_unit = other_file->getUnit("LENGTHUNIT");
                     } catch (IfcParse::IfcException&) {
                     }
-                    if (this_file_unit.first && other_file_unit.first) {
+                    if ((this_file_unit.first != nullptr) && (other_file_unit.first != nullptr)) {
                         conversion_factor = other_file_unit.second / this_file_unit.second;
                     } else {
                         conversion_factor = 1.;
@@ -2041,7 +2041,7 @@ IfcUtil::IfcBaseClass* IfcFile::addEntity(IfcUtil::IfcBaseClass* entity, int id)
         // A new entity instance name is generated and
         // the instance is pointed to this file.
         we->file = this;
-        if (we->type()->as_entity()) {
+        if (we->type()->as_entity() != nullptr) {
             if (id == -1) {
                 we->set_id(FreshId());
             } else {
@@ -2073,7 +2073,7 @@ IfcUtil::IfcBaseClass* IfcFile::addEntity(IfcUtil::IfcBaseClass* entity, int id)
     // The mapping by entity type is updated.
     const IfcParse::declaration* ty = &new_entity->declaration();
 
-    if (ty->as_entity()) {
+    if (ty->as_entity() != nullptr) {
         aggregate_of_instance::ptr insts = instances_by_type_excl_subtypes(ty);
         if (!insts) {
             insts = aggregate_of_instance::ptr(new aggregate_of_instance());
@@ -2082,7 +2082,7 @@ IfcUtil::IfcBaseClass* IfcFile::addEntity(IfcUtil::IfcBaseClass* entity, int id)
         insts->push(new_entity);
     }
 
-    for (; ty->as_entity();) {
+    for (; ty->as_entity() != nullptr;) {
         aggregate_of_instance::ptr insts = instances_by_type(ty);
         if (!insts) {
             insts = aggregate_of_instance::ptr(new aggregate_of_instance());
@@ -2091,16 +2091,16 @@ IfcUtil::IfcBaseClass* IfcFile::addEntity(IfcUtil::IfcBaseClass* entity, int id)
         insts->push(new_entity);
 
         const IfcParse::declaration* pt = ty->as_entity()->supertype();
-        if (pt) {
+        if (pt != nullptr) {
             ty = pt;
         } else {
             break;
         }
     }
 
-    if (ty->as_entity()) {
+    if (ty->as_entity() != nullptr) {
         int new_id = -1;
-        if (!new_entity->data().file) {
+        if (new_entity->data().file == nullptr) {
             // For newly created entities ensure a valid ENTITY_INSTANCE_NAME is set
             new_entity->data().file = this;
             boost::optional<unsigned> id_value;
@@ -2124,7 +2124,7 @@ IfcUtil::IfcBaseClass* IfcFile::addEntity(IfcUtil::IfcBaseClass* entity, int id)
 
         // The mapping by entity instance name is updated.
         byid[new_id] = new_entity;
-    } else if (!new_entity->data().file) {
+    } else if (new_entity->data().file == nullptr) {
         // For non-entity instances, no mappings are updated, but the file
         // pointer has to be set, so that actual copies are created in subsequent
         // times.
@@ -2134,7 +2134,7 @@ IfcUtil::IfcBaseClass* IfcFile::addEntity(IfcUtil::IfcBaseClass* entity, int id)
         byidentity[new_entity->identity()] = new_entity;
     }
 
-    if (parsing_complete_ && ty->as_entity()) {
+    if (parsing_complete_ && (ty->as_entity() != nullptr)) {
         build_inverses_(new_entity);
     }
 
@@ -2213,7 +2213,7 @@ void IfcFile::process_deletion_() {
                         if (instance_list->contains(entity)) {
                             IfcWrite::IfcWriteArgument* copy = new IfcWrite::IfcWriteArgument();
                             instance_list->remove(entity);
-                            if (!instance_list->size() && related_instance->declaration().as_entity()->attribute_by_index(i)->optional()) {
+                            if ((instance_list->size() == 0U) && related_instance->declaration().as_entity()->attribute_by_index(i)->optional()) {
                                 // @todo we can also check the lower bound of the attribute type before setting to null.
                                 copy->set(boost::blank());
                             } else {
@@ -2317,7 +2317,7 @@ void IfcFile::process_deletion_() {
             }
 
             const IfcParse::declaration* pt = ty->as_entity()->supertype();
-            if (pt) {
+            if (pt != nullptr) {
                 ty = pt;
             } else {
                 break;
@@ -2473,7 +2473,7 @@ std::ostream& operator<<(std::ostream& os, const IfcParse::IfcFile& f) {
 
     for (vector_t::const_iterator it = sorted.begin(); it != sorted.end(); ++it) {
         const IfcUtil::IfcBaseClass* e = it->second;
-        if (e->declaration().as_entity()) {
+        if (e->declaration().as_entity() != nullptr) {
             os << e->data().toString(true) << ";" << std::endl;
         }
     }
@@ -2493,7 +2493,7 @@ std::string IfcFile::createTimestamp() const {
     struct tm* ti = localtime(&t);
 
     std::string result = "";
-    if (strftime(buf, 255, "%Y-%m-%dT%H:%M:%S", ti)) {
+    if (strftime(buf, 255, "%Y-%m-%dT%H:%M:%S", ti) != 0U) {
         result = std::string(buf);
     }
 
@@ -2578,7 +2578,7 @@ void IfcFile::setDefaultHeaderValues() {
     std::vector<std::string> file_description, schema_identifiers, empty_vector;
 
     file_description.push_back("ViewDefinition [CoordinationView]");
-    if (schema()) {
+    if (schema() != nullptr) {
         schema_identifiers.push_back(schema()->name());
     }
 
@@ -2648,7 +2648,7 @@ std::pair<IfcUtil::IfcBaseClass*, double> IfcFile::getUnit(const std::string& un
                     return_value.first = siunit = unit;
                 }
 
-                if (siunit) {
+                if (siunit != nullptr) {
                     Argument* prefix = siunit->data().getArgument(
                         siunit->declaration().as_entity()->attribute_index("Prefix"));
 
@@ -2665,11 +2665,11 @@ std::pair<IfcUtil::IfcBaseClass*, double> IfcFile::getUnit(const std::string& un
 
 void IfcParse::IfcFile::build_inverses_(IfcUtil::IfcBaseClass* inst) {
     std::function<void(IfcUtil::IfcBaseClass*, int)> fn = [this, inst](IfcUtil::IfcBaseClass* attr, int idx) {
-        if (attr->declaration().as_entity()) {
+        if (attr->declaration().as_entity() != nullptr) {
             unsigned entity_attribute_id = attr->data().id();
             auto decl = inst->declaration().as_entity();
             byref_excl[entity_attribute_id].push_back(inst->data().id());
-            while (decl) {
+            while (decl != nullptr) {
                 byref[{entity_attribute_id, decl->index_in_schema(), idx}].push_back(inst->data().id());
                 decl = decl->supertype();
             }
diff --git a/src/ifcparse/IfcSchema.cpp b/src/ifcparse/IfcSchema.cpp
index 1a929974f1..a5ff773f71 100644
--- a/src/ifcparse/IfcSchema.cpp
+++ b/src/ifcparse/IfcSchema.cpp
@@ -72,12 +72,12 @@ bool IfcParse::declaration::is(const std::string& name) const {
         return true;
     }
 
-    if (this->as_entity() && this->as_entity()->supertype()) {
+    if ((this->as_entity() != nullptr) && (this->as_entity()->supertype() != nullptr)) {
         return this->as_entity()->supertype()->is(name);
     }
-    if (this->as_type_declaration()) {
+    if (this->as_type_declaration() != nullptr) {
         const IfcParse::named_type* nt = this->as_type_declaration()->declared_type()->as_named_type();
-        if (nt) {
+        if (nt != nullptr) {
             return nt->is(name);
         }
     }
@@ -90,12 +90,12 @@ bool IfcParse::declaration::is(const IfcParse::declaration& decl) const {
         return true;
     }
 
-    if (this->as_entity() && this->as_entity()->supertype()) {
+    if ((this->as_entity() != nullptr) && (this->as_entity()->supertype() != nullptr)) {
         return this->as_entity()->supertype()->is(decl);
     }
-    if (this->as_type_declaration()) {
+    if (this->as_type_declaration() != nullptr) {
         const IfcParse::named_type* nt = this->as_type_declaration()->declared_type()->as_named_type();
-        if (nt) {
+        if (nt != nullptr) {
             return nt->is(decl);
         }
     }
@@ -129,16 +129,16 @@ IfcParse::schema_definition::schema_definition(const std::string& name, const st
     for (std::vector<const declaration*>::iterator it = declarations_.begin(); it != declarations_.end(); ++it) {
         (**it).schema_ = this;
 
-        if ((**it).as_type_declaration()) {
+        if ((**it).as_type_declaration() != nullptr) {
             type_declarations_.push_back((**it).as_type_declaration());
         }
-        if ((**it).as_select_type()) {
+        if ((**it).as_select_type() != nullptr) {
             select_types_.push_back((**it).as_select_type());
         }
-        if ((**it).as_enumeration_type()) {
+        if ((**it).as_enumeration_type() != nullptr) {
             enumeration_types_.push_back((**it).as_enumeration_type());
         }
-        if ((**it).as_entity()) {
+        if ((**it).as_entity() != nullptr) {
             entities_.push_back((**it).as_entity());
         }
     }
@@ -153,7 +153,7 @@ IfcParse::schema_definition::~schema_definition() {
 }
 
 IfcUtil::IfcBaseClass* IfcParse::schema_definition::instantiate(IfcEntityInstanceData* data) const {
-    if (factory_) {
+    if (factory_ != nullptr) {
         return (*factory_)(data);
     }
     return new IfcUtil::IfcLateBoundEntity(data->type(), data);
diff --git a/src/ifcparse/IfcSchema.h b/src/ifcparse/IfcSchema.h
index aad5e1db03..8c66411a81 100644
--- a/src/ifcparse/IfcSchema.h
+++ b/src/ifcparse/IfcSchema.h
@@ -319,7 +319,7 @@ class IFC_PARSE_API entity : public declaration {
 
     const attribute* attribute_by_index_(size_t& index) const {
         const attribute* attr = 0;
-        if (supertype_) {
+        if (supertype_ != nullptr) {
             attr = supertype_->attribute_by_index_(index);
         }
         if (attr == 0) {
@@ -361,7 +361,7 @@ class IFC_PARSE_API entity : public declaration {
     const std::vector<const attribute*> all_attributes() const {
         std::vector<const attribute*> attrs;
         attrs.reserve(derived_.size());
-        if (supertype_) {
+        if (supertype_ != nullptr) {
             const std::vector<const attribute*> supertype_attrs = supertype_->all_attributes();
             std::copy(supertype_attrs.begin(), supertype_attrs.end(), std::back_inserter(attrs));
         }
@@ -371,7 +371,7 @@ class IFC_PARSE_API entity : public declaration {
 
     const std::vector<const inverse_attribute*> all_inverse_attributes() const {
         std::vector<const inverse_attribute*> attrs;
-        if (supertype_) {
+        if (supertype_ != nullptr) {
             const std::vector<const inverse_attribute*> supertype_inv_attrs = supertype_->all_inverse_attributes();
             std::copy(supertype_inv_attrs.begin(), supertype_inv_attrs.end(), std::back_inserter(attrs));
         }
@@ -389,7 +389,7 @@ class IFC_PARSE_API entity : public declaration {
 
     size_t attribute_count() const {
         size_t super_count = 0;
-        if (supertype_) {
+        if (supertype_ != nullptr) {
             super_count = supertype_->attribute_count();
         }
         return super_count + attributes_.size();
diff --git a/src/ifcparse/IfcSpfHeader.cpp b/src/ifcparse/IfcSpfHeader.cpp
index 588e125048..625b2d52a3 100644
--- a/src/ifcparse/IfcSpfHeader.cpp
+++ b/src/ifcparse/IfcSpfHeader.cpp
@@ -40,7 +40,7 @@ HeaderEntity::HeaderEntity(const char* const datatype, size_t size, IfcFile* fil
     : IfcEntityInstanceData(file, size),
       _datatype(datatype),
       size_(size) {
-    if (file) {
+    if (file != nullptr) {
         offset_in_file_ = file->stream->Tell();
         load();
     }
@@ -131,45 +131,45 @@ void IfcSpfHeader::write(std::ostream& os) const {
 }
 
 const FileDescription& IfcSpfHeader::file_description() const {
-    if (_file_description) {
-        return *_file_description;
+    if (_file_description == nullptr) {
+        throw IfcException("File description not set");
     }
-    throw IfcException("File description not set");
+    return *_file_description;
 }
 
 const FileName& IfcSpfHeader::file_name() const {
-    if (_file_name) {
-        return *_file_name;
+    if (_file_name == nullptr) {
+        throw IfcException("File name not set");
     }
-    throw IfcException("File name not set");
+    return *_file_name;
 }
 
 const FileSchema& IfcSpfHeader::file_schema() const {
-    if (_file_schema) {
-        return *_file_schema;
+    if (_file_schema == nullptr) {
+        throw IfcException("File schema not set");
     }
-    throw IfcException("File schema not set");
+    return *_file_schema;
 }
 
 FileDescription& IfcSpfHeader::file_description() {
-    if (_file_description) {
-        return *_file_description;
+    if (_file_description == nullptr) {
+        throw IfcException("File description not set");
     }
-    throw IfcException("File description not set");
+    return *_file_description;
 }
 
 FileName& IfcSpfHeader::file_name() {
-    if (_file_name) {
-        return *_file_name;
+    if (_file_name == nullptr) {
+        throw IfcException("File name not set");
     }
-    throw IfcException("File name not set");
+    return *_file_name;
 }
 
 FileSchema& IfcSpfHeader::file_schema() {
-    if (_file_schema) {
-        return *_file_schema;
+    if (_file_schema == nullptr) {
+        throw IfcException("File schema not set");
     }
-    throw IfcException("File schema not set");
+    return *_file_schema;
 }
 
 FileDescription::FileDescription(IfcFile* file) : HeaderEntity(FILE_DESCRIPTION, 2, file) {}
diff --git a/src/ifcparse/IfcUtil.cpp b/src/ifcparse/IfcUtil.cpp
index 81c944e233..57fba2eebd 100644
--- a/src/ifcparse/IfcUtil.cpp
+++ b/src/ifcparse/IfcUtil.cpp
@@ -62,14 +62,14 @@
 #include <boost/optional.hpp>
 
 void aggregate_of_instance::push(IfcUtil::IfcBaseClass* l) {
-    if (l) {
+    if (l != nullptr) {
         ls.push_back(l);
     }
 }
 void aggregate_of_instance::push(const aggregate_of_instance::ptr& l) {
     if (l) {
         for (it i = l->begin(); i != l->end(); ++i) {
-            if (*i) {
+            if (*i != nullptr) {
                 ls.push_back(*i);
             }
         }
@@ -253,23 +253,23 @@ IfcUtil::ArgumentType IfcUtil::from_parameter_type(const IfcParse::parameter_typ
     const IfcParse::named_type* nt = pt->as_named_type();
     const IfcParse::simple_type* st = pt->as_simple_type();
 
-    if (at) {
+    if (at != nullptr) {
         return make_aggregate(from_parameter_type(at->type_of_element()));
     }
-    if (nt) {
-        if (nt->declared_type()->as_entity()) {
+    if (nt != nullptr) {
+        if (nt->declared_type()->as_entity() != nullptr) {
             return IfcUtil::Argument_ENTITY_INSTANCE;
         }
-        if (nt->declared_type()->as_enumeration_type()) {
+        if (nt->declared_type()->as_enumeration_type() != nullptr) {
             return IfcUtil::Argument_ENUMERATION;
         }
-        if (nt->declared_type()->as_select_type()) {
+        if (nt->declared_type()->as_select_type() != nullptr) {
             return IfcUtil::Argument_ENTITY_INSTANCE;
         }
-        if (nt->declared_type()->as_type_declaration()) {
+        if (nt->declared_type()->as_type_declaration() != nullptr) {
             return from_parameter_type(nt->declared_type()->as_type_declaration()->declared_type());
         }
-    } else if (st) {
+    } else if (st != nullptr) {
         switch (st->declared_type()) {
         case IfcParse::simple_type::binary_type:
             return IfcUtil::Argument_BINARY;
@@ -336,7 +336,7 @@ IFC_PARSE_API bool IfcUtil::path::rename_file(const std::string& old_filename, c
 }
 
 IFC_PARSE_API bool IfcUtil::path::delete_file(const std::string& filename) {
-    return std::remove(filename.c_str());
+    return std::remove(filename.c_str()) != 0;
 }
 
 #endif
diff --git a/src/ifcparse/IfcWrite.cpp b/src/ifcparse/IfcWrite.cpp
index c660ac4d76..3b2cb4e577 100644
--- a/src/ifcparse/IfcWrite.cpp
+++ b/src/ifcparse/IfcWrite.cpp
@@ -145,7 +145,7 @@ class StringBuilderVisitor : public boost::static_visitor<void> {
     }
     void operator()(const IfcUtil::IfcBaseClass* const& i) {
         const IfcEntityInstanceData& e = i->data();
-        if (!e.type()->as_entity()) {
+        if (e.type()->as_entity() == nullptr) {
             data << e.toString(upper);
         } else {
             data << "#" << e.id();
@@ -309,7 +309,7 @@ void IfcWriteArgument::set(const aggregate_of_aggregate_of_instance::ptr& v) {
 
 // Overload to detect null values
 void IfcWriteArgument::set(IfcUtil::IfcBaseInterface* const& v) {
-    if (v) {
+    if (v != nullptr) {
         container = v->as<IfcUtil::IfcBaseClass>();
     } else {
         container = boost::blank();
diff --git a/src/ifcparse/parse_ifcxml.cpp b/src/ifcparse/parse_ifcxml.cpp
index e943ccbb1a..93e4ca7c01 100644
--- a/src/ifcparse/parse_ifcxml.cpp
+++ b/src/ifcparse/parse_ifcxml.cpp
@@ -45,8 +45,8 @@ enum ifcxml_dialect {
 // "Dereferences" a named_attribute. For example:
 // IfcCompoundPlaneAngleMeasure -> LIST [3:4] OF INTEGER
 void follow_named(const IfcParse::parameter_type*& pt) {
-    while (pt->as_named_type()) {
-        if (pt->as_named_type()->declared_type()->as_type_declaration()) {
+    while (pt->as_named_type() != nullptr) {
+        if (pt->as_named_type()->declared_type()->as_type_declaration() != nullptr) {
             pt = pt->as_named_type()->declared_type()->as_type_declaration()->declared_type();
         } else {
             break;
@@ -164,7 +164,7 @@ class stack_node {
         std::stringstream ss;
         static const char* const node_type_names[] = {"empty", "inst", "attr", "aggr", "agelem", "inv", "sel", "head", "hdentry"};
         ss << "[" << node_type_names[type_] << "] ";
-        if (inst_) {
+        if (inst_ != nullptr) {
             ss << inst_->declaration().name() << " ";
         }
         if (type_ == node_aggregate) {
@@ -288,7 +288,7 @@ static void process_characters(void* user, const xmlChar* ch, int len) {
         state_type = state->stack.back().ntype();
     }
 
-    if (!state->stack.empty() && state->stack.back().inst() != nullptr && state->stack.back().inst()->declaration().as_type_declaration()) {
+    if (!state->stack.empty() && state->stack.back().inst() != nullptr && (state->stack.back().inst()->declaration().as_type_declaration() != nullptr)) {
         auto pt = state->stack.back().inst()->declaration().as_type_declaration()->declared_type();
         Argument* val = nullptr;
         try {
@@ -296,7 +296,7 @@ static void process_characters(void* user, const xmlChar* ch, int len) {
         } catch (const std::exception& e) {
             Logger::Error(e, state->stack.back().inst());
         }
-        if (val) {
+        if (val != nullptr) {
             // type declaration always at idx 0
             state->stack.back().inst()->data().setArgument(0, val);
         }
@@ -327,14 +327,14 @@ static void process_characters(void* user, const xmlChar* ch, int len) {
         auto cpp_type = IfcUtil::from_parameter_type(pt);
         if (cpp_type != IfcUtil::Argument_ENTITY_INSTANCE) {
             auto val = parse_attribute_value(pt, txt);
-            if (val) {
+            if (val != nullptr) {
                 state->stack.back().inst()->data().setArgument(state->stack.back().idx(), val);
             }
         }
     } else if (state_type == stack_node::node_aggregate_element) {
         auto pt = state->stack.back().aggregate_elem_type();
         auto val = parse_attribute_value(pt, txt);
-        if (val) {
+        if (val != nullptr) {
             (*(state->stack.rbegin() + 1)).aggregate_elements.push_back(val);
         }
     }
@@ -357,11 +357,11 @@ static void start_element(void* user, const xmlChar* tag, const xmlChar** attrs)
 
     std::vector<std::pair<std::string, std::string>> attributes;
 
-    if (attrs) {
+    if (attrs != nullptr) {
         std::string attrname;
         int i = 0;
         while (attrs[i] != NULL) {
-            if (i % 2) {
+            if ((i % 2) != 0) {
                 const std::string value = (char*)attrs[i];
 #ifndef NDEBUG
                 std::cout << " " << attrname << "='" << value << "'";
@@ -444,10 +444,9 @@ static void start_element(void* user, const xmlChar* tag, const xmlChar** attrs)
                         if (state->idmap.find(pair.second) == state->idmap.end()) {
                             rv = pair.second;
                             return rv;
-                        } else {
-                            rv = state->file->instance_by_id(state->idmap[pair.second]);
-                            return rv;
                         }
+                        rv = state->file->instance_by_id(state->idmap[pair.second]);
+                        return rv;
                     }
                 } else if (pair.first == "xsi:type") {
                     decl = state->file->schema()->declaration_by_name(pair.second)->as_entity();
@@ -457,7 +456,7 @@ static void start_element(void* user, const xmlChar* tag, const xmlChar** attrs)
             auto untyped = new IfcEntityInstanceData(decl);
 
             const IfcParse::entity* entity = decl->as_entity();
-            if (entity) {
+            if (entity != nullptr) {
                 for (auto& pair : attributes) {
                     if (pair.first == "id" || pair.first == "xsi:type" || pair.first == "pos") {
                         continue;
@@ -467,7 +466,7 @@ static void start_element(void* user, const xmlChar* tag, const xmlChar** attrs)
                     if (idx != -1) {
                         auto attr = entity->attribute_by_index(idx);
                         auto val = parse_attribute_value(attr->type_of_attribute(), pair.second);
-                        if (val) {
+                        if (val != nullptr) {
                             untyped->setArgument(idx, val);
                         }
                     } else {
@@ -522,7 +521,7 @@ static void start_element(void* user, const xmlChar* tag, const xmlChar** attrs)
 			boost::lexical_cast<int>(it->second);
 			*/
 
-            if (element_type->as_simple_type()) {
+            if (element_type->as_simple_type() != nullptr) {
                 state->stack.push_back(stack_node::aggregate_element(element_type, aggrpos));
             } else {
                 const IfcParse::declaration* decl = nullptr;
@@ -531,7 +530,7 @@ static void start_element(void* user, const xmlChar* tag, const xmlChar** attrs)
                 } catch (const std::exception& e) {
                     Logger::Error(e);
                 }
-                if (decl) {
+                if (decl != nullptr) {
                     auto inst_or_ref = create_instance(decl);
                     IfcUtil::IfcBaseClass* inst;
                     Argument* attr;
@@ -581,7 +580,7 @@ static void start_element(void* user, const xmlChar* tag, const xmlChar** attrs)
                     const IfcParse::parameter_type* attribute_type = current->attribute_by_index(idx)->type_of_attribute();
                     if (state->dialect == ifcxml_dialect_ifc2x3) {
                         follow_named(attribute_type);
-                        if (attribute_type->as_aggregation_type()) {
+                        if (attribute_type->as_aggregation_type() != nullptr) {
                             state->stack.push_back(stack_node::aggregate(state->stack.back().inst(), idx));
                         } else {
                             state->stack.push_back(stack_node::instance_attribute(state->stack.back().inst(), idx));
@@ -595,17 +594,17 @@ 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 (attribute_type->as_named_type()->declared_type()->as_select_type()) {
+                            } else if (attribute_type->as_named_type()->declared_type()->as_select_type() != nullptr) {
                                 // 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));
                             }
-                        } else if (attribute_type->as_aggregation_type()) {
+                        } else if (attribute_type->as_aggregation_type() != nullptr) {
                             state->stack.push_back(stack_node::aggregate(state->stack.back().inst(), idx));
                         }
                     }
                 }
             }
-        } else if (state->file) {
+        } else if (state->file != nullptr) {
             if (state_type == stack_node::node_header) {
                 state->stack.push_back(stack_node::header_entry(tagname));
             } else if (tagname == "ex:iso_10303_28_header" || tagname == "header") {
@@ -620,12 +619,12 @@ static void start_element(void* user, const xmlChar* tag, const xmlChar** attrs)
                     Logger::Error(e);
                 }
 
-                if (!decl) {
+                if (decl == nullptr) {
                     goto end;
                 }
 
                 const IfcParse::entity* entity = decl->as_entity();
-                if (!entity && state_type != stack_node::node_instance_attribute) {
+                if ((entity == nullptr) && state_type != stack_node::node_instance_attribute) {
                     Logger::Error("Not an entity definition " + tagname);
                     goto end;
                 }
@@ -640,7 +639,7 @@ static void start_element(void* user, const xmlChar* tag, const xmlChar** attrs)
                         state->stack.back().inv_attr()->attribute_reference());
                     IfcWrite::IfcWriteArgument* attr_inv = new IfcWrite::IfcWriteArgument();
                     attr_inv->set(state->stack.back().inst());
-                    if (inst) {
+                    if (inst != nullptr) {
                         inst->data().setArgument(idx, attr_inv);
                     } else {
                         Logger::Error("Internal error, inverse attribute not processed");
@@ -689,7 +688,7 @@ IFC_PARSE_API IfcParse::IfcFile* IfcParse::parse_ifcxml(const std::string& filen
         }
     }
 
-    if (state.file) {
+    if (state.file != nullptr) {
         state.file->parsing_complete() = true;
         state.file->build_inverses();
     }