diff --git a/src/xml/xml_native_reader.cc b/src/xml/xml_native_reader.cc
index d467a12d..03ec1a44 100644
--- a/src/xml/xml_native_reader.cc
+++ b/src/xml/xml_native_reader.cc
@@ -985,25 +985,25 @@ void mjXReader::Parse(XMLElement* root, const mjVFS* vfs) {
 
 
 // compiler section parser
-void mjXReader::Compiler(XMLElement* section, mjSpec* spec) {
+void mjXReader::Compiler(XMLElement* section, mjSpec* s) {
   string text;
   int n;
 
   // top-level attributes
   if (MapValue(section, "autolimits", &n, bool_map, 2)) {
-    spec->compiler.autolimits = (n == 1);
+    s->compiler.autolimits = (n == 1);
   }
-  ReadAttr(section, "boundmass", 1, &spec->compiler.boundmass, text);
-  ReadAttr(section, "boundinertia", 1, &spec->compiler.boundinertia, text);
-  ReadAttr(section, "settotalmass", 1, &spec->compiler.settotalmass, text);
+  ReadAttr(section, "boundmass", 1, &s->compiler.boundmass, text);
+  ReadAttr(section, "boundinertia", 1, &s->compiler.boundinertia, text);
+  ReadAttr(section, "settotalmass", 1, &s->compiler.settotalmass, text);
   if (MapValue(section, "balanceinertia", &n, bool_map, 2)) {
-    spec->compiler.balanceinertia = (n == 1);
+    s->compiler.balanceinertia = (n == 1);
   }
   if (MapValue(section, "strippath", &n, bool_map, 2)) {
-    spec->strippath = (n == 1);
+    s->strippath = (n == 1);
   }
   if (MapValue(section, "fitaabb", &n, bool_map, 2)) {
-    spec->compiler.fitaabb = (n == 1);
+    s->compiler.fitaabb = (n == 1);
   }
   if (MapValue(section, "coordinate", &n, coordinate_map, 2)) {
     if (n == 1) {
@@ -1012,48 +1012,48 @@ void mjXReader::Compiler(XMLElement* section, mjSpec* spec) {
     }
   }
   if (MapValue(section, "angle", &n, angle_map, 2)) {
-    spec->compiler.degree = (n == 1);
+    s->compiler.degree = (n == 1);
   }
   if (ReadAttrTxt(section, "eulerseq", text)) {
     if (text.size() != 3) {
       throw mjXError(section, "euler format must have length 3");
     }
-    memcpy(spec->compiler.eulerseq, text.c_str(), 3);
+    memcpy(s->compiler.eulerseq, text.c_str(), 3);
   }
   if (ReadAttrTxt(section, "assetdir", text)) {
-    mjs_setString(spec->meshdir, text.c_str());
-    mjs_setString(spec->texturedir, text.c_str());
+    mjs_setString(s->meshdir, text.c_str());
+    mjs_setString(s->texturedir, text.c_str());
   }
   // meshdir and texturedir take precedence over assetdir
   string meshdir, texturedir;
   if (ReadAttrTxt(section, "meshdir", meshdir)) {
-    mjs_setString(spec->meshdir, meshdir.c_str());
+    mjs_setString(s->meshdir, meshdir.c_str());
   };
   if (ReadAttrTxt(section, "texturedir", texturedir)) {
-    mjs_setString(spec->texturedir, texturedir.c_str());
+    mjs_setString(s->texturedir, texturedir.c_str());
   }
   if (MapValue(section, "discardvisual", &n, bool_map, 2)) {
-    spec->compiler.discardvisual = (n == 1);
+    s->compiler.discardvisual = (n == 1);
   }
   if (MapValue(section, "usethread", &n, bool_map, 2)) {
-    spec->compiler.usethread = (n == 1);
+    s->compiler.usethread = (n == 1);
   }
   if (MapValue(section, "fusestatic", &n, bool_map, 2)) {
-    spec->compiler.fusestatic = (n == 1);
+    s->compiler.fusestatic = (n == 1);
   }
-  MapValue(section, "inertiafromgeom", &spec->compiler.inertiafromgeom, TFAuto_map, 3);
-  ReadAttr(section, "inertiagrouprange", 2, spec->compiler.inertiagrouprange, text);
+  MapValue(section, "inertiafromgeom", &s->compiler.inertiafromgeom, TFAuto_map, 3);
+  ReadAttr(section, "inertiagrouprange", 2, s->compiler.inertiagrouprange, text);
   if (MapValue(section, "alignfree", &n, bool_map, 2)) {
-    spec->compiler.alignfree = (n == 1);
+    s->compiler.alignfree = (n == 1);
   }
   if (MapValue(section, "saveinertial", &n, bool_map, 2)) {
-    spec->compiler.saveinertial = (n == 1);
+    s->compiler.saveinertial = (n == 1);
   }
 
   // lengthrange subelement
   XMLElement* elem = FindSubElem(section, "lengthrange");
   if (elem) {
-    mjLROpt* opt = &(spec->compiler.LRopt);
+    mjLROpt* opt = &(s->compiler.LRopt);
 
     // flags
     MapValue(elem, "mode", &opt->mode, lrmode_map, lrmode_sz);
@@ -1173,7 +1173,7 @@ void mjXReader::Option(XMLElement* section, mjOption* opt) {
 
 
 // size section parser
-void mjXReader::Size(XMLElement* section, mjSpec* spec) {
+void mjXReader::Size(XMLElement* section, mjSpec* s) {
   // read memory bytes
   {
     constexpr char err_msg[] =
@@ -1262,69 +1262,69 @@ void mjXReader::Size(XMLElement* section, mjSpec* spec) {
       if (*memory / sizeof(mjtNum) > std::numeric_limits<std::size_t>::max()) {
         throw mjXError(section, "%s", err_msg);
       }
-      spec->memory = *memory;
+      s->memory = *memory;
     }
   }
 
   // read sizes
-  ReadAttrInt(section, "nuserdata", &spec->nuserdata);
-  ReadAttrInt(section, "nkey", &spec->nkey);
+  ReadAttrInt(section, "nuserdata", &s->nuserdata);
+  ReadAttrInt(section, "nkey", &s->nkey);
 
-  ReadAttrInt(section, "nconmax", &spec->nconmax);
-  if (spec->nconmax < -1) throw mjXError(section, "nconmax must be >= -1");
+  ReadAttrInt(section, "nconmax", &s->nconmax);
+  if (s->nconmax < -1) throw mjXError(section, "nconmax must be >= -1");
 
   {
     int nstack = -1;
     const bool has_nstack = ReadAttrInt(section, "nstack", &nstack);
     if (has_nstack) {
-      if (spec->nstack < -1) {
+      if (s->nstack < -1) {
         throw mjXError(section, "nstack must be >= -1");
       }
-      if (spec->memory != -1 && nstack != -1) {
+      if (s->memory != -1 && nstack != -1) {
         throw mjXError(section,
                        "either 'memory' and 'nstack' attribute can be specified, not both");
       }
-      spec->nstack = nstack;
+      s->nstack = nstack;
     }
   }
   {
     int njmax = -1;
     const bool has_njmax = ReadAttrInt(section, "njmax", &njmax);
     if (has_njmax) {
-      if (spec->njmax < -1) {
+      if (s->njmax < -1) {
         throw mjXError(section, "njmax must be >= -1");
       }
-      if (spec->memory != -1 && njmax != -1) {
+      if (s->memory != -1 && njmax != -1) {
         throw mjXError(section,
                        "either 'memory' and 'njmax' attribute can be specified, not both");
       }
-      spec->njmax = njmax;
+      s->njmax = njmax;
     }
   }
 
-  ReadAttrInt(section, "nuser_body", &spec->nuser_body);
-  if (spec->nuser_body < -1) throw mjXError(section, "nuser_body must be >= -1");
+  ReadAttrInt(section, "nuser_body", &s->nuser_body);
+  if (s->nuser_body < -1) throw mjXError(section, "nuser_body must be >= -1");
 
-  ReadAttrInt(section, "nuser_jnt", &spec->nuser_jnt);
-  if (spec->nuser_jnt < -1) throw mjXError(section, "nuser_jnt must be >= -1");
+  ReadAttrInt(section, "nuser_jnt", &s->nuser_jnt);
+  if (s->nuser_jnt < -1) throw mjXError(section, "nuser_jnt must be >= -1");
 
-  ReadAttrInt(section, "nuser_geom", &spec->nuser_geom);
-  if (spec->nuser_geom < -1) throw mjXError(section, "nuser_geom must be >= -1");
+  ReadAttrInt(section, "nuser_geom", &s->nuser_geom);
+  if (s->nuser_geom < -1) throw mjXError(section, "nuser_geom must be >= -1");
 
-  ReadAttrInt(section, "nuser_site", &spec->nuser_site);
-  if (spec->nuser_site < -1) throw mjXError(section, "nuser_site must be >= -1");
+  ReadAttrInt(section, "nuser_site", &s->nuser_site);
+  if (s->nuser_site < -1) throw mjXError(section, "nuser_site must be >= -1");
 
-  ReadAttrInt(section, "nuser_cam", &spec->nuser_cam);
-  if (spec->nuser_cam < -1) throw mjXError(section, "nuser_cam must be >= -1");
+  ReadAttrInt(section, "nuser_cam", &s->nuser_cam);
+  if (s->nuser_cam < -1) throw mjXError(section, "nuser_cam must be >= -1");
 
-  ReadAttrInt(section, "nuser_tendon", &spec->nuser_tendon);
-  if (spec->nuser_tendon < -1) throw mjXError(section, "nuser_tendon must be >= -1");
+  ReadAttrInt(section, "nuser_tendon", &s->nuser_tendon);
+  if (s->nuser_tendon < -1) throw mjXError(section, "nuser_tendon must be >= -1");
 
-  ReadAttrInt(section, "nuser_actuator", &spec->nuser_actuator);
-  if (spec->nuser_actuator < -1) throw mjXError(section, "nuser_actuator must be >= -1");
+  ReadAttrInt(section, "nuser_actuator", &s->nuser_actuator);
+  if (s->nuser_actuator < -1) throw mjXError(section, "nuser_actuator must be >= -1");
 
-  ReadAttrInt(section, "nuser_sensor", &spec->nuser_sensor);
-  if (spec->nuser_sensor < -1) throw mjXError(section, "nuser_sensor must be >= -1");
+  ReadAttrInt(section, "nuser_sensor", &s->nuser_sensor);
+  if (s->nuser_sensor < -1) throw mjXError(section, "nuser_sensor must be >= -1");
 }
 
 
diff --git a/src/xml/xml_native_reader.h b/src/xml/xml_native_reader.h
index 1ad53464..88debf6a 100644
--- a/src/xml/xml_native_reader.h
+++ b/src/xml/xml_native_reader.h
@@ -42,9 +42,9 @@ class mjXReader : public mjXBase {
   void SetTextureDir(const std::string& texturedir);
 
   // XML sections embedded in all formats
-  static void Compiler(tinyxml2::XMLElement* section, mjSpec* spec);   // compiler section
-  static void Option(tinyxml2::XMLElement* section, mjOption* opt);    // option section
-  static void Size(tinyxml2::XMLElement* section, mjSpec* spec);       // size section
+  static void Compiler(tinyxml2::XMLElement* section, mjSpec* s);    // compiler section
+  static void Option(tinyxml2::XMLElement* section, mjOption* opt);  // option section
+  static void Size(tinyxml2::XMLElement* section, mjSpec* s);        // size section
 
  private:
   // XML section specific to MJCF