fix: support base components in offsetof expressions

ClangAstParser/src/pt/up/fe/specs/clang/parsers/data/ClavaDataParsers.java

@@ -60,6 +60,7 @@
 import pt.up.fe.specs.clava.ast.expr.data.designator.Designator;
 import pt.up.fe.specs.clava.ast.expr.data.designator.FieldDesignator;
 import pt.up.fe.specs.clava.ast.expr.data.offsetof.OffsetOfArray;
+import pt.up.fe.specs.clava.ast.expr.data.offsetof.OffsetOfBase;
 import pt.up.fe.specs.clava.ast.expr.data.offsetof.OffsetOfComponent;
 import pt.up.fe.specs.clava.ast.expr.data.offsetof.OffsetOfComponentKind;
 import pt.up.fe.specs.clava.ast.expr.data.offsetof.OffsetOfField;
@@ -459,6 +460,9 @@ public static OffsetOfComponent offsetOfComponent(LineStream lines, ClangAstData
         case IDENTIFIER:
             component.set(OffsetOfIdentifier.FIELD_NAME, lines.nextLine());
             break;
+        case BASE:
+            parserData.getClavaNodes().queueSetNode(component, OffsetOfBase.TYPE, lines.nextLine());
+            break;
         default:
             throw new NotImplementedException(kind);
         }

ClavaAst/src/pt/up/fe/specs/clava/ast/expr/OffsetOfExpr.java

@@ -50,18 +50,20 @@ private String getComponentsCode() {
 
         StringBuilder code = new StringBuilder();
 
-        boolean isFirst = true;
+        boolean hasCode = false;
         for (OffsetOfComponent component : get(COMPONENTS)) {
+            String componentCode = component.getCode();
 
-            if (component.isField() && !isFirst) {
-                code.append(".");
+            if (componentCode.isEmpty()) {
+                continue;
             }
 
-            code.append(component.getCode());
-
-            if (isFirst) {
-                isFirst = false;
+            if (component.isField() && hasCode) {
+                code.append(".");
             }
+
+            code.append(componentCode);
+            hasCode = true;
         }
         return code.toString();
     }

ClavaAst/src/pt/up/fe/specs/clava/ast/expr/data/offsetof/OffsetOfBase.java

@@ -0,0 +1,39 @@
+/**
+ * Copyright 2026 SPeCS.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+
+package pt.up.fe.specs.clava.ast.expr.data.offsetof;
+
+import org.suikasoft.jOptions.Datakey.DataKey;
+import org.suikasoft.jOptions.Datakey.KeyFactory;
+
+import pt.up.fe.specs.clava.ast.type.Type;
+
+public class OffsetOfBase extends OffsetOfComponent {
+
+    /// DATAKEYS BEGIN
+
+    public final static DataKey<Type> TYPE = KeyFactory.object("type", Type.class);
+
+    /// DATAKEYS END
+
+    @Override
+    public String getCode() {
+        // Clang adds the base to the semantic path, but it is not part of the source designator.
+        return "";
+    }
+
+    @Override
+    public OffsetOfComponentKind getKind() {
+        return OffsetOfComponentKind.BASE;
+    }
+}

ClavaAst/src/pt/up/fe/specs/clava/ast/expr/data/offsetof/OffsetOfComponent.java

@@ -41,6 +41,8 @@ public static OffsetOfComponent newInstance(OffsetOfComponentKind kind) {
             return new OffsetOfField();
         case IDENTIFIER:
             return new OffsetOfIdentifier();
+        case BASE:
+            return new OffsetOfBase();
         default:
             throw new NotImplementedException(kind);
         }