diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/GCCCompleteParseExtensionsTest.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/GCCCompleteParseExtensionsTest.java
index 16fb32bfea9..495b19abb49 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/GCCCompleteParseExtensionsTest.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/GCCCompleteParseExtensionsTest.java
@@ -381,4 +381,31 @@ public class GCCCompleteParseExtensionsTest extends AST2BaseTest {
         parseGPP( writer.toString() );
     }
 	
+	// typedef int size_t;  // will be defined in <stddef.h>
+	// struct S {int m;};
+	// void test() {
+	//    int a= __builtin_offsetof(struct S, m);  
+	// };
+	public void test__builtinOffsetof_Bug265001() throws Exception {
+		// gcc with __GNUC__ >= 4 defines:
+		// #define offsetof(type, field) __builtin_offsetof(type, field)
+
+		String code= getAboveComment();
+		parseGCC(code);
+		parseGPP(code);
+	}
+
+	// typedef struct S {int m;} T;
+	// void test() {
+	//    int a= __offsetof__(1);           
+	// };
+	public void test__offsetof__Bug265001() throws Exception {
+		// gcc with __GNUC__ < 4 defines:
+		//		#define offsetof(type, field)					\
+		//		(__offsetof__ (reinterpret_cast <__size_t>		\
+		//			 (& reinterpret_cast <const volatile char &>	\
+		//			  (static_cast<type *> (0)->field))))
+		String code= getAboveComment();
+		parseGPP(code);
+	}
 }
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/GNUScannerExtensionConfiguration.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/GNUScannerExtensionConfiguration.java
index edb9211a80a..a5b6acdd0b7 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/GNUScannerExtensionConfiguration.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/GNUScannerExtensionConfiguration.java
@@ -40,7 +40,8 @@ public abstract class GNUScannerExtensionConfiguration extends AbstractScannerEx
 		addMacro("__builtin_va_arg(ap,type)", "*(type *)ap");
 		addMacro("__builtin_constant_p(exp)", "0");
 		addMacro("__builtin_types_compatible_p(x,y)", "__builtin_types_compatible_p(sizeof(x),sizeof(y))");
-		
+		addMacro("__offsetof__(x)", "(x)");
+
     	addPreprocessorKeyword(Keywords.cINCLUDE_NEXT, IPreprocessorDirective.ppInclude_next); 
     	addPreprocessorKeyword(Keywords.cIMPORT, IPreprocessorDirective.ppImport);
     	addPreprocessorKeyword(Keywords.cWARNING, IPreprocessorDirective.ppWarning);
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/c/GCCScannerExtensionConfiguration.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/c/GCCScannerExtensionConfiguration.java
index 02612b6c5e3..30d89ec03ab 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/c/GCCScannerExtensionConfiguration.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/c/GCCScannerExtensionConfiguration.java
@@ -28,9 +28,11 @@ public class GCCScannerExtensionConfiguration extends GNUScannerExtensionConfigu
 		return sInstance;
 	}
 
+	@SuppressWarnings("nls")
 	public GCCScannerExtensionConfiguration() {
-		addMacro("__null", "(void *)0");  //$NON-NLS-1$//$NON-NLS-2$
-		addMacro("_Pragma(arg)", "");  //$NON-NLS-1$//$NON-NLS-2$
+		addMacro("__null", "(void *)0");  
+		addMacro("_Pragma(arg)", "");  
+		addMacro("__builtin_offsetof(T,m)", "((size_t) &((T *)0)->m)");
 	}
 
     /* (non-Javadoc)
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/cpp/GPPScannerExtensionConfiguration.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/cpp/GPPScannerExtensionConfiguration.java
index d3f8db54758..009359517c7 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/cpp/GPPScannerExtensionConfiguration.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/parser/cpp/GPPScannerExtensionConfiguration.java
@@ -31,8 +31,10 @@ public class GPPScannerExtensionConfiguration extends GNUScannerExtensionConfigu
 		return sInstance;
 	}
 	
+	@SuppressWarnings("nls")
 	public GPPScannerExtensionConfiguration() {
-		addMacro("__null", "0");  //$NON-NLS-1$//$NON-NLS-2$
+		addMacro("__null", "0");  
+		addMacro("__builtin_offsetof(T,m)", "(reinterpret_cast <size_t>(&reinterpret_cast <const volatile char &>(static_cast<T*> (0)->m)))");
 		addKeyword(Keywords.c_COMPLEX, IToken.t__Complex);
 		addKeyword(Keywords.c_IMAGINARY, IToken.t__Imaginary);
 	}