### Eclipse Workspace Patch 1.0
#P org.eclipse.jdt.core
Index: model/org/eclipse/jdt/internal/core/ClasspathEntry.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/ClasspathEntry.java,v
retrieving revision 1.117
diff -u -r1.117 ClasspathEntry.java
--- model/org/eclipse/jdt/internal/core/ClasspathEntry.java	21 Apr 2009 04:39:55 -0000	1.117
+++ model/org/eclipse/jdt/internal/core/ClasspathEntry.java	21 Jul 2009 07:45:23 -0000
@@ -1960,6 +1960,12 @@
 	private static IJavaModelStatus validateLibraryEntry(IPath path, IJavaProject project, String container, IPath sourceAttachment, String entryPathMsg) {
 		if (path.isAbsolute() && !path.isEmpty()) {
 			Object target = JavaModel.getTarget(path, true);
+			if (target == null) { // https://bugs.eclipse.org/bugs/show_bug.cgi?id=248661
+				IPath workspaceRoot = ResourcesPlugin.getWorkspace().getRoot().getLocation();
+				if (workspaceRoot.isPrefixOf(path)) {
+					target = JavaModel.getTarget(path.makeRelativeTo(workspaceRoot).makeAbsolute(), true);
+				}
+			}
 			if (target != null && !JavaCore.IGNORE.equals(project.getOption(JavaCore.CORE_INCOMPATIBLE_JDK_LEVEL, true))) {
 				long projectTargetJDK = CompilerOptions.versionToJdkLevel(project.getOption(JavaCore.COMPILER_CODEGEN_TARGET_PLATFORM, true));
 				long libraryJDK = Util.getJdkLevel(target);