This Bugzilla instance is a read-only archive of historic NetBeans bug reports. To report a bug in NetBeans please follow the project's instructions for reporting issues.
I first noticed this warning after updating Netbeans with the latest versions of plug-ins. It only happens during a clean compile and only on those projects compiled with -Xlint. It appears to come from <attribute default="/does/not/exist" name="sourcepath"/> in the -init-macrodef-javac target of the build-impl.xml file.
*** This issue has been marked as a duplicate of 157692 ***