The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 04, 2001
Filed:
Sep. 15, 1998
David Ungar, Palo Alto, CA (US);
Sun Microsystems, Inc., Palo Alto, CA (US);
Abstract
A method and apparatus for finding bugs related to garbage collection in a virtual machine. For each possible garbage collection point in a stream of execution, a compiler in the virtual machine provides a map that specifies live pointer locations in the stack. In addition, the map identifies those locations in the stack that contain other forms of live data, such as integers. All other locations are considered “dead,” i.e., no longer in use or never used. At each garbage collection point, “dead” locations in the stack are overwritten with an invalid pointer value. Because of the overwriting process, any bug in the compiler that causes a live pointer to be omitted from the map also causes the omitted pointer to be overwritten with the invalid pointer value. Regardless of whether garbage collection is actually performed at the garbage collection point where the pointer was omitted from the compiler-generated map, subsequent execution steps that reference the omitted pointer trigger an invalid pointer error. The invalid pointer error may be trapped and identified as a compiler bug related to map generation in the garbage collection process.