Sparse, the semantic parser, provides a compiler frontend capable of parsing most of ANSI C as well as many GCC extensions, and a collection of sample compiler backends, including a static analyzer also called "sparse". Sparse provides a set of annotations designed to convey semantic information about types, such as what address space pointers point to, or what locks a function acquires or releases. Linus Torvalds started writing Sparse in 2003, initially targeting issues such as mixing pointers to user address space and pointers to kernel address space. As of 2006, Josh Triplett now maintains Sparse.