In this paper, we introduce a new parser, called SxLfg, based on the Lexical-Functional Grammars formalism (LFG). We describe the underlying context-free parser and how functional structures are efficiently computed on top of the CFG shared forest thanks to computation sharing, lazy evaluation, and compact data representation. We then present various error recovery techniques we implemented in order to build a robust parser. Finally, we offer concrete results when SxLfg is used with an existing grammar for French. We show that our parser is both efficient and robust, although the grammar is very ambiguous.