Many computing systems today are written in weakly typed languages such as C and C++. These languages are known to be “unsafe ” as they do not prevent or detect common memory errors like array bounds violations, pointer cast errors, etc. The presence of such undetected errors has two major implications. The first problem is that it makes systems written in these languages unreliable and vulnerable to security attacks. The second problem, which has never been solved for ordinary C, is that it prevents sound, sophisticated static analyses from being reliably applied to these programs. Despite these known problems, increasingly complex software continues to get written in these languages because of performance and backwards-compatibility considerations. This thesis presents a new compiler and a run-time system called SAFECode (Static Analysis For safe Execution of Code) that addresses these two problems. First, SAFECode guarantees memory safety for programs in unsafe languages with very low overhead. Second, SAFECode provides a platform for reliable static analyses by ensuring that an aggressive interprocedural pointer