We present mechanisms that enable our compiler-target language, C--, to express four of the best known techniques for implementing exceptions, all within a single, uniform framework. We define the mechanisms precisely, using a formal operational semantics. We also show that exceptions need not require special treatment in the optimizer; by introducing extra dataflow edges, we make standard optimization techniques work even on programs that use exceptions. Our approach clarifies the design space of exception-handling techniques, and it allows a single optimizer to handle a variety of implementation techniques, uniformly. Our ultimate goal is to allow a source-language compiler the freedom to choose its exception-handling policy, while encapsulating the (architecture-dependent) mechanisms and their optimization in an implementation of C-- that can be used by compilers for many source languages.
Related work is on the C-- page