Compiler correctness

In computing, compiler correctness is the branch of computer science that deals with trying to show that a compiler behaves according to its language specification. Techniques include developing the compiler using formal methods and using rigorous testing (often called compiler validation) on an existing compiler.

Compiler validation with formal methods involves a long chain of formal, deductive logic. However, since the tool to find the proof (theorem prover) is implemented in software and is complex, there is a high probability it will contain errors. One approach has been to use a tool that verifies the proof (a proof checker) which because it is much simpler than a proof-finder is less likely to contain errors.

A language described as a subset of C has been formally verified (although no proof was given of its connection to the C Standard), and the proof has been machine checked.

Methods include model checking, formal verification, and provably correct semantics-directed compiler generation.

Testing represents a significant portion of the effort in shipping a compiler, but receives comparatively little coverage in the standard literature. The 1986 edition of Aho, Sethi, & Ullman has a single-page section on compiler testing, with no named examples. The 2006 edition omits the section on testing, but does emphasize its importance: “Optimizing compilers are so difficult to get right that we dare say that no optimizing compiler is completely error-free! Thus, the most important objective in writing a compiler is that it is correct.” Fraser & Hanson 1995 has a brief section on regression testing; source code is available. Bailey & Davidson 2003 cover testing of procedure calls A number of articles confirm that many released compilers have significant code-correctness bugs. Sheridan 2007 is probably the most recent journal article on general compiler testing. Commercial compiler compliance validation suites are available from ACE, Perennial, and Plum-Hall. For most purposes, the largest body of information available on compiler testing are the Fortran and Cobol validation suites.

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