Gordon Stewart will present his Pre-FPO on Monday, May 12 at 9:30am in Room 302 in the Computer Science Building. The members of his committee are: Andrew Appel (advisor); Zhong Shao and David Walker (readers); David August and Sharad Malik (nonreaders). Everyone is invited to attend his talk. The talk title and abstract follow below: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Title: Verified Separate Compilation for C ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Verified separate compilation is the process of independently translating a program's components in a way that preserves correctness of the program as a whole. In the most general case, a verified separate compiler supports heterogeneous source programs, in which some modules are in C or another high-level language while others are written in a lower-level language like x86 assembly, as is common in systems software such as operating systems. A verified separate compiler in this context is one that preserves the behavior of the entire source program, comprising the C and x86 modules, when the C code is compiled to assembly. Separate compilation has numerous practical benefits. It speeds up development cycles by enabling re-compilation of just those source modules that have been edited by the programmer. It enables shared libraries---separately compiled modules mapped at runtime into the virtual address spaces of multiple processes. It promotes modularity in the large, by enabling programmers to write applications containing logically distinct translation units, each composed at a different level of abstraction or even in a different programming language altogether. But perhaps equally important are applications of verified separate compilers to /modular verification/, the act of reasoning independently about each module in a program (with respect to specifications of the other modules) in order to prove whole program correctness. A modular verification approach means the programmer can break the task of proving correctness of large programs into smaller, more manageable steps: First provide specifications of the modules that form the program, then prove independently of each module that the module meets its specification. When modules proved correct in this way are compiled by a semantics-preserving separate compiler, one gets not only that each module is translated correctly to assembly and then machine code, but also that the target whole program---linked and running on the machine---has the same behavior as the source whole program about which the programmer proved a correctness specification. The result is an end-to-end system: Whole program properties proved modularly at the source level are true also of the whole program that results from separate compilation and linking. In this thesis, I present techniques that address the verified separate compilation problem in the context of C-like languages. My work extends state-of-the-art verified compilers for C such as CompCert (http://compcert.inria.fr/)---the correctness proof of which is currently limited to whole programs---to support verified separate compilation. Major results of the thesis are the proof of a separate compilation theorem for C and the novel semantics of inter-language linking on which the statement of the separate compilation theorem depends. I also address applications to verified compilation of coarse-grained concurrent programs, revealing surprising connections between separate compilation and concurrency in the process. To validate the separate compilation result, I show that it supports modular verification of source programs in the Verified Software Toolchain program logic for C (http://vst.cs.princeton.edu/).