Embedded in Academia

Month: February 2012

  • How Many C Programs Are There?

    If I choose a size S, can you tell me how many valid C programs exist that are no larger than that size? I’m actually interested in the answer — it’ll help me make a point in a paper I’m writing. Shockingly, the Internet (or at least, the part of it that I looked at…

  • Bonneville Salt Flats and Silver Island Mountains

  • C Puzzle: Double Trouble

    I ran into an interesting C program that both of my C oracles (KCC and Frama-C) consider to be well-defined, but that are inconsistently compiled by the current development versions of GCC and Clang on x86-64. The results: [regehr@gamow 1]$ current-gcc -O1 small.c ; ./a.out 1 [regehr@gamow 1]$ current-gcc -O2 small.c ; ./a.out 0 [regehr@gamow…

  • C99 Language Lawyer Needed

    The program below came up during some tests. The question is, is it well-defined by the C99 language? It appears to clearly be undefined behavior by C11 and C++11.

  • Randomly Testing a Static Analyzer

    Static analyzers are intended to find bugs in code, and to show that certain kinds of bugs don’t exist. However, static analyzers are themselves large, complicated programs, leading to a “who watches the watchmen” problem. Pascal Cuoq, one of the people behind the excellent Frama-C analyzer, took it upon himself to run the fuzz-fix cycle…