Month: February 2017

  • Teaching Python Informally to Kids

    For the last few months I’ve been running a “coding club” for my son’s sixth-grade class. Once a week, the interested students (about 2/3 of the class) stick around for an hour after school and I help them learn to program. The structure is basically like the lab part of a programming class, without the…

  • Undefined Behavior != Unsafe Programming

    Undefined behavior (UB) in C and C++ is a clear and present danger to developers, especially when they are writing code that will execute near a trust boundary. A less well-known kind of undefined behavior exists in the intermediate representation (IR) for most optimizing, ahead-of-time compilers. For example, LLVM IR has undef and poison in…

  • Nine Mile Canyon

    One of my boys and I spent Sunday exploring Nine Mile Canyon, in the remote Book Cliffs a few hours drive from Salt Lake City. This canyon is known for its dense collection of rock art and ruins, a lot of which can be seen from the paved road that follows the canyon bottom. This…

  • Detecting Strict Aliasing Violations in the Wild

    Type-based alias analysis, where pointers to different types are assumed to point to distinct objects, gives compilers a simple and effective way to disambiguate memory references in order to generate better code. Unfortunately, C and C++ make it easy for programmers to violate the assumptions upon which type-based alias analysis is built. “Strict aliasing” refers…