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Why Not Mix Signed and Unsigned Values in C/C++?
Most C/C++ programmers have been told to avoid mixing signed and unsigned values in expressions. However — at least in part because we usually follow this advice — many of us are not totally on top of the underlying issues. This program illustrates what can go wrong: #include <stdio.h> int main (void) { long…
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Giving a Talk at the GCC Summit
Last month I proposed giving a paper presentation at the next GCC Developers’ Summit about our compiler bug finding work. Happily, it was accepted and in late October I’ll head up to Ottawa to tell them what we’ve been doing and what we plan to do. Here’s the abstract: About 60 wrong-code and crash bugs…
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Strange Utah
Pretty much anyone in the world who knows that Utah exists, knows that Utah is weird. Outsiders have vague and usually uninformed — but nevertheless strong — feelings about Utah. Residents have more concrete information. The proper reaction is not to deny, marginalize, or rationalize Utah’s weirdness. The proper reaction is to embrace it, because…
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Static Analysis Fatigue
My student Peng and I have been submitting lots of bug reports to maintainers of open source software packages. These bugs were found using Peng’s integer undefined behavior detector. We’ve found problems in OpenSSL, BIND, Perl, Python, PHP, GMP, GCC, and many others. As we reported these bugs, I noticed developers doing something funny: in…
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Sensor Network Technology in Vinge’s A Deepness in the Sky
An important function of science fiction is to help us understand sociological, technological, and other aspects of our future. A really good SF novel — like some of those produced by Asimov, Clarke, Heinlein, Le Guin, Niven, and Vinge — is so full of ideas and possibilities that the reader’s mind is expanded a little.…
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The Future of Compiler Correctness
Notes: This piece is mainly about compilers used for safety-critical or otherwise-critical systems. The intersection of formal methods and compilers for scripting languages is the empty set. Readers may be interested in a companion piece The Future of Compiler Optimization. A half-century of experience in developing compilers has not resulted in a body of widely-used…