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Writing Solid Code Week 4
This week most of the students in the class (but not everyone, since we ran out of time) presented their arguments about the quality of various UNIX utility programs. This was a bit more interesting than it might otherwise have been since some of the utilities running on our student lab machines are hilariously old…
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Automatically Entering the Grand C++ Error Explosion Competition
G++ can be comically verbose; developers sometimes like to wallpaper their cubes with choice error messages from Boost or STL programs. The Grand C++ Error Explosion Competition asks the question: how large can we make the ratio between error output and compiler input? I’m not much of a C++ person but when the contest was…
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Writing Solid Code Week 3
This week we finished up the triangle classifier. Not all students’ implementations pass all test cases, which is totally fine with me as long as people learned some lessons about when not to use floating point (I did). On Tuesday we also chose a smallish UNIX utility for each student to evaluate as if it…
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Status of Software Testing
The other day I received a query from some software engineering researchers who are compiling sort of a survey paper about the status of software testing research; here are the questions, with my answers. I’m interested to hear what the rest of you think about this stuff. What do you think are the most significant…
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Writing Solid Code Week 2
First, I wanted to thank everyone for the great discussion on the post about week 1. My single favorite thing about blogging is the discussion and involvement that these posts sometimes generate. During week 2 we worked on issues relating to the triangle classifier. As several commenters predicted, getting correct results using floating point code…
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Writing Solid Code Week 1
This semester I’m teaching a new undergraduate course called Writing Solid Code. The idea is to take a lot of lessons I’ve learned on this subject — testing, debugging, defensive coding, code reviews, etc. — and try to teach it. Since I don’t have any slides or even any lecture notes that are good enough…
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Finding Wrong-Code Bugs in the Wild
Compiler developers already have some decent ways to find bugs: a self-hosting compiler won’t bootstrap if it’s too buggy any serious compiler has a test suite commercial compiler validation suites are available random testcase generators like Csmith and CCG can expose subtle bugs Of course, these tests don’t find all of the bugs. The remaining bugs…
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Reading Iain Banks, Part 1
One of the enduring pleasures of my adult life has been the arrival of a new book by Iain Banks every year or two. Although that is over now, I thought it would be interesting to read his books in order of publication, and to write a bit about each. His first four books were…
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C-Reduce and Frama-C
Yesterday Pascal wrote a nice article addressing practical issues in automated testcase reduction. One issue is that C-Reduce tends to give you what you asked for instead of what you really wanted. Of course, this problem is a common one when performing algorithmic searches. Beyond computer science, the same problem comes up in basically every…
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Informative Assertion Failures
The other day a student was asking me how to make assertion failures in software more informative. I told him there are two pretty easy ways to do this. First, define a customized assert that takes two arguments: the predicate and also a description. For example, in the Botan crypto library we see lines like…