Explaining Code using ASCII Art – Embedded in Academia
People tend to be visual: we use pictures to understand problems. Mainstream programming languages, on the other hand, operate in an almost completely different kind of abstract space, leaving a big gap between programs and pictures. This piece is about pictures drawn using a text character set and then embedded in source code. I love these! The other day I asked around on Twitter for more example
Write Fuzzable Code – Embedded in Academia
Fuzzing is sort of a superpower for locating vulnerabilities and other software defects, but it is often used to find problems baked deeply into already-deployed code. Fuzzing should be done earlier, and moreover developers should spend some effort making their code more amenable to being fuzzed. This post is a non-comprehensive, non-orthogonal list of ways that you can write code that fuzzes bett
How LLVM Optimizes a Function – Embedded in Academia
An optimizing, ahead-of-time compiler is usually structured as: A frontend that converts source code into an intermediate representation (IR). A target-independent optimization pipeline: a sequence of passes that successively rewrite the IR to eliminate inefficiencies and forms that cannot be readily translated into machine code. Sometimes called the “middle end.” A target-dependent backend that g
Testing LLVM – Embedded in Academia
[This piece is loosely a followup to this one.] Background Once a piece of software reaches a certain size, it is guaranteed to be loosely specified and not completely understood by any individual. It gets committed to many times per day by people who are only loosely aware of each others’ work. It has many dependencies including the compiler, operating system, and libraries, all of which are bugg
Efficient Integer Overflow Checking in LLVM – Embedded in Academia
(Here’s some optional background reading material.) We want fast integer overflow checking. Why? First, if the undefined behavior sanitizers go faster then testing goes faster. Second, when overhead drops below a certain point people will become willing to use UBSan to harden production code against integer overflows. This is already being done in parts of Android. It isn’t the kind of thing to do
Finding Compiler Bugs by Removing Dead Code – Embedded in Academia
I was pretty bummed to miss PLDI this year, it has been my favorite conference recently. One of the talks I was most interested in seeing was Compiler Validation via Equivalence Modulo Inputs by some folks at UC Davis. Although I had been aware of this paper (which I’ll call “the EMI paper” from now on) for a while, I was hesitant to write this post — the work is so close to my work that I can’t a
Heartbleed and Static Analysis – Embedded in Academia
Today in my Writing Solid Code class we went through some of the 151 defects that Coverity Scan reports for OpenSSL. I can’t link to these results but take my word for it that they are a pleasure to read — the interface clearly explains each flaw and the reasoning that leads up to it, even across multiple function calls. Some of the problems were slightly alarming but we didn’t see anything that l
Fastest FizzBuzz – Embedded in Academia
The always-entertaining FizzBuzz problem came up again on Hacker News today, and for no other reason than I just got out from under a nasty deadline, I looked around on the net for interesting solutions, for which this Rosetta Code page is a gold mine. The Windows batch file and BSD make versions are hilarious, though I was a bit disappointed that Piet was not represented. Anyhow, here it is: (ref
A Guide to Undefined Behavior in C and C++, Part 1 – Embedded in Academia
Also see Part 2 and Part 3. Programming languages typically make a distinction between normal program actions and erroneous actions. For Turing-complete languages we cannot reliably decide offline whether a program has the potential to execute an error; we have to just run it and see. In a safe programming language, errors are trapped as they happen. Java, for example, is largely safe via its exce
Embedded in Academia : A Quiz About Integers in C
The C language's rules for integer operations have some quirks that can make even small programs behave in confusing ways. This post is a review of these rules in the form of a quiz containing 20 questions. It is not intended to be extremely tricky, and I expect serious C programmers to get high scores. I recommend going through the questions in order. You should assume C99. Also assume that x86 o
1
リリース、障害情報などのサービスのお知らせ
最新の人気エントリーの配信
j次のブックマーク
k前のブックマーク
lあとで読む
eコメント一覧を開く
oページを開く
Formal-Methods-Based Bugfinding for LLVM’s AArch64 Backend – Embedded in Academia
Alive2 Part 1: Introduction – Embedded in Academia
Fun with Shellshock – Embedded in Academia
Early Superoptimizer Results – Embedded in Academia
Let’s Work on an LLVM Superoptimizer – Embedded in Academia
Safe, Efficient, and Portable Rotate in C/C++ – Embedded in Academia
A New Compiler Fuzzing Paper – Embedded in Academia