I Made a Realtime C/C++ Build Visualizer

Summary

Many software projects take a long time to compile. Sometimes that’s just due to the sheer amount of code, like in the LLVM project. But often a build is slower than it should be for dumb, fixable reasons.I’ve had the suspicion that most builds are doing dumb stuff, but I had no way to see it. So I’ve been working on a cross-platform tool to help speed up builds (you can try it, see below). It works with any build system or programming language (Not just C/C++). Its timeline looks like this:It’s more than just a generic system profiler: it looks for build-specific problems. A few examples: using make without the -j flag, disproportionate time being spent on certain files or compiler phases (as reported by tools like clang’s -ftime-trace), and commands that could’ve been run in parallel but weren’t. It’s especially helpful for optimizing CI builds, which are often clean rebuilds without caching.I named it What the Fork after the fork() system call that spawns new processes. You use it by writing wtf before a build command:$ # A few possible examples: $ wtf make $ wtf cargo build $ wtf gradle build $ wtf npm run build $ wtf zig build $ wtf -x # starts a build of the front most Xcode window Here it is recording the build of a macOS app: Your browser does not support the video tag.How it worksA build is just a bunch of commands that produce your finished program. At its simplest, it could be a shell script like this:#!/bin/bash clang main.c -o program That script requires 3 programs to produce the final result: bash, clang, and — surprise! — ld, the linker, which clang runs automatically. Unexpected build steps are often the source of slowdowns and are even more likely in bigger projects, which often use something like cargo, make, bazel, gradle, or xcodebuild instead of a shell script. Those tools still just execute commands, but they also perform caching, dependency analysis, and scheduling to do the least amount of work as efficiently as possible.While you can see th...