2026-08-11: Cleaning costs, or, examining the OpenBSD -fret-clean flag
Examining whether an OpenBSD compiler-based anti-ROP mitigation is worth it
Dr. Brian Robert Callahan
academic, developer, with an eye towards a brighter techno-social life
Latest posts
2026-07-13: I bootstrapped GDC with DMD
"Correcting" some GCC documentation
2026-06-09: An addendum I really didn't want to write
So I didn't
2026-03-22: Semi-retirement, or, really, changing my relationship with the BSDs
Evaluating some OpenBSD security measures
2025-12-16: Let's run FreeBSD 15.0-RELEASE on a Raspberry Pi Zero 2 W
Instructions to get a small embedded ARM64 device working with the latest FreeBSD operating system
2025-09-01: Let's write a peephole optimizer for QBE's arm64 backend
Learn how to cross-compile a native GCC toolchain
2025-08-17: Despite thoughts to the contrary, GNAT (Ada) is in fact fully supported on illumos
Learn how to cross-compile a native GCC toolchain
2025-08-13: The GNU D compiler has been broken on FreeBSD 14 for over a year and no one noticed, or, why operating system package maintainers matter
Discovery and diagnosis of a bug hiding in plain sight
2025-05-16: I revived pkgsrc on AIX
Step-by-step process to get pkgsrc working on modern AIX
2025-03-29: GCC 14.2.0 on PowerPC Mac OS X 10.4 Tiger
Step-by-step process to get a modern GCC on an old Mac OS X
2025-02-22: State of virtualizing the BSDs on Apple Silicon
Testing VMWare Fusion and the Apple virtualization framework with each *BSD
2025-01-12: Let's port the GNAT Ada compiler to macOS/aarch64
Getting a compiler written in its own langauge bootstrapped for a new platform
2024-12-16: Let's cross compile from FreeBSD/amd64 to macOS/aarch64
A quick tutorial for setting up a complete cross compiling envinroment using a FreeBSD/amd64 host and macOS/aarch64 target
2024-12-12: A GDC package for macOS/aarch64
A walkthrough to bootstrap GDC on macOS/aarch64
2024-06-09: A DMD package for OpenIndiana
A walkthrough to bootstrap DMD on OpenIndiana
2024-03-06: FreeBSD has a(nother) new C compiler: Intel oneAPI DPC++/C++
A walkthrough to get Intel oneAPI DPC++/C++ to output native binaries for FreeBSD
2024-01-22: Can GCC use Clang as its assembler?
How to use LLVM as the assembler for GCC, for FreeBSD and other systems
2024-01-01: FreeBSD has a new C compiler: Oracle Developer Studio 12.6
A walkthrough to get Oracle Developer Studio 12.6 to output native binaries for FreeBSD
2023-11-19: Enabling LLVM with m68k (and more) support on OpenBSD
Adding the experimental LLVM targets to the OpenBSD LLVM packages
2023-08-13: Can mold be used as the OpenBSD system linker?
My ordeal trying to get mold to be /usr/bin/ld on OpenBSD
2023-07-23: Using non-GNU assemblers with the Portable C Compiler
Can the Sun assembler and Yasm be used with PCC?
2023-07-05: Porting the Portable C Compiler (PCC) to Illumos
Teaching an old compiler new tricks.
2023-07-03: Installing Oracle Developer Studio 12.6 on Illumos
The (mis)adventures of installing Developer Studio on Illumos despite Oracle's many attempts to stop me.
2023-06-26: GCC --enable-languages=all on OpenBSD
Can we build all ten GCC langauge frontends on OpenBSD?
2022-12-19: GCC now includes Modula-2 and Rust. Do they work on OpenBSD?
Reviewing the state of the new Modula-2 and Rust frontends for GCC on OpenBSD.
2022-11-13: I took the CompTIA CySA+ CS1-003 beta exam for fun
Reflections on the new CySA+ exam I took today.
2022-07-04: Your next C compiler is a D compiler: Introducing DMD's ImportC
Demonstrating the C compiler that lives inside a D compiler.
2022-06-29: OpenBSD has two new C compilers: chibicc and kefir
Discussing porting chibicc and kefir to OpenBSD.
2022-04-27: I ported the new Hare compiler to OpenBSD
A walkthrough on porting a brand new language to OpenBSD.
2022-04-26: Let's try V on OpenBSD
My thoughts on trying out the V programming language and its first-party apps for the first time.
2022-04-18: Let's install OpenBSD/riscv64 on QEMU
Step-by-step instructions to get OpenBSD/riscv64 running on QEMU.
2022-04-17: I wrote a peephole optimizer (for QBE), part 3: Studying the LLVM and GCC optimizers
We study how LLVM and GCC optimize increments and decrements and teach those optimizations to our QBE optimizer.
2022-04-06: Hand-optimizing the TCC code generator
Let's teach the Tiny C Compiler to emit better code.
2022-04-02: I wrote a simple, explainable, peephole optimizer (for cproc and QBE), part 2
Finishing up our peephole optimizer from the previous blog post.
2022-03-30: I wrote a peephole optimizer (for QBE), part 1
Introducing O, a peephole optimizer to fix up missed opportunities in QBE.
2022-03-21: I built the new gcobol compiler on OpenBSD
Trying out the new GCC COBOL frontend on OpenBSD.
2022-02-22: I took the CompTIA Linux+ XK1-005 beta exam for fun
Reflections on the new Linux+ exam I took last week.
2022-02-20: I wrote the least-C C program I could
Abusing the C preprocessor for fun and profit.
2022-02-05: I took the CompTIA Project+ PK1-005 beta exam for fun
Reflections on the new Project+ exam I took today.
2021-12-04: Supporting a new C compiler for oksh and review of the vbcc C compiler
Learning how to get the vbcc C compiler up and runnin on OpenBSD and able to compile the oksh shell.
2021-10-31: More OpenBSD and D news
Quick post to keep everyone updated on the latest OpenBSD and D news from me.
2021-10-20: An LDC bootstrap compiler and LDC package for OpenBSD
A short post writing down how to create a bootstrap LDC compiler for the OpenBSD port.
2021-10-13: Packaging the DMD D compiler for OpenBSD
Previewing my DConf 2021 talk about D on OpenBSD by discussing how the new DMD package came to be.
2021-10-10: Benchmarking the oksh shell, or, let's look at a lot of C compilers
Getting inconclusive numbers about the definitively best Unix shell.
2021-09-11: I got the J language working on OpenBSD
A detailed write-up on porting J to OpenBSD.
2021-09-06: Let's write a self-hosting compiler, part 1: Reading in source code
Beginning a new compiler-writing adventure in which we will produce a self-hosting PL/0 compiler.
2021-08-29: Let's get hands-on with QBE
Learning the QBE Intermediate Language via writing a small Brainfuck compiler directly in QBE IR.
2021-08-26: Let's write a compiler, part 8: Strings, forward references, and conclusion
Adding the last few pieces needed for a finished PL/0 compiler.
2021-08-22: Let's write a compiler, part 7: Arrays
Adding array support to our PL/0 compiler.
2021-08-19: Let's write a compiler, part 6: Input and output
Adding basic input and output routines to our PL/0 compiler.