Geert Custers
Co-Founder at Rogue IT Consulting
Delft, South Holland, Netherlands
Summary
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Rockstar🎓
Top SchoolGeert Custers is a systems-focused software engineer and co-founder with 11 years of experience building low-level, high-performance software and hardware-aware systems. Currently at Hadrian and co-founding Rogue IT Consulting, he contributes to microkernel OS work and a portable C standard library—adding POSIX/Linux syscall support, ACPI integration, block device arbitration and richer procfs entries. His background spans research (distributed dynamic graph algorithms implemented in C++ with published papers) and industry internships at ASML and TNO, reflecting a blend of academic rigor and practical engineering. Perpetually curious about systems programming, HPC and computer engineering, he often surfaces non-obvious value by improving build/testing infrastructure and integrating dynamic linkers into static builds to make foundational components more complete and usable.
11 years of coding experience
High School Diploma, High School Diploma at International School HilversumMaster's degree Computer Engineering, Master's degree Computer Engineering at Delft University of Technology
Dutch, English, German
Stackoverflow
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Github Skills (32)
c-language10
posixct10
os-development10
c-programming10
linux-kernel10
microkernel10
system-calls10
api10
posix10
fileio10
file-handling10
file-processing10
file-access10
cprogramming-language10
operating-system10
Programming languages (10)
Github contributions (5)
managarm/mlibc
Jan 2019 - Nov 2022
Portable C standard library
Role in this project:
Back-end Developer & System Engineer
Back-end Developer & System EngineerContributions:583 reviews, 392 commits, 332 PRs in 3 years 10 months
Contributions summary:Geert primarily contributed to the mlibc project by implementing and extending system call support within the library, focusing on POSIX and Linux compatibility. Their work included adding new system call stubs and implementations, such as those related to terminal control (tcsetattr, tcgetattr), time management (clock_gettime, getrusage), and file I/O (open_memstream). Furthermore, the user was involved in refactoring the build and testing infrastructure, with the aim of integrating a dynamic linker into the static build process, creating a more complete standard C library.
cppc-librarystandard-libraryportablex86-64
managarm/managarm
May 2021 - Dec 2021
Pragmatic microkernel-based OS with fully asynchronous I/O
Role in this project:Back-end Developer
Back-end DeveloperContributions:30 reviews, 11 commits, 7 PRs in 7 months
Contributions summary:Geert contributed to the development of the microkernel-based operating system, focusing on core system functionalities. Their work includes adding stack trace functionality for debugging, integrating ACPI support for hardware initialization, and implementing block device arbitration within the POSIX layer. They also added raw device access and enhanced the procfs with /proc/*/exe and /proc/*/maps entries. Further contributions involved adding a kernel frame pointers.
microkernelkernelasynchronousoperating-systemlinux
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