Jan Korous
Security Tools Engineer at Apple
San Francisco Bay Area United States
Summary
🤩
Rockstar🎓
Top SchoolJan Korous is a Security Tools Engineer in the San Francisco Bay Area with eight years of experience building compiler-based security and tooling at Apple. He specializes in Clang/LLVM internals, static analysis, and automated approaches to make large C++ codebases bounds-safe, having led teams and projects that harden compile-time behavior. His open-source contributions to clang, clang-tools-extra (clangd) and swift-clang demonstrate deep expertise in USR mangling, indexing, JSON-RPC handling and robustness fixes that improve language tooling at the compiler level. Jan pairs systems-level compiler work with practical security tooling—bridging low-level diagnostics and large-scale automated remediation. Trained in computational and applied mathematics and physics, he brings a rigorous, bug-forensics mindset to subtle type- and parsing-related failures. Colleagues rely on him for hard-to-reproduce fixes that improve both developer experience and production safety.
8 years of coding experience
10 years of employment as a software developer
Computational and Applied Mathematics, Computational and Applied Mathematics at Charles University in Prague
Czech, English, German
Github Skills (13)
json-rpc10
parserator10
compiler10
c-language10
compiler-compiler10
parser10
clangd10
cprogramming-language10
indexing10
clang10
llvm10
indexof9
template-metaprogramming9
Programming languages (4)
Github contributions (5)
apple/swift-clang
Oct 2017 - Oct 2019
Role in this project:
Back-end Developer & Compiler Engineer
Back-end Developer & Compiler EngineerContributions:92 commits, 17 PRs, 43 pushes in 2 years
Contributions summary:Jan primarily focused on improving the clang compiler. They implemented fixes for USR mangling in the indexer for various C++ constructs, including fixed-size arrays, function pointer types, and default template template parameter values. The user also addressed a crash related to type-dependent base classes and improved diagnostics for type-related errors in the parser. These contributions directly enhance the compiler's ability to correctly handle C++ code.
llvm-mirror/clang-tools-extra
Mar 2018 - Oct 2019
Mirror kept for legacy. Moved to https://github.com/llvm/llvm-project
Role in this project:Back-end Developer
Back-end DeveloperContributions:22 commits in 1 year 7 months
Contributions summary:Jan primarily contributed to the clangd component of the repository. Their commits focused on improving the clangd functionality, specifically related to the indexing and JSON-RPC dispatching. The contributions include fixing undefined behavior, handling of EOF in delimited input, and improving delimiter handling, ensuring the robustness of the clangd service. They also made changes related to the SymbolID and SymbolInfo features.
llvmstatic-analysisrefactoringreformat
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