James Mcnellis
Principal Software Engineer, Game Engine Security at Roblox
Washington, District of Columbia, United States
Summary
🤩
Rockstar🎓
Top SchoolJames Mcnellis is a Principal Software Engineer with 14 years of systems-level experience building compilers, debuggers, and high-performance runtime systems for Windows and game engines. He led architecture for Time Travel Debugging replay and shipped ARM Pointer Authentication-based control-flow integrity across Windows, and later contributed core language and JIT work for Luau at Roblox. Known for deep C++ expertise and systems programming craftsmanship, he blends security-first design with practical engineering to make tools dramatically faster and more scalable. Based in Washington, D.C., he pairs technical leadership with a curiosity beyond code—classical music, photography, and a taste for scotch—which often surfaces in thoughtful, conference-grade presentations and mentorship.
14 years of coding experience
14 years of employment as a software developer
Master of Science Computer Science / Artificial Intelligence, Master of Science Computer Science / Artificial Intelligence at The University of Texas at ArlingtonBachelor of Arts Philosophy, Bachelor of Arts Philosophy at The Catholic University of America
c++, c
Stackoverflow
351,412reputation
27.7mreached
2,714answers
14questions
constants
top-1%
closures
top-5%
floating-point
top-5%
debugging
top-5%
malloc
top-5%
grammar
top-5%
Github Skills (131)
multithreading10
multidimensional-arrays10
windows10
c-preprocessor10
operator-overloading10
winapi10
gcc10
printf10
if-statement10
lua10
scripting-language10
casting10
visual-studio10
compiler-construction10
overriding10
Programming languages (4)
Github contributions (5)
dbremner/cxxreflect
Oct 2011 - May 2012
Contributions:39 commits in 6 months
microsoft/STL
Oct 2022 - Jul 2025
MSVC's implementation of the C++ Standard Library.
Contributions:1 review in 2 years 9 months
cpp
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