The Standup Memory Safe C
Nov 17, 2025
This week’s guests, Ed from LowLevel.Academy, a low-level security expert, and Casey Muratori, a game programmer, dive deep into memory-safe C. They discuss the innovative Fil-C technology, which blends memory safety with familiar C logic, making it suitable for game engines. Ed explains the security implications that sparked interest in memory-safe alternatives, while Casey shares practical insights on performance trade-offs. The duo also contrasts Fil-C with Rust, covering the strengths and limitations of each approach for modern programming.
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Fil‑C Adds Runtime Object Tracking
- Fil-C augments C with runtime pointer bounds and object tracking to prevent out-of-bounds and use-after-free exploits.
- It acts like a heavier, software-based version of hardware pointer tagging and enforces checks at runtime.
Plan For Noticeable Overhead
- Expect runtime overhead: measured slowdown ranges roughly 1.2x to 4x depending on workload.
- Plan for higher memory use and performance tradeoffs before adopting Fil‑C in production.
Sudo Rewrite Still Had Vulnerabilities
- Ed noted the sudo rewrite to Rust still produced CVEs, showing rewrites can introduce new vulnerabilities.
- He recommends instrumenting LLVM/IR checks as an alternative to full rewrites for safety.