Fil-C: A memory-safe C implementation

6 months ago

Fil-C is a memory-safe implementation of C and C++ that allows existing C code to run safely without modification.
It is fanatically compatible with existing C code, making it suitable for retrofitting memory safety into legacy applications.
Fil-C can compile an entire memory-safe Linux user space, though some complex programs require modifications.
The project is a fork of Clang, licensed under Apache v2.0 with LLVM exceptions, and is currently based on Clang version 20.1.8.
Performance has improved from initial slow speeds to being only a few times slower than Clang, depending on the program structure.
Fil-C uses a different internal ABI than Clang, requiring all code to be recompiled with Fil-C for compatibility.
The InvisiCaps pointer representation ensures memory safety while maintaining the appearance of natural pointer sizes for the architecture.
Memory management includes a concurrent garbage collector that is both parallel and precise, using auxiliary capability information.
Fil-C has been used to create a memory-safe Linux user space based on Linux From Scratch, though some components still require a non-Fil-C compiler.
Despite its immaturity, Fil-C offers a compelling solution for memory safety in C programs, especially where performance trade-offs are acceptable.

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