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Fil-C 0.667

![Screenshot_20241126_085419_Chrome.jpg](great thing)

This is a spare-time personal project that I'm doing for fun. It's called Fil-C.

What is it? It's a totally memory-safe version of C and C++. All memory safety errors are caught as Fil-C panics. Fil-C achieves this using a combination of real-time garbage collection and invisible capabilities (each pointer in memory has a corresponding capability, not visible to the C address space). Every fundamental C operation (as seen in LLVM IR) is checked against the capability. Fil-C has no unsafe escape hatch of any kind.

Requirements

Fil-C only works on Linux/X86_64.

Previous versions worked on Darwin/ARM64 and FreeBSD, but now I'm focusing just on Linux/X86_64 because it allows me to do a more faithful job of implementing libc. There's nothing fundamentally stopping Fil-C from working on ARM or OSes other than Linux.

Getting Started

If you downloaded Fil-C binaries, run:

./setup.sh

If you downloaded Fil-C source, run:

./setup_gits.sh
./build_all.sh

Then you'll be able to use Fil-C from within this directory. There is no way to "install" it, because that would be a crazy thing to do for such an experimental piece of software!

Things That Work

Included in the binary distribution (or if you build from source using build_all.sh) is:

  • Memory-safe SSH client and server.

  • Memory-safe curl.

  • Memory-safe libz and openssl.

  • Memory-safe libc (based on musl) and libc++ (based on LLVM's libc++).

  • A version of clang that you can use to compile C or C++ programs.

Fil-C catches all of the stuff that makes memory safety in C hard, like:

  • Out-of-bounds on the heap or stack.

  • Use-after free (also heap or stack).

  • Type confusion between pointers and non-pointers.

  • Type errors arising from linking.

  • Type errors arising from misuse of va_lists.

  • Pointer races.

  • System calls. All buffers passed to system calls are checked for bounds and type.

  • Lots of other stuff.

Fil-C comes with a reasonably complete POSIX libc and even supports tricky features like threads, signal handling, mmap/munmap, longjmp/setjmp, and C++ exceptions.

Things That Don't Work

Fil-C is not a complete product. Lots of stuff isn't done!

  • Fil-C doesn't do anything about UB not related to memory, yet. For example, dividing by zero may take the compiler down a weird path.

  • I'm still working on performance. In good cases, it's 1.5x slower than normal C. In bad cases, it's 5x slower. Lots of work remains to fix those bad cases.

  • Probably other stuff, too!

These are all things that can be fixed. They just haven't been, yet.

Learn More

The best write-up of Fil-C is the manifesto.

You can also e-mail me: [email protected]

And follow my rants on Twitter.

I don't have a bug database or anything like that, so bothering me on Twitter or over e-mail is your best bet, probably. And I might ignore you anyway.

No guarantees!