[kees99]

Claude has surprisingly good knowledge of X11 protocol.

The other day, colleague showed me a (pretty basic) terminal emulator written in one-shot by Opus. Kicker is - that was compiled to a 30 KB static binary. That's right. No libX11, no libXfont, not even libc.

[amszmidt]

Only because the X Window System is very heavily documented, e.g., in the excellent "The Definitive Guides to the X Window System Series".

[vidarh]

Yeah, I've had it work on an X11 server using a Ruby X11 protocol implementation instead of libX11, and it just rushed ahead and added support for a bunch of missing requests and responses. None of that is hard - it's all very well documented - but it's tedious.

My terminal emulator using the same binding also started out hand-written but Claude overhauled that too recently and it knows vtxx escape codes far better than me too.

[JCattheATM]

You wrote your own terminal emulator?

[glitchc]

No libc? It used inline assembly routines?

[kees99]

Yes, something like this:

  static inline long read(int fd, void *buf, long count) {
    register long rax asm("rax") = __NR_read;
    register long rdi asm("rdi") = (long)fd;
    register long rsi asm("rsi") = (long)buf;
    register long rdx asm("rdx") = count;

    asm volatile(
        "syscall"
        : "+r"(rax)
        : "r"(rdi), "r"(rsi), "r"(rdx)
        : "rcx", "r11", "memory"
    );
    return rax;
  }

[asveikau]

The linux kernel also has its own headers (IIRC it was something like <asm/unistd.h> and/or <sys/syscall.h>, but might depend on architecture and version) where it will provide the stub asm statements.

In my memory the syscall ABI has changed a few times (i386 had int $0x80, then sysenter, then abstracting it in the vdso, then amd64 has 'syscall'), so it may be easier to let the kernel header provide the mechanism.

[yjftsjthsd-h]

The Linux syscall ABI is (famously) stable; on x86* you can still call into 0x80 just fine. There might be new interfaces made available, but existing programs shouldn't break. Although, in C there could be value in abstracting over the per-platform differences like int/syscall. I've only ever done raw syscalls from assembly where portability was rather moot:)

[Chu4eeno]

It's quite easy to get it to do syscalls directly, I even got Fable to do a simple standalone TLS implementation (in C). Not really useful since it hardcoded a set of supported algorithms etc., but it's fun to see how "simple" you can force it to go.