Comment by matheusmoreira
5 years ago
I remember simple use cases for clone() such as spawning child processes with just enough shared resources to execve(). I remember reading a lot of old emails from Torvalds about it, can't find them anymore.
I used to value portability but now I believe in using Linux everywhere and for everything. I like OpenBSD too but Linux is the stable one you can build anything on. What I wanted to eventually accomplish is a 100% freestanding Linux user space with no libraries at all. Maybe boot straight into the program I want to use, just like we can pass init=/usr/bin/bash in the kernel command line. How far could this go? Using nothing but system calls it's actually possible to get a framebuffer and use software renderering to draw some graphics. I'm guessing pretty far.
By starting from scratch like this it's possible to fix all the historical problems with our systems. For example, I think it's unacceptable when libraries keep global state. This can't be fixed without getting rid of libc and its buffers and caches and errno. Removing this cruft would actually simplify a threads implementation. And then there's completely insane stuff like .init and .fini sections:
https://blogs.oracle.com/solaris/init-and-fini-processing-wh...
A similar statically-linked user space project I found years ago:
That seems kind of contradictory. Your biases are tuned towards what works for big codebases but you're taking a first principles approach. A simplified threads implementation is called Java. Plus it gives you cool classes like Phaser. Threads will always be a horror show with C/C++. There's a reason why Linux is the only kernel that implements clone(). It's controversial.