On Windows, getcontext returns an error

[dinosaure]

It seems that getcontext returns a error and it's impossible for pth to spawn a new thread. Due to this error, a SEGFAULT is reached at one point where no threads was launched but pth_key_setdata expects a current one. I will try to find if the error come from Cosmopolitan or if it's a real barrier.

[dinosaure]

It seems not possible to use pth on Windows (it seems that only w32 is supported). More concretely, Cosmopolitan does not implement

• mcsc machine context method (makecontext(3)/setcontext(3)) for Windows (ESYS is returned)
• sas stack setup method (sigaltstack(2))
• ss stack setup method (sigstack(2))

sjljw32 is available but it works only for a 32-bits architecture which is too restrictive for us. We have 2 ways to solve this issue:

• implement required functions mcsc, sas or ss into Cosmopolitan
• modify pth to provide a Windows implementation of pth_mctx - we probably need to use the mcsc compilation path and check if we are into IsWindows() and do something else than makecontext/setcontext

[dinosaure]

The required interface of pth_mctx is:

typedef struct pth_mctx_t pth_mctx_t;

pth_mctx_switch(pth_mctx_t* , pth_mctx_t *);
pth_mctx_restore(pth_mctx_t *);
pth_mctx_set(pth_mctx_t *, void (*f)(void), char *addr_lo, char *addr_hi);

[dinosaure]

The best possibily is to integrate winpthreads into pth and use IsWindows() to switch from one implementation to another depending on the platform (thx @dra27 for his help). OCaml multicore will use it too so we ensure a certain coherence between Esperanto and OCaml Multicore.

[jart]

@dinosaure Cosmopolitan Libc has pthreads support now. https://github.com/jart/cosmopolitan/releases/tag/2.1 If there's an issue with setcontext() and getcontext() that are causing issues for fibers, then let me know and I'll fix it.

[dinosaure]

Thanks @jart, I will probably focus on that in 2~3 weeks 👍 - It's currently on top of my TODO list.

[jart]

Awesome to hear! Looking forward to seeing where it goes.

[dinosaure]

FIxed by #28 which uses Cosmopolitan 2.2 (which has pthread_ functions).