coro_int.h

/*-
 * Copyright (c) 2026, The XTC Project
 * Use of this source code is governed by the ISC License.
 *
 * src/inc/coro_int.h
 *      Internal types for the L2 coroutine substrate.
 */
 
#ifndef XTC_CORO_INT_H
#define XTC_CORO_INT_H
 
#if defined(_WIN32)
# include <windows.h>
#elif defined(XTC_HAVE_UCONTEXT) && !defined(XTC_CORO_FORCE_FCTX)
# include <ucontext.h>
#endif
 
#include "xtc_async.h"
#include "loop_int.h"
 
/*
 * The fiber context attached to an xtc_task_t when it was spawned
 * via xtc_async.  Lives in the per-task arena (currently malloc).
 */
struct xtc_coro {
#if defined(_WIN32)
        LPVOID       fiber;         /* the coroutine's own Win32 fiber */
        LPVOID       loop_fiber;    /* return-to-loop fiber pointer */
#elif defined(XTC_HAVE_UCONTEXT) && !defined(XTC_CORO_FORCE_FCTX)
        ucontext_t   ctx;          /* the coroutine's own machine state */
        ucontext_t   loop_ctx;     /* return-to-loop context (set on resume) */
#else
        /* fcontext substrate (coro_fctx.c): a single saved stack pointer.
         * On make_fcontext it is the fresh entry point; each yield/await
         * overwrites it with the coroutine's current resume point.  The
         * scheduler's return point is a per-thread cursor in coro_fctx.c,
         * not stored here, because coroutines always return to the
         * scheduler, never directly to one another. */
        void        *fctx;
#endif
        void        *stack;
        size_t       stack_sz;
        xtc_coro_fn  fn;
        void        *arg;
        intptr_t     result;
        int          done;          /* 1 once fn has returned */
 
        xtc_task_t  *self;          /* back-pointer to our task */
        xtc_task_t  *waiter;        /* task awaiting this one (or NULL) */
 
        /*
         * When non-NULL, this coroutine has just registered itself as
         * the `waiter` of another and is yielding into the loop with
         * the intent of staying parked rather than rescheduling.  The
         * step function reads and clears this flag to decide between
         * RESCHED and PENDING.
         */
        struct xtc_coro *_parked_on;
 
        /*
         * Sanitizer fiber-switch save token (ASan/TSan/LSan).  Holds this
         * coro's "fake stack" across a park so __sanitizer_start/finish_
         * switch_fiber can track the user-space stack switch and stop
         * mis-attributing stack memory.  Unused (always NULL) in a
         * non-sanitized build.  See XTC_FIBER_SWITCH_ANNOTATE in
         * coro_fctx.c / coro_uctx.c.
         */
        void        *san_fake_stack;
 
        /*
         * TSan fiber-IDENTITY token (clang ThreadSanitizer only).  TSan
         * does NOT implement __sanitizer_*_switch_fiber; it needs each
         * coroutine represented as a TSan "fiber object" (__tsan_create_
         * fiber at create, __tsan_switch_to_fiber at every switch,
         * __tsan_destroy_fiber at teardown) so it can carry per-fiber
         * happens-before across cooperative switches instead of seeing
         * them as one confused thread.  Distinct from san_fake_stack (the
         * two sanitizer models are mutually exclusive per build).  Always
         * NULL unless built with clang -fsanitize=thread.  See
         * XTC_TSAN_FIBERS in coro_fctx.c / coro_uctx.c.
         */
        void        *tsan_fiber;
};
 
/* Shared by loop.c -- the currently-running coroutine on this loop.  */
extern XTC_THREAD_LOCAL struct xtc_coro *__xtc_current_coro;
 
/* Forward declarations for the dispatch glue.  */
int  __xtc_coro_step(xtc_task_t *self, void *user);
 
/* The task wrapping the currently-running coroutine on this thread,
 * or NULL when not running inside a coroutine.  Lets lower-level
 * primitives (e.g. xtc_amutex) find the current task to park it. */
xtc_task_t *__xtc_current_task(void);
 
#endif /* XTC_CORO_INT_H */