xtc_dump.h

/*-
 * Copyright (c) 2026, The XTC Project
 * Use of this source code is governed by the ISC License.
 *
 * src/inc/xtc_dump.h
 *      Crash diagnostics: a runtime-state dump (the programmatic form of
 *      the debugger's xtc-procs / xtc-loops / xtc-mailbox), plus panic and
 *      assert macros that emit it before aborting, and an optional fatal-
 *      signal handler that emits it on SIGSEGV / SIGBUS / SIGABRT.
 *
 *      xtc_dump writes, to a file descriptor:
 *        - the C backtrace of the CALLING (faulting) OS thread, when a
 *          backtrace backend is compiled in (see os_backtrace.h);
 *        - every scheduler loop with its run-queue / steal stats;
 *        - every live proc with its run state, park reason, and mailbox
 *          depth / peak / recv / drop counters.
 *      The field labels match the debugger scripts (tools/gdb,
 *      tools/lldb), so an in-process dump and a gdb session read alike.
 *
 *      A parked fiber's OWN C stack is NOT unwound: it lives in a saved
 *      coroutine context, not on a live OS thread.  Like an Erlang crash
 *      dump or a Go panic, the dump reports each proc's state and mailbox,
 *      not N reconstructed C stacks.  For deep per-fiber stacks attach a
 *      debugger to a core (the dump and the debugger share field names).
 *
 *      Signal-safety: xtc_dump takes the per-loop inspection locks (via
 *      xtc_inspect), so it is fully reliable from an explicit XTC_PANIC /
 *      XTC_ASSERT in normal context.  From the fatal-signal handler the
 *      backtrace (async-signal-safe) is always emitted; the proc/loop walk
 *      is attempted best-effort and may be skipped if a lock was held at
 *      the moment of the fault.  See docs/guide/debugging.md.
 */
 
#ifndef XTC_DUMP_H
#define XTC_DUMP_H
 
#include "xtc.h"
 
#if defined(__GNUC__) || defined(__clang__)
#  define XTC_NORETURN __attribute__((noreturn))
#else
#  define XTC_NORETURN
#endif
 
/*
 * PUBLIC: void xtc_dump __P((int));
 * PUBLIC: void xtc_panic __P((const char *, int, const char *, ...));
 * PUBLIC: int  xtc_crash_handler_install __P((void));
 */
 
/* Write a best-effort runtime-state dump to file descriptor `fd`
 * (commonly STDERR_FILENO).  Never allocates; safe to call at any
 * time.  Does not abort -- callers decide what to do next. */
void xtc_dump(int fd);
 
/* Emit `fmt`/... as a panic banner, then xtc_dump(STDERR_FILENO), then
 * abort().  Use the XTC_PANIC macro rather than calling directly. */
void xtc_panic(const char *file, int line, const char *fmt, ...) XTC_NORETURN;
 
/* Install a fatal-signal handler (SIGSEGV, SIGBUS, SIGABRT, SIGFPE,
 * SIGILL) that emits a backtrace + best-effort runtime dump to stderr,
 * then re-raises the signal with the default disposition (so a core is
 * still produced).  Returns XTC_OK, or XTC_E_NOSYS where unsupported.
 * Idempotent.  Does NOT install SIGCHLD/SIGTERM/etc. -- only faults. */
int xtc_crash_handler_install(void);
 
/* Log `fmt`/..., dump runtime state, and abort. */
#define XTC_PANIC(...) xtc_panic(__FILE__, __LINE__, __VA_ARGS__)
 
/* Abort with a dump unless `cond` holds. */
#define XTC_ASSERT(cond) \
        do { if (!(cond)) \
                xtc_panic(__FILE__, __LINE__, "assertion failed: %s", #cond); \
        } while (0)
 
/* Like XTC_ASSERT but with a custom printf-style message. */
#define XTC_ASSERT_F(cond, ...) \
        do { if (!(cond)) xtc_panic(__FILE__, __LINE__, __VA_ARGS__); } while (0)
 
#endif /* XTC_DUMP_H */