main-func: add DEFINE_MAIN_FUNCTION_FIBER
Provide a Tokio-like #[tokio::main] entry point for binaries that want to run their main function inside a fiber on a default sd_event loop. DEFINE_MAIN_FUNCTION_FIBER(impl) mirrors DEFINE_MAIN_FUNCTION but routes impl through a new run_main_fiber() helper. impl keeps the run() convention while the loop's exit code keeps the exit status convention: impl's result never becomes an exit code, an explicit exit status wins over a successful impl, and impl's own failure wins over the exit status unless it is the -ECANCELED of a fiber that the exit request cancelled. Signal policy stays with impl so existing handlers such as sd_event_set_signal_exit() keep working. The fiber is created fire-and-forget: as long as the loop reaches SD_EVENT_FINISHED it unwinds the fiber through its exit event source, so we never hold a reference we cannot drop because the fiber is still suspended. A loop that fails internally never dispatches its exit sources, so the fiber may stay suspended with no working loop left to unwind it; we leak both for now and leave a TODO to keep the broken loop out of the default slot. Since the fiber also refers to run_main_fiber()'s stack frame, refuse to run on a loop we don't own, or from a fiber, as sd_fiber_new() leaves the exit event source disabled there and nothing would unwind the fiber. Cover argument forwarding, result propagation, explicit event exits, nested invocations, signal-source registration, event-loop errors, and fiber stack unwinding, and check after every run that the default event loop was released again. Also build and run a separate test executable that expands DEFINE_MAIN_FUNCTION_FIBER itself and verifies that a positive implementation result maps to a successful process exit.
This commit is contained in:
Daan De Meyer
@@ -147,6 +147,8 @@ simple_tests += files(
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'test-login-util.c',
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'test-machine-util.c',
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'test-macro.c',
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'test-main-func-fiber.c',
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'test-main-func.c',
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'test-memfd-util.c',
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'test-memory-util.c',
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'test-mempool.c',
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@@ -0,0 +1,16 @@
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include "main-func.h"
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#include "tests.h"
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static int run(int argc, char *argv[]) {
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ASSERT_GE(argc, 1);
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ASSERT_NOT_NULL(argv);
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ASSERT_NOT_NULL(argv[0]);
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ASSERT_NULL(argv[argc]);
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/* A positive result means success, so this has to exit zero. */
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return 23;
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}
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DEFINE_MAIN_FUNCTION_FIBER(run);
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@@ -0,0 +1,148 @@
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <signal.h>
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#include "sd-event.h"
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#include "sd-future.h"
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#include "main-func.h"
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#include "tests.h"
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static char *test_argv[] = {
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(char*) "alpha",
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(char*) "beta",
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NULL,
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};
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static void assert_test_argv(int argc, char *argv[]) {
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ASSERT_EQ(argc, 2);
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ASSERT_PTR_EQ(argv, test_argv);
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ASSERT_STREQ(argv[0], "alpha");
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ASSERT_STREQ(argv[1], "beta");
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ASSERT_NULL(argv[2]);
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}
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static int run_main_fiber_checked(main_fiber_func_t func) {
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_cleanup_(sd_event_unrefp) sd_event *event = NULL;
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int r;
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r = run_main_fiber(2, test_argv, func);
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/* The main fiber, and with it the event loop it pins, has to be gone by the time run_main_fiber()
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* returns, so allocating the default event again must hand out a fresh one. */
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ASSERT_OK_POSITIVE(sd_event_default(&event));
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return r;
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}
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static int return_argc(int argc, char *argv[]) {
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assert_test_argv(argc, argv);
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return argc;
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}
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static int return_cancelled(int argc, char *argv[]) {
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assert_test_argv(argc, argv);
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return -ECANCELED;
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}
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TEST(result) {
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/* Positive results mean success and stay out of the exit status. */
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ASSERT_OK_ZERO(run_main_fiber_checked(return_argc));
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ASSERT_ERROR(run_main_fiber_checked(return_cancelled), ECANCELED);
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}
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static int nested_run(int argc, char *argv[]) {
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assert_test_argv(argc, argv);
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/* Attaching another main fiber to the running loop would leave it behind once we return. */
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ASSERT_ERROR(run_main_fiber(argc, argv, return_argc), EBUSY);
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return 0;
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}
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TEST(nested) {
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ASSERT_OK_ZERO(run_main_fiber_checked(nested_run));
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}
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static int signal_to_raise;
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static int raise_signal(int argc, char *argv[]) {
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assert_test_argv(argc, argv);
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ASSERT_OK(sd_event_set_signal_exit(sd_fiber_get_event(), true));
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ASSERT_OK_ERRNO(raise(signal_to_raise));
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ASSERT_ERROR(sd_fiber_suspend(), ECANCELED);
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return -ECANCELED;
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}
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TEST(signal) {
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FOREACH_ARGUMENT(signal_to_raise, SIGINT, SIGTERM)
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ASSERT_OK_ZERO(run_main_fiber_checked(raise_signal));
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}
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static int fail_event(sd_event_source *s, void *userdata) {
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ASSERT_NOT_NULL(s);
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ASSERT_NULL(userdata);
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return -EINVAL;
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}
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static bool fiber_unwound;
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static void mark_fiber_unwound(bool *marker) {
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ASSERT_NOT_NULL(marker);
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fiber_unwound = true;
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}
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static int event_loop_error(int argc, char *argv[]) {
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_cleanup_(sd_event_source_unrefp) sd_event_source *defer = NULL;
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_unused_ _cleanup_(mark_fiber_unwound) bool unwind_marker = false;
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assert_test_argv(argc, argv);
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ASSERT_OK(sd_event_add_defer(sd_fiber_get_event(), &defer, fail_event, /* userdata= */ NULL));
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ASSERT_OK(sd_event_source_set_exit_on_failure(defer, true));
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ASSERT_ERROR(sd_fiber_suspend(), ECANCELED);
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return -ECANCELED;
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}
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TEST(event_loop_error) {
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fiber_unwound = false;
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ASSERT_ERROR(run_main_fiber_checked(event_loop_error), EINVAL);
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ASSERT_TRUE(fiber_unwound);
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}
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static int exit_event(int argc, char *argv[]) {
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assert_test_argv(argc, argv);
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ASSERT_OK(sd_event_exit(sd_fiber_get_event(), 23));
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ASSERT_ERROR(sd_fiber_suspend(), ECANCELED);
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return -ECANCELED;
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}
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static int exit_event_and_return(int argc, char *argv[]) {
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assert_test_argv(argc, argv);
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ASSERT_OK(sd_event_exit(sd_fiber_get_event(), 23));
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return 0;
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}
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static int exit_event_and_fail(int argc, char *argv[]) {
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assert_test_argv(argc, argv);
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ASSERT_OK(sd_event_exit(sd_fiber_get_event(), 0));
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return -ENOANO;
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}
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TEST(event_exit_code) {
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ASSERT_EQ(run_main_fiber_checked(exit_event), 23);
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ASSERT_EQ(run_main_fiber_checked(exit_event_and_return), 23);
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/* Requesting an exit doesn't cancel a running impl, so its failure still wins. */
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ASSERT_ERROR(run_main_fiber_checked(exit_event_and_fail), ENOANO);
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}
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DEFINE_TEST_MAIN(LOG_DEBUG);
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