feat(scheduler-sim-decision-trace): pass the scheduler log path to the simulation driver

Task 4.4: the --logfile path (or the default, now SCHED_DEFAULT_LOG_PATH)
reaches the sim driver as an owned copy so the trace file checks can
reject the scheduler log.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/scheduler/include/sim.h

@@ -101,8 +101,22 @@ typedef struct {
      * style direct core init, matching sched_sim_driver_start()'s own
      * memset(sim, 0, sizeof(*sim)) default. */
     bool                    allocator_thread_live;
+    /* scheduler-sim-decision-trace task 4.4 (Req 8.3): the scheduler log
+     * file this process writes to (--logfile, else SCHED_DEFAULT_LOG_PATH).
+     * An owned copy made by sched_sim_driver_start() and freed by
+     * sched_sim_driver_fini(); the REPL's trace-file checks reject a trace
+     * file that is the same file (dev/inode) as this one. */
+    char*                   log_path;
 } xce_sched_sim_driver_t;
 
+/*
+ * SCHED_DEFAULT_LOG_PATH - the scheduler log file main.c uses when --logfile
+ * is not given. sched_sim_driver_start() falls back to the same path when
+ * `sched_sim_args_t.log_path` is NULL, so the driver always names the file
+ * the scheduler actually logs to.
+ */
+#define SCHED_DEFAULT_LOG_PATH "/tmp/xce_scheduler.log"
+
 /*
  * SCHED_SIM_START_TS_LATEST - default value for `sched_sim_args_t.sim_start_ts`
  * when the caller does not pass --sim-start-ts (main.c). AC 13's own
@@ -148,6 +162,8 @@ typedef struct {
         alt_events_path;      /* --sim-alt-events FILE (optional, task 11.5) */
     const char* output_path;  /* --sim-output FILE (optional, task 11.5) */
     bool        interactive;  /* --interactive / -i (task 12) */
+    const char* log_path;     /* --logfile FILE (optional; NULL means
+                               * SCHED_DEFAULT_LOG_PATH) */
 } sched_sim_args_t;
 
 /*

src/scheduler/src/main.c

@@ -225,7 +225,7 @@ static void sig_handler(int signo)
 int main(int argc, char* argv[])
 {
     struct arguments arguments;
-    char*            logfile  = "/tmp/xce_scheduler.log";
+    char*            logfile  = SCHED_DEFAULT_LOG_PATH;
     char*            loglevel = "info";
     int              logsize  = 64 * 1024 * 1024;
     int              logcount = 10;
@@ -387,6 +387,7 @@ int main(int argc, char* argv[])
         sim_args.alt_events_path = arguments.sim_alt_events;
         sim_args.output_path     = arguments.sim_output;
         sim_args.interactive     = (arguments.interactive != 0);
+        sim_args.log_path        = logfile;
 
         rc = sched_sim_driver_run(&sim, &sim_args);
         if (rc == -ENOSYS) {

src/scheduler/src/sim.c

@@ -671,6 +671,28 @@ int sched_sim_driver_start(xce_sched_sim_driver_t* sim,
         }
     }
 
+    /* scheduler-sim-decision-trace task 4.4 (Req 8.3): keep our own copy of
+     * the scheduler log path (argv memory belongs to the caller); with no
+     * --logfile the scheduler logs to SCHED_DEFAULT_LOG_PATH. */
+    sim->log_path = strdup((args->log_path != NULL) ? args->log_path
+                                                    : SCHED_DEFAULT_LOG_PATH);
+    if (sim->log_path == NULL) {
+        ERROR("%s cannot copy the scheduler log path: out of memory",
+              __func__);
+        if (sim->record_file != NULL) {
+            fclose(sim->record_file);
+            sim->record_file = NULL;
+        }
+        if (sim->alt_events_file != NULL) {
+            fclose(sim->alt_events_file);
+            sim->alt_events_file = NULL;
+        }
+        fclose(sim->replay_file);
+        sim->replay_file = NULL;
+        xce_sched_core_fini(&(sim->core));
+        return -ENOMEM;
+    }
+
     return 0;
 }
 
@@ -753,6 +775,9 @@ void sched_sim_driver_fini(xce_sched_sim_driver_t* sim)
         sim->replay_file = NULL;
     }
 
+    free(sim->log_path);
+    sim->log_path = NULL;
+
     sim_take_alloc_wrappers_(sim, wrappers);
     xce_sched_core_fini(&(sim->core));
     sim_free_alloc_wrappers_(wrappers);

src/scheduler/testsuite/test_sim_startup.c

@@ -588,6 +588,77 @@ static void test_null_arguments_return_einval(void)
     printf("test_null_arguments_return_einval: PASS\n");
 }
 
+/* ---------------------------------------------------------------------- */
+/* Test 6 (scheduler-sim-decision-trace task 4.4, Req 8.3): the driver     */
+/* holds the scheduler log path it was started with -- its own copy, not   */
+/* the caller's buffer -- or SCHED_DEFAULT_LOG_PATH (the same default      */
+/* main.c logs to without --logfile) when none is given. The trace-file    */
+/* checks compare a trace file against this path.                          */
+/* ---------------------------------------------------------------------- */
+
+static void test_driver_holds_configured_log_path(void)
+{
+    char                   path[PATH_MAX];
+    char                   log_path[PATH_MAX + 16];
+    uint64_t               snapshot_ts = 0;
+    sched_sim_args_t       args;
+    xce_sched_sim_driver_t sim;
+    int                    rc;
+
+    write_valid_fixture(path, sizeof(path), &snapshot_ts, "_logpath");
+    snprintf(log_path, sizeof(log_path), "%s.sched.log", path);
+
+    memset(&args, 0, sizeof(args));
+    args.replay_path  = path;
+    args.sim_start_ts = SCHED_SIM_START_TS_LATEST;
+    args.log_path     = log_path;
+
+    rc = sched_sim_driver_start(&sim, &args);
+    TEST_ASSERT_EQUAL_INT(0, rc);
+
+    TEST_ASSERT_NOT_NULL(sim.log_path);
+    TEST_ASSERT_EQUAL_STRING(log_path, sim.log_path);
+    TEST_ASSERT_TRUE(sim.log_path != log_path); /* owned copy */
+
+    /* The caller's buffer going away must not change the driver's path. */
+    memset(log_path, 'x', sizeof(log_path) - 1);
+    TEST_ASSERT_EQUAL_STRING_LEN(path, sim.log_path, strlen(path));
+
+    xce_core_set_active_for_logging(NULL);
+    sched_sim_driver_fini(&sim);
+    TEST_ASSERT_NULL(sim.log_path);
+
+    printf("test_driver_holds_configured_log_path: PASS\n");
+}
+
+static void test_driver_holds_default_log_path_when_none_given(void)
+{
+    char                   path[PATH_MAX];
+    uint64_t               snapshot_ts = 0;
+    sched_sim_args_t       args;
+    xce_sched_sim_driver_t sim;
+    int                    rc;
+
+    write_valid_fixture(path, sizeof(path), &snapshot_ts, "_logdefault");
+
+    memset(&args, 0, sizeof(args));
+    args.replay_path  = path;
+    args.sim_start_ts = SCHED_SIM_START_TS_LATEST;
+
+    rc = sched_sim_driver_start(&sim, &args);
+    TEST_ASSERT_EQUAL_INT(0, rc);
+
+    TEST_ASSERT_NOT_NULL(sim.log_path);
+    TEST_ASSERT_EQUAL_STRING(SCHED_DEFAULT_LOG_PATH, sim.log_path);
+    TEST_ASSERT_EQUAL_STRING("/tmp/xce_scheduler.log", sim.log_path);
+
+    xce_core_set_active_for_logging(NULL);
+    sched_sim_driver_fini(&sim);
+    TEST_ASSERT_NULL(sim.log_path);
+
+    printf("test_driver_holds_default_log_path_when_none_given: PASS\n");
+}
+
 /* Test 6 (sched_sim_driver_run() -- design.md's literal entry point --
  * calling start() then failing loudly with -ENOSYS pending the event loop)
  * was removed here: the event loop now exists (scheduler-core spec, task
@@ -607,6 +678,8 @@ int main(void)
     RUN_TEST(test_first_message_not_replayheader_fails_cleanly);
     RUN_TEST(test_missing_replay_file_fails_cleanly);
     RUN_TEST(test_null_arguments_return_einval);
+    RUN_TEST(test_driver_holds_configured_log_path);
+    RUN_TEST(test_driver_holds_default_log_path_when_none_given);
 
     return UNITY_END();
 }