mruby-task: switch mrb_task_run to mrb_protect_error

mruby/throw.h is documented as a core-internal header that should not
be included from mrbgems or user code, and under MRB_USE_CXX_EXCEPTION
or MRB_USE_CXX_ABI the MRB_TRY/MRB_CATCH macros expand to C++
exception syntax that does not compile in a C source file. The
wrapping added in #6866 (commit ee82a7fcc6) accidentally tripped that
constraint.

Drop the throw.h include and use mrb_protect_error() from
mruby/error.h instead. The helper takes a body function plus
userdata, runs it under its own jmpbuf, and reports whether an
exception was caught. We re-raise via mrb_exc_raise so the visible
behavior matches the previous code: loop_running is cleared on both
success and exception, and an exception propagates back out.

Refs #6866.

Co-authored-by: Claude <noreply@anthropic.com>

mrbgems/mruby-task/src/task.c

@@ -14,7 +14,6 @@
 #include <mruby/internal.h>
 #include <mruby/proc.h>
 #include <mruby/string.h>
-#include <mruby/throw.h>
 #include <mruby/variable.h>
 #include <string.h>
 #include <stdint.h>
@@ -440,67 +439,69 @@ mrb_tick(mrb_state *mrb)
   }
 }
 
+/* Body of the main scheduler loop. Wrapped by mrb_task_run() under
+   mrb_protect_error so an exception raised from a task body unwinds
+   cleanly without leaving `loop_running` set. */
+static mrb_value
+task_run_body(mrb_state *mrb, void *ud)
+{
+  mrb_task *t;
+  (void)ud;
+
+  while (1) {
+    t = q_ready_;
+
+    /* No task ready - check if all tasks are done */
+    if (!t) {
+      mrb_task_disable_irq();
+      mrb_bool exiting = !q_ready_ && !q_waiting_ && !q_suspended_;
+      mrb_task_enable_irq();
+      if (exiting) {
+        /* All tasks are dormant - scheduler done */
+        break;
+      }
+      /* If there are tasks waiting or suspended, idle */
+      mrb_hal_task_idle_cpu(mrb);
+      continue;
+    }
+
+    /* Safety check - don't execute terminated tasks */
+    if (task_cleanup_if_stopped(mrb, t)) {
+      continue;
+    }
+
+    /* Execute task using core logic */
+    execute_task(mrb, t);
+
+    /* Move to end of ready queue if still running (round-robin) */
+    if (t->status == MRB_TASK_STATUS_READY) {
+      task_change_state(mrb, t, MRB_TASK_STATUS_READY);
+    }
+
+    /* Run incremental GC if active */
+    if (mrb->gc.state != MRB_GC_STATE_ROOT) {
+      mrb_incremental_gc(mrb);
+    }
+  }
+  return mrb_nil_value();
+}
+
 /* Main scheduler loop */
 MRB_API mrb_value
 mrb_task_run(mrb_state *mrb)
 {
-  struct mrb_jmpbuf *prev_jmp;
-  struct mrb_jmpbuf c_jmp;
-  mrb_task *t;
-
   if (mrb->task.loop_running) {
     return mrb_nil_value();
   }
   mrb->task.loop_running = TRUE;
 
-  prev_jmp = mrb->jmp;
+  mrb_bool error = FALSE;
-  MRB_TRY(&c_jmp) {
+  mrb_value result = mrb_protect_error(mrb, task_run_body, NULL, &error);
-    mrb->jmp = &c_jmp;
-
-    while (1) {
-      t = q_ready_;
-
-      /* No task ready - check if all tasks are done */
-      if (!t) {
-        mrb_task_disable_irq();
-        mrb_bool exiting = !q_ready_ && !q_waiting_ && !q_suspended_;
-        mrb_task_enable_irq();
-        if (exiting) {
-          /* All tasks are dormant - scheduler done */
-          break;
-        }
-        /* If there are tasks waiting or suspended, idle */
-        mrb_hal_task_idle_cpu(mrb);
-        continue;
-      }
-
-      /* Safety check - don't execute terminated tasks */
-      if (task_cleanup_if_stopped(mrb, t)) {
-        continue;
-      }
-
-      /* Execute task using core logic */
-      execute_task(mrb, t);
-
-      /* Move to end of ready queue if still running (round-robin) */
-      if (t->status == MRB_TASK_STATUS_READY) {
-        task_change_state(mrb, t, MRB_TASK_STATUS_READY);
-      }
-
-      /* Run incremental GC if active */
-      if (mrb->gc.state != MRB_GC_STATE_ROOT) {
-        mrb_incremental_gc(mrb);
-      }
-    }
-    mrb->jmp = prev_jmp;
-  } MRB_CATCH(&c_jmp) {
-    mrb->task.loop_running = FALSE;
-    mrb->jmp = prev_jmp;
-    MRB_THROW(prev_jmp);
-  } MRB_END_EXC(&c_jmp);
-
   mrb->task.loop_running = FALSE;
-  return mrb_nil_value();
+  if (error) {
+    mrb_exc_raise(mrb, result);
+  }
+  return result;
 }
 
 /* Single-step task execution for WASM event loop integration */