Merge pull request #5415 from dearblue/unwind-mrb_protect

Introducing the `mrb_protect_raw()` API function

src/vm.c

@@ -306,6 +306,49 @@ cipop(mrb_state *mrb)
   return c->ci;
 }
 
+MRB_API mrb_value
+mrb_protect_raw(mrb_state *mrb, mrb_protect_raw_func *body, void *userdata, mrb_bool *error)
+{
+  struct mrb_jmpbuf *prev_jmp = mrb->jmp;
+  struct mrb_jmpbuf c_jmp;
+  mrb_value result = mrb_nil_value();
+  int ai = mrb_gc_arena_save(mrb);
+  const struct mrb_context *c = mrb->c;
+  int ci_index = c->ci - c->cibase;
+
+  if (error) { *error = FALSE; }
+
+  MRB_TRY(&c_jmp) {
+    mrb->jmp = &c_jmp;
+    result = body(mrb, userdata);
+    mrb->jmp = prev_jmp;
+  }
+  MRB_CATCH(&c_jmp) {
+    mrb->jmp = prev_jmp;
+    result = mrb_obj_value(mrb->exc);
+    mrb->exc = NULL;
+    if (error) { *error = TRUE; }
+    if (mrb->c == c) {
+      while (c->ci - c->cibase > ci_index) {
+        cipop(mrb);
+      }
+    }
+    else {
+      // It was probably switched by mrb_fiber_resume().
+      // Simply destroy all successive CI_ACC_DIRECTs once the fiber has been switched.
+      c = mrb->c;
+      while (c->ci > c->cibase && c->ci->acc == CI_ACC_DIRECT) {
+        cipop(mrb);
+      }
+    }
+  }
+  MRB_END_EXC(&c_jmp);
+
+  mrb_gc_arena_restore(mrb, ai);
+  mrb_gc_protect(mrb, result);
+  return result;
+}
+
 void mrb_exc_set(mrb_state *mrb, mrb_value exc);
 static mrb_value mrb_run(mrb_state *mrb, const struct RProc* proc, mrb_value self);