yiguolei commented on code in PR #39470:
URL: https://github.com/apache/doris/pull/39470#discussion_r1720872532
##########
be/src/util/once.h:
##########
@@ -42,95 +48,67 @@ namespace doris {
// }
//
// bool is_inited() const {
-// return _init_once.has_called() && _init_once.stored_result().ok();
+// return _init_once.is_called() && _init_once.stored_result().ok();
// }
// private:
// Status _do_init() { /* init logic here */ }
// DorisCallOnce<Status> _init_once;
// };
-template <typename ReturnType>
+
+template <typename R>
class DorisCallOnce {
public:
- DorisCallOnce() : _has_called(false) {}
-
- // this method is not exception safe, it will core when exception occurs in
- // callback method. I have tested the code
https://en.cppreference.com/w/cpp/thread/call_once.
- // If the underlying `once_flag` has yet to be invoked, invokes the
provided
- // lambda and stores its return value. Otherwise, returns the stored
Status.
- // template <typename Fn>
- // ReturnType call(Fn fn) {
- // std::call_once(_once_flag, [this, fn] {
- // _status = fn();
- // _has_called.store(true, std::memory_order_release);
- // });
- // return _status;
- // }
+ DorisCallOnce() : _eptr(nullptr), _is_exception_thrown(false),
_ret_val(std::nullopt) {}
- // If exception occurs in the function, the call flag is set, if user call
- // it again, the same exception will be thrown.
- // It is different from std::call_once. This is because if a method is
called once
- // some internal state is changed, it maybe not called again although
exception
- // occurred.
template <typename Fn>
- ReturnType call(Fn fn) {
- // Avoid lock to improve performance
- if (has_called()) {
- if (_eptr) {
- std::rethrow_exception(_eptr);
+ requires std::is_invocable_r_v<R, Fn>
+ R call(Fn fn) {
+ std::call_once(_once_flag, [&] {
Review Comment:
In the past, we use std call once, but there are 2 main reasons that we
implement our own call once:
1. std call once could not deal with exception logic correctly.
2. when it is core during std call once, it's callstack will include another
thread, it is not very clear.
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