Proper use of absl::Condition

[rogeeff]

I am using Abseil Synchronization primitives. I want to write a class Foo with data member int field_ protected by absl::Mutex guard_. What is the proper way to write a method of a class Foo using absl::Condition, which takes int parameter v and waits on a mutex until value of the field_ becomes equal to v?

class Foo {
public:
void WaitForValue(int v) {
absl::MutexLock lock(&guard_);

  guard_.Await(absl::Condition(
  +[](???) ABSL_EXCLUSIVE_LOCKS_REQUIRED(guard_) {
    return ???;  this->field_ == v
  },
  ???));

}
private:
absl::Mutex guard_;
int field_ ABSL_GUARDED_BY(guard_);
};

[derekmauro]

abseil-cpp/absl/synchronization/mutex.h

Lines 773 to 777 in be68967

	// auto reached = [this, current]() {
	// mu_.AssertReaderHeld(); // For annotalysis.
	// return processed_ >= current;
	// };
	// mu_.Await(Condition(&reached));

class Foo {
 public:
  void WaitForValue(int v) {
    auto reached = [this, v]() {
      return field_ == v;
    };
    absl::MutexLock lock(&guard_);
    guard_.Await(absl::Condition(&reached));
  }

 private:
  absl::Mutex guard_;
  int field_ ABSL_GUARDED_BY(guard_);
};

[rogeeff]

Thx a lot!