absl: remove special handling of Condition::kTrue

Condition::kTrue is used very rarely (frequently its uses even indicate
confusion and bugs). But we pay few additional branches for kTrue
on all Condition operations.
Remove that special handling and simplify logic.
PiperOrigin-RevId: 563691160
Change-Id: I76125adde4872489da069dd9c894ed73a65d1d83

1 files changed, 5 insertions, 3 deletions

diff --git a/absl/synchronization/mutex.h b/absl/synchronization/mutex.h
index 645c26d9..f2bafa97 100644
--- a/absl/synchronization/mutex.h
+++ b/absl/synchronization/mutex.h
@@ -807,10 +807,10 @@ class Condition {
 #endif
 
   // Function with which to evaluate callbacks and/or arguments.
-  bool (*eval_)(const Condition*) = nullptr;
+  bool (*const eval_)(const Condition*);
 
   // Either an argument for a function call or an object for a method call.
-  void* arg_ = nullptr;
+  void* const arg_;
 
   // Various functions eval_ can point to:
   static bool CallVoidPtrFunction(const Condition*);
@@ -833,8 +833,10 @@ class Condition {
     std::memcpy(callback, callback_, sizeof(*callback));
   }
 
+  static bool AlwaysTrue(const Condition*) { return true; }
+
   // Used only to create kTrue.
-  constexpr Condition() = default;
+  constexpr Condition() : eval_(AlwaysTrue), arg_(nullptr) {}
 };
 
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