Apply ABSL_MUST_USE_RESULT to try lock functions.

PiperOrigin-RevId: 628091370
Change-Id: I2dd20b7f33ab99e78d63688832ab475a513aa3fd

absl/base/internal/spinlock.h

@@ -89,7 +89,8 @@ class ABSL_LOCKABLE ABSL_ATTRIBUTE_WARN_UNUSED SpinLock {
   // acquisition was successful.  If the lock was not acquired, false is
   // returned.  If this SpinLock is free at the time of the call, TryLock
   // will return true with high probability.
-  inline bool TryLock() ABSL_EXCLUSIVE_TRYLOCK_FUNCTION(true) {
+  ABSL_MUST_USE_RESULT inline bool TryLock()
+      ABSL_EXCLUSIVE_TRYLOCK_FUNCTION(true) {
     ABSL_TSAN_MUTEX_PRE_LOCK(this, __tsan_mutex_try_lock);
     bool res = TryLockImpl();
     ABSL_TSAN_MUTEX_POST_LOCK(
@@ -120,7 +121,7 @@ class ABSL_LOCKABLE ABSL_ATTRIBUTE_WARN_UNUSED SpinLock {
   // Determine if the lock is held.  When the lock is held by the invoking
   // thread, true will always be returned. Intended to be used as
   // CHECK(lock.IsHeld()).
-  inline bool IsHeld() const {
+  ABSL_MUST_USE_RESULT inline bool IsHeld() const {
     return (lockword_.load(std::memory_order_relaxed) & kSpinLockHeld) != 0;
   }
 

absl/synchronization/mutex.h

@@ -190,7 +190,7 @@ class ABSL_LOCKABLE ABSL_ATTRIBUTE_WARN_UNUSED Mutex {
   // If the mutex can be acquired without blocking, does so exclusively and
   // returns `true`. Otherwise, returns `false`. Returns `true` with high
   // probability if the `Mutex` was free.
-  bool TryLock() ABSL_EXCLUSIVE_TRYLOCK_FUNCTION(true);
+  ABSL_MUST_USE_RESULT bool TryLock() ABSL_EXCLUSIVE_TRYLOCK_FUNCTION(true);
 
   // Mutex::AssertHeld()
   //
@@ -255,7 +255,7 @@ class ABSL_LOCKABLE ABSL_ATTRIBUTE_WARN_UNUSED Mutex {
   // If the mutex can be acquired without blocking, acquires this mutex for
   // shared access and returns `true`. Otherwise, returns `false`. Returns
   // `true` with high probability if the `Mutex` was free or shared.
-  bool ReaderTryLock() ABSL_SHARED_TRYLOCK_FUNCTION(true);
+  ABSL_MUST_USE_RESULT bool ReaderTryLock() ABSL_SHARED_TRYLOCK_FUNCTION(true);
 
   // Mutex::AssertReaderHeld()
   //
@@ -281,7 +281,8 @@ class ABSL_LOCKABLE ABSL_ATTRIBUTE_WARN_UNUSED Mutex {
 
   void WriterUnlock() ABSL_UNLOCK_FUNCTION() { this->Unlock(); }
 
-  bool WriterTryLock() ABSL_EXCLUSIVE_TRYLOCK_FUNCTION(true) {
+  ABSL_MUST_USE_RESULT bool WriterTryLock()
+      ABSL_EXCLUSIVE_TRYLOCK_FUNCTION(true) {
     return this->TryLock();
   }