[libc] fix build errors (llvm#95613)

Author: SchrodingerZhu

libc/src/__support/threads/linux/rwlock.h

@@ -63,7 +63,7 @@ class WaitingQueue final : private RawMutex {
     WaitingQueue &queue;
     bool is_pshared;
 
-    LIBC_INLINE constexpr Guard(WaitingQueue &queue, bool is_pshared)
+    LIBC_INLINE Guard(WaitingQueue &queue, bool is_pshared)
         : queue(queue), is_pshared(is_pshared) {
       queue.lock(cpp::nullopt, is_pshared);
     }
@@ -189,6 +189,7 @@ class RwState {
       case Role::Writer:
         return !has_active_writer() && !has_pending_writer();
       }
+      __builtin_unreachable();
     } else
       return !has_acitve_owner();
   }

libc/src/pthread/pthread_rwlock_timedrdlock.cpp

@@ -42,8 +42,8 @@ LLVM_LIBC_FUNCTION(int, pthread_rwlock_timedrdlock,
     return EINVAL;
   case internal::AbsTimeout::Error::BeforeEpoch:
     return ETIMEDOUT;
-    // default: unreachable, all two cases are covered.
   }
+  __builtin_unreachable();
 }
 
 } // namespace LIBC_NAMESPACE

libc/src/pthread/pthread_rwlock_timedwrlock.cpp

@@ -36,8 +36,8 @@ LLVM_LIBC_FUNCTION(int, pthread_rwlock_timedwrlock,
     return EINVAL;
   case internal::AbsTimeout::Error::BeforeEpoch:
     return ETIMEDOUT;
-    // default: unreachable, all two cases are covered.
   }
+  __builtin_unreachable();
 }
 
 } // namespace LIBC_NAMESPACE

libc/test/integration/src/pthread/CMakeLists.txt

@@ -53,6 +53,7 @@ add_integration_test(
     libc.src.sys.wait.waitpid
     libc.src.stdlib.exit
     libc.src.__support.CPP.atomic
+    libc.src.__support.CPP.new
     libc.src.__support.threads.sleep
 )
 

libc/test/integration/src/pthread/pthread_rwlock_test.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/__support/CPP/atomic.h"
+#include "src/__support/CPP/new.h"
 #include "src/__support/OSUtil/syscall.h"
 #include "src/__support/threads/linux/raw_mutex.h"
 #include "src/__support/threads/linux/rwlock.h"