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      1 //===-- Support/MutexGuard.h - Acquire/Release Mutex In Scope ---*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file defines a guard for a block of code that ensures a Mutex is locked
     11 // upon construction and released upon destruction.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #ifndef LLVM_SUPPORT_MUTEXGUARD_H
     16 #define LLVM_SUPPORT_MUTEXGUARD_H
     17 
     18 #include "llvm/Support/Mutex.h"
     19 
     20 namespace llvm {
     21   /// Instances of this class acquire a given Mutex Lock when constructed and
     22   /// hold that lock until destruction. The intention is to instantiate one of
     23   /// these on the stack at the top of some scope to be assured that C++
     24   /// destruction of the object will always release the Mutex and thus avoid
     25   /// a host of nasty multi-threading problems in the face of exceptions, etc.
     26   /// @brief Guard a section of code with a Mutex.
     27   class MutexGuard {
     28     sys::Mutex &M;
     29     MutexGuard(const MutexGuard &) LLVM_DELETED_FUNCTION;
     30     void operator=(const MutexGuard &) LLVM_DELETED_FUNCTION;
     31   public:
     32     MutexGuard(sys::Mutex &m) : M(m) { M.acquire(); }
     33     ~MutexGuard() { M.release(); }
     34     /// holds - Returns true if this locker instance holds the specified lock.
     35     /// This is mostly used in assertions to validate that the correct mutex
     36     /// is held.
     37     bool holds(const sys::Mutex& lock) const { return &M == &lock; }
     38   };
     39 }
     40 
     41 #endif // LLVM_SUPPORT_MUTEXGUARD_H
     42