lldb/unittests/TestingSupport/SubsystemRAII.h

   1 //===- SubsystemRAII.h ------------------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLDB_UNITTESTS_TESTINGSUPPORT_SUBSYSTEMRAII_H
  10 #define LLDB_UNITTESTS_TESTINGSUPPORT_SUBSYSTEMRAII_H
  11
  12 #include "llvm/Support/Error.h"
  13 #include "llvm/Testing/Support/Error.h"
  14 #include "gtest/gtest.h"
  15 #include <type_traits>
  16
  17 namespace lldb_private {
  18
  19 namespace detail {
  20 /// Initializes and deinitializes a single subsystem.
  21 /// @see SubsystemRAII
  22 template <typename T> struct SubsystemRAIICase {
  23
  24   /// Calls ::Initialize if it has a void return type.
  25   template <typename U = T>
  26   typename std::enable_if<
  27       std::is_same<decltype(U::Initialize()), void>::value>::type
  28   CallInitialize() {
  29     T::Initialize();
  30   }
  31
  32   /// Calls ::Initialize if it has a llvm::Error return type and checks
  33   /// the Error instance for success.
  34   template <typename U = T>
  35   typename std::enable_if<
  36       std::is_same<decltype(U::Initialize()), llvm::Error>::value>::type
  37   CallInitialize() {
  38     ASSERT_THAT_ERROR(T::Initialize(), llvm::Succeeded());
  39   }
  40
  41   SubsystemRAIICase() { CallInitialize(); }
  42   ~SubsystemRAIICase() { T::Terminate(); }
  43 };
  44 } // namespace detail
  45
  46 template <typename... T> class SubsystemRAII {};
  47
  48 /// RAII for initializing and deinitializing LLDB subsystems.
  49 ///
  50 /// This RAII takes care of calling the Initialize and Terminate functions for
  51 /// the subsystems specified by its template arguments. The ::Initialize
  52 /// functions are called on construction for each subsystem template parameter
  53 /// in the order in which they are passed as template parameters.
  54 /// The ::Terminate functions are called in the reverse order at destruction
  55 /// time.
  56 ///
  57 /// If the ::Initialize function returns an llvm::Error this function handles
  58 /// the Error instance (by checking that there is no error).
  59 ///
  60 /// Constructing this RAII in a scope like this:
  61 ///
  62 ///   @code{.cpp}
  63 ///   {
  64 ///     SubsystemRAII<FileSystem, HostInfo, Socket> Subsystems;
  65 ///     DoingTestWork();
  66 ///   }
  67 ///   @endcode
  68 ///
  69 /// is equivalent to the following code:
  70 ///
  71 ///   @code{.cpp}
  72 ///   {
  73 ///     FileSystem::Initialize();
  74 ///     HostInfo::Initialize();
  75 ///     ASSERT_THAT_ERROR(Socket::Initialize(), llvm::Succeeded());
  76 ///
  77 ///     DoingTestWork();
  78 ///
  79 ///     Socket::Terminate();
  80 ///     FileSystem::Terminate();
  81 ///     HostInfo::Terminate();
  82 ///   }
  83 ///   @endcode
  84 template <typename T, typename... Ts> class SubsystemRAII<T, Ts...> {
  85   detail::SubsystemRAIICase<T> CurrentSubsystem;
  86   SubsystemRAII<Ts...> RemainingSubsystems;
  87 };
  88 } // namespace lldb_private
  89
  90 #endif // LLDB_UNITTESTS_TESTINGSUPPORT_SUBSYSTEMRAII_H