Begin sketching out the process interface.

The coding style used here is not LLVM's style because this is modeled
after a Boost interface and thus done in the style of a candidate C++
standard library interface. I'll probably end up proposing it as
a standard C++ library if it proves to be reasonably portable and
useful.

This is just the most basic parts of the interface -- getting the
process ID out of it. However, it helps sketch out some of the boiler
plate such as the base class, derived class, shared code, and static
factory function. It also introduces a unittest so that I can
incrementally ensure this stuff works.

However, I've not even compiled this code for Windows yet. I'll try to
fix any Windows fallout from the bots, and if I can't fix it I'll revert
and get someone on Windows to help out. There isn't a lot more that is
mandatory, so soon I'll switch to just stubbing out the Windows side and
get Michael Spencer to help with implementation as he can test it
directly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171289 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/Process.h

@@ -25,11 +25,74 @@
 #ifndef LLVM_SYSTEM_PROCESS_H
 #define LLVM_SYSTEM_PROCESS_H
 
+#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/DataTypes.h"
 #include "llvm/Support/TimeValue.h"
 
 namespace llvm {
 namespace sys {
 
+class self_process;
+
+/// \brief Generic base class which exposes information about an operating
+/// system process.
+///
+/// This base class is the core interface behind any OS process. It exposes
+/// methods to query for generic information about a particular process.
+///
+/// Subclasses implement this interface based on the mechanisms available, and
+/// can optionally expose more interfaces unique to certain process kinds.
+class process {
+protected:
+  /// \brief Only specific subclasses of process objects can be destroyed.
+  virtual ~process();
+
+public:
+  /// \brief Operating system specific type to identify a process.
+  ///
+  /// Note that the windows one is defined to 'void *' as this is the
+  /// documented type for HANDLE on windows, and we don't want to pull in the
+  /// Windows headers here.
+#if defined(LLVM_ON_UNIX)
+  typedef pid_t id_type;
+#elif defined(LLVM_ON_WIN32)
+  typedef void *id_type; // Must match the type of HANDLE.
+#else
+#error Unsupported operating system.
+#endif
+
+  /// \brief Get the operating system specific identifier for this process.
+  virtual id_type get_id() = 0;
+
+
+  /// \name Static factory routines for processes.
+  /// @{
+
+  /// \brief Get the process object for the current process.
+  static self_process *get_self();
+
+  /// @}
+
+};
+
+/// \brief The specific class representing the current process.
+///
+/// The current process can both specialize the implementation of the routines
+/// and can expose certain information not available for other OS processes.
+class self_process : public process {
+  friend class process;
+
+  /// \brief Private destructor, as users shouldn't create objects of this
+  /// type.
+  virtual ~self_process();
+
+public:
+  virtual id_type get_id();
+
+private:
+};
+
+
 /// \brief A collection of legacy interfaces for querying information about the
 /// current executing process.
 class Process {

lib/Support/Process.cpp

@@ -11,8 +11,9 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/Support/Process.h"
 #include "llvm/Config/config.h"
+#include "llvm/Support/Process.h"
+#include "llvm/Support/ErrorHandling.h"
 
 namespace llvm {
 using namespace sys;
@@ -22,6 +23,25 @@ using namespace sys;
 //===          independent code.
 //===----------------------------------------------------------------------===//
 
+// Empty virtual destructor to anchor the vtable for the process class.
+process::~process() {}
+
+self_process *process::get_self() {
+  // Use a function local static for thread safe initialization and allocate it
+  // as a raw pointer to ensure it is never destroyed.
+  static self_process *SP = new self_process();
+
+  return SP;
+}
+
+// The destructor for the self_process subclass must never actually be
+// executed. There should be at most one instance of this class, and that
+// instance should live until the process terminates to avoid the potential for
+// racy accesses during shutdown.
+self_process::~self_process() {
+  llvm_unreachable("This destructor must never be executed!");
+}
+
 }
 
 // Include the platform-specific parts of this class.

lib/Support/Unix/Process.inc

@@ -44,6 +44,12 @@
 using namespace llvm;
 using namespace sys;
 
+
+process::id_type self_process::get_id() {
+  return getpid();
+}
+
+
 unsigned
 Process::GetPageSize()
 {

lib/Support/Windows/Process.inc

@@ -38,6 +38,12 @@
 namespace llvm {
 using namespace sys;
 
+
+process::id_type self_process::get_id() {
+  return GetCurrentProcess();
+}
+
+
 // This function retrieves the page size using GetSystemInfo and is present
 // solely so it can be called once in Process::GetPageSize to initialize the
 // static variable PageSize.

unittests/Support/CMakeLists.txt

@@ -20,6 +20,7 @@ add_llvm_unittest(SupportTests
   MemoryBufferTest.cpp
   MemoryTest.cpp
   Path.cpp
+  ProcessTest.cpp
   RegexTest.cpp
   SwapByteOrderTest.cpp
   TimeValue.cpp

unittests/Support/ProcessTest.cpp

@@ -0,0 +1,33 @@
+//===- unittest/Support/ProcessTest.cpp -----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Process.h"
+#include "gtest/gtest.h"
+
+#ifdef LLVM_ON_WIN32
+#include "windows.h"
+#endif
+
+namespace {
+
+using namespace llvm;
+using namespace sys;
+
+TEST(ProcessTest, SelfProcess) {
+  EXPECT_TRUE(process::get_self());
+  EXPECT_EQ(process::get_self(), process::get_self());
+
+#if defined(LLVM_ON_UNIX)
+  EXPECT_EQ(getpid(), process::get_self()->get_id());
+#elif defined(LLVM_ON_WIN32)
+  EXPECT_EQ(GetCurrentProcess(), process::get_self()->get_id());
+#endif
+}
+
+} // end anonymous namespace