Use TempFile in the implementation of LockFileManager.

This move some of the complexity over to the lower level TempFile.

It also makes it a bit more explicit where errors are ignored since we
now have a call to consumeError.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318550 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/LockFileManager.h

@@ -11,6 +11,7 @@
 
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/Support/FileSystem.h"
 #include <system_error>
 #include <utility> // for std::pair
 
@@ -53,7 +54,7 @@ class LockFileManager {
 private:
   SmallString<128> FileName;
   SmallString<128> LockFileName;
-  SmallString<128> UniqueLockFileName;
+  Optional<sys::fs::TempFile> UniqueLockFile;
 
   Optional<std::pair<std::string, int> > Owner;
   std::error_code ErrorCode;

lib/Support/LockFileManager.cpp

@@ -123,33 +123,21 @@ bool LockFileManager::processStillExecuting(StringRef HostID, int PID) {
 
 namespace {
 
-/// An RAII helper object ensure that the unique lock file is removed.
-///
-/// Ensures that if there is an error or a signal before we finish acquiring the
-/// lock, the unique file will be removed. And if we successfully take the lock,
-/// the signal handler is left in place so that signals while the lock is held
-/// will remove the unique lock file. The caller should ensure there is a
-/// matching call to sys::DontRemoveFileOnSignal when the lock is released.
-class RemoveUniqueLockFileOnSignal {
-  StringRef Filename;
-  bool RemoveImmediately;
+/// An RAII helper object for cleanups.
+class RAIICleanup {
+  std::function<void()> Fn;
+  bool Canceled = false;
+
 public:
-  RemoveUniqueLockFileOnSignal(StringRef Name)
-  : Filename(Name), RemoveImmediately(true) {
-    sys::RemoveFileOnSignal(Filename, nullptr);
-  }
+  RAIICleanup(std::function<void()> Fn) : Fn(Fn) {}
 
-  ~RemoveUniqueLockFileOnSignal() {
-    if (!RemoveImmediately) {
-      // Leave the signal handler enabled. It will be removed when the lock is
-      // released.
+  ~RAIICleanup() {
+    if (Canceled)
       return;
-    }
-    sys::fs::remove(Filename);
-    sys::DontRemoveFileOnSignal(Filename);
+    Fn();
   }
 
-  void lockAcquired() { RemoveImmediately = false; }
+  void cancel() { Canceled = true; }
 };
 
 } // end anonymous namespace
@@ -172,16 +160,22 @@ LockFileManager::LockFileManager(StringRef FileName)
     return;
 
   // Create a lock file that is unique to this instance.
-  UniqueLockFileName = LockFileName;
-  UniqueLockFileName += "-%%%%%%%%";
-  int UniqueLockFileID;
-  if (std::error_code EC = sys::fs::createUniqueFile(
-          UniqueLockFileName, UniqueLockFileID, UniqueLockFileName)) {
-    std::string S("failed to create unique file ");
-    S.append(UniqueLockFileName.str());
+  Expected<sys::fs::TempFile> Temp =
+      sys::fs::TempFile::create(LockFileName + "-%%%%%%%%");
+  if (!Temp) {
+    std::error_code EC = errorToErrorCode(Temp.takeError());
+    std::string S("failed to create unique file with prefix ");
+    S.append(LockFileName.str());
     setError(EC, S);
     return;
   }
+  UniqueLockFile = std::move(*Temp);
+
+  // Make sure we discard the temporary file on exit.
+  RAIICleanup RemoveTempFile([&]() {
+    if (Error E = UniqueLockFile->discard())
+      setError(errorToErrorCode(std::move(E)));
+  });
 
   // Write our process ID to our unique lock file.
   {
@@ -191,54 +185,46 @@ LockFileManager::LockFileManager(StringRef FileName)
       return;
     }
 
-    raw_fd_ostream Out(UniqueLockFileID, /*shouldClose=*/true);
+    raw_fd_ostream Out(UniqueLockFile->FD, /*shouldClose=*/false);
     Out << HostID << ' ';
 #if LLVM_ON_UNIX
     Out << getpid();
 #else
     Out << "1";
 #endif
-    Out.close();
+    Out.flush();
 
     if (Out.has_error()) {
       // We failed to write out PID, so report the error, remove the
       // unique lock file, and fail.
       std::string S("failed to write to ");
-      S.append(UniqueLockFileName.str());
+      S.append(UniqueLockFile->TmpName);
       setError(Out.error(), S);
-      sys::fs::remove(UniqueLockFileName);
       return;
     }
   }
 
-  // Clean up the unique file on signal, which also releases the lock if it is
-  // held since the .lock symlink will point to a nonexistent file.
-  RemoveUniqueLockFileOnSignal RemoveUniqueFile(UniqueLockFileName);
-
   while (true) {
     // Create a link from the lock file name. If this succeeds, we're done.
     std::error_code EC =
-        sys::fs::create_link(UniqueLockFileName, LockFileName);
+        sys::fs::create_link(UniqueLockFile->TmpName, LockFileName);
     if (!EC) {
-      RemoveUniqueFile.lockAcquired();
+      RemoveTempFile.cancel();
       return;
     }
 
     if (EC != errc::file_exists) {
       std::string S("failed to create link ");
       raw_string_ostream OSS(S);
-      OSS << LockFileName.str() << " to " << UniqueLockFileName.str();
+      OSS << LockFileName.str() << " to " << UniqueLockFile->TmpName;
       setError(EC, OSS.str());
       return;
     }
 
     // Someone else managed to create the lock file first. Read the process ID
     // from the lock file.
-    if ((Owner = readLockFile(LockFileName))) {
-      // Wipe out our unique lock file (it's useless now)
-      sys::fs::remove(UniqueLockFileName);
-      return;
-    }
+    if ((Owner = readLockFile(LockFileName)))
+      return; // RemoveTempFile will delete out our unique lock file.
 
     if (!sys::fs::exists(LockFileName)) {
       // The previous owner released the lock file before we could read it.
@@ -250,7 +236,7 @@ LockFileManager::LockFileManager(StringRef FileName)
     // ownership.
     if ((EC = sys::fs::remove(LockFileName))) {
       std::string S("failed to remove lockfile ");
-      S.append(UniqueLockFileName.str());
+      S.append(LockFileName.str());
       setError(EC, S);
       return;
     }
@@ -285,10 +271,7 @@ LockFileManager::~LockFileManager() {
 
   // Since we own the lock, remove the lock file and our own unique lock file.
   sys::fs::remove(LockFileName);
-  sys::fs::remove(UniqueLockFileName);
-  // The unique file is now gone, so remove it from the signal handler. This
-  // matches a sys::RemoveFileOnSignal() in LockFileManager().
-  sys::DontRemoveFileOnSignal(UniqueLockFileName);
+  consumeError(UniqueLockFile->discard());
 }
 
 LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() {