[Support] Prevent leaking unique lock files

[jansvoboda11]

Prior to this PR, failing to get the host ID would leave the unique lock file on the file system. This is now fixed by constructing RemoveUniqueLockFileOnSignal earlier. This PR also removes one call to sys::fs::remove() that is now redundant and another that was redundant even before this patch.

[llvmbot]

@llvm/pr-subscribers-llvm-support

Author: Jan Svoboda (jansvoboda11)

Changes

Prior to this PR, failing to get the host ID would leave the unique lock file on the file system. This is now fixed by constructing RemoveUniqueLockFileOnSignal earlier. This PR also removes one call to sys::fs::remove() that is now redundant and another that was redundant even before this patch.

---

Full diff: https://github.com/llvm/llvm-project/pull/130984.diff

1 Files Affected:

• (modified) llvm/lib/Support/LockFileManager.cpp (+5-9)

diff --git a/llvm/lib/Support/LockFileManager.cpp b/llvm/lib/Support/LockFileManager.cpp
index 7cf9db379974f..430dc1fa25fef 100644
--- a/llvm/lib/Support/LockFileManager.cpp
+++ b/llvm/lib/Support/LockFileManager.cpp
@@ -189,6 +189,10 @@ Expected<bool> LockFileManager::tryLock() {
     return createStringError(EC, "failed to create unique file " +
                                      UniqueLockFileName);
 
+  // Clean up the unique file on signal or scope exit. This also releases the
+  // lock if it's held since the .lock symlink will point to a nonexistent file.
+  RemoveUniqueLockFileOnSignal RemoveUniqueFile(UniqueLockFileName);
+
   // Write our process ID to our unique lock file.
   {
     SmallString<256> HostID;
@@ -200,21 +204,15 @@ Expected<bool> LockFileManager::tryLock() {
     Out.close();
 
     if (Out.has_error()) {
-      // We failed to write out PID, so report the error, remove the
-      // unique lock file, and fail.
+      // We failed to write out PID, so report the error and fail.
       Error Err = createStringError(Out.error(),
                                     "failed to write to " + UniqueLockFileName);
-      sys::fs::remove(UniqueLockFileName);
       // Don't call report_fatal_error.
       Out.clear_error();
       return std::move(Err);
     }
   }
 
-  // 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 =
@@ -232,8 +230,6 @@ Expected<bool> LockFileManager::tryLock() {
     // Someone else managed to create the lock file first. Read the process ID
     // from the lock file.
     if (auto LockFileOwner = readLockFile(LockFileName)) {
-      // Wipe out our unique lock file (it's useless now)
-      sys::fs::remove(UniqueLockFileName);
       Owner = std::move(*LockFileOwner);
       return false;
     }

[Bigcheese]

lgtm, but a note on one of the comments.