From 324243fa90e199012a81bf08b232a9d523ce1fbf Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris+github@qwirx.com>
Date: Mon, 13 Apr 2015 17:59:30 +0000
Subject: Fix file locking on Windows.

NamedLock simply didn't work before. This may cause test failures, but the
tests are already failing on Windows, and must be fixed.
---
 lib/common/NamedLock.cpp | 39 +++++++++++++++++++++++++++++++++++----
 lib/common/NamedLock.h   |  1 +
 2 files changed, 36 insertions(+), 4 deletions(-)

(limited to 'lib')

diff --git a/lib/common/NamedLock.cpp b/lib/common/NamedLock.cpp
index 3c2c99dd..fadf4df3 100644
--- a/lib/common/NamedLock.cpp
+++ b/lib/common/NamedLock.cpp
@@ -73,6 +73,8 @@ bool NamedLock::TryAndGetLock(const std::string& rFilename, int mode)
 		THROW_EXCEPTION(CommonException, NamedLockAlreadyLockingSomething)
 	}
 
+	mFileName = rFilename;
+
 	// See if the lock can be got
 #if HAVE_DECL_O_EXLOCK
 	int fd = ::open(rFilename.c_str(),
@@ -94,11 +96,28 @@ bool NamedLock::TryAndGetLock(const std::string& rFilename, int mode)
 
 	return false;
 #else
-	int fd = ::open(rFilename.c_str(), O_WRONLY | O_CREAT | O_TRUNC, mode);
+	int flags = O_WRONLY | O_CREAT | O_TRUNC;
+
+# if !HAVE_DECL_F_SETLK && !defined HAVE_FLOCK
+	// We have no other way to get a lock, so all we can do is fail if
+	// the file already exists, and take the risk of stale locks.
+	flags |= O_EXCL;
+# endif
+
+	int fd = ::open(rFilename.c_str(), flags, mode);
 	if(fd == -1)
 	{
-		THROW_SYS_FILE_ERROR("Failed to open lockfile", rFilename,
-			CommonException, OSFileError);
+		if(errno == EEXIST && (flags & O_EXCL))
+		{
+			// Lockfile already exists, and we tried to open it
+			// exclusively, which means we failed to lock it.
+			return false;
+		}
+		else
+		{
+			THROW_SYS_FILE_ERROR("Failed to open lockfile",
+				rFilename, CommonException, OSFileError);
+		}
 	}
 
 #ifdef HAVE_FLOCK
@@ -162,8 +181,20 @@ void NamedLock::ReleaseLock()
 	// Close the file
 	if(::close(mFileDescriptor) != 0)
 	{
-		THROW_EXCEPTION(CommonException, OSFileError)
+		THROW_EMU_ERROR(
+			BOX_FILE_MESSAGE(mFileName, "Failed to close lockfile"),
+			CommonException, OSFileError);
 	}
+
+	// Delete the file
+	if(::unlink(mFileName.c_str()) != 0)
+	{
+		THROW_EMU_ERROR(
+			BOX_FILE_MESSAGE(mFileName,
+				"Failed to delete lockfile"),
+			CommonException, OSFileError);
+	}
+
 	// Mark as unlocked
 	mFileDescriptor = -1;
 }
diff --git a/lib/common/NamedLock.h b/lib/common/NamedLock.h
index 534115db..09f5001a 100644
--- a/lib/common/NamedLock.h
+++ b/lib/common/NamedLock.h
@@ -35,6 +35,7 @@ public:
 	
 private:
 	int mFileDescriptor;
+	std::string mFileName;
 };
 
 #endif // NAMEDLOCK__H
-- 
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