fixed GH #990: Potential race condition in on Windows

Foundation/include/Poco/Exception.h

@@ -248,6 +248,7 @@ POCO_DECLARE_EXCEPTION(Foundation_API, CreateFileException, FileException)
 POCO_DECLARE_EXCEPTION(Foundation_API, OpenFileException, FileException)
 POCO_DECLARE_EXCEPTION(Foundation_API, WriteFileException, FileException)
 POCO_DECLARE_EXCEPTION(Foundation_API, ReadFileException, FileException)
+POCO_DECLARE_EXCEPTION(Foundation_API, DirectoryNotEmptyException, FileException)
 POCO_DECLARE_EXCEPTION(Foundation_API, UnknownURISchemeException, RuntimeException)
 POCO_DECLARE_EXCEPTION(Foundation_API, TooManyURIRedirectsException, RuntimeException)
 POCO_DECLARE_EXCEPTION(Foundation_API, URISyntaxException, SyntaxException)

Foundation/src/Exception.cpp

@@ -171,6 +171,7 @@ POCO_IMPLEMENT_EXCEPTION(CreateFileException, FileException, "Cannot create file
 POCO_IMPLEMENT_EXCEPTION(OpenFileException, FileException, "Cannot open file")
 POCO_IMPLEMENT_EXCEPTION(WriteFileException, FileException, "Cannot write file")
 POCO_IMPLEMENT_EXCEPTION(ReadFileException, FileException, "Cannot read file")
+POCO_IMPLEMENT_EXCEPTION(DirectoryNotEmptyException, FileException, "Directory not empty")
 POCO_IMPLEMENT_EXCEPTION(UnknownURISchemeException, RuntimeException, "Unknown URI scheme")
 POCO_IMPLEMENT_EXCEPTION(TooManyURIRedirectsException, RuntimeException, "Too many URI redirects")
 POCO_IMPLEMENT_EXCEPTION(URISyntaxException, SyntaxException, "Bad URI syntax")

Foundation/src/File.cpp

@@ -34,6 +34,7 @@
 #else
 #include "File_VMS.cpp"
 #endif
+#include "Poco/Thread.h"
 
 
 namespace Poco {
@@ -269,8 +270,37 @@ void File::remove(bool recursive)
 		{
 			it->remove(true);
 		}
+
+		// Note: On Windows, removing a directory may not succeed at first 
+		// try because deleting files is not a synchronous operation. Files
+		// are merely marked as deleted, and actually removed at a later time.
+		//
+		// An alternate strategy would be moving files to a different directory
+		// first (on the same drive, but outside the deleted tree), and marking
+		// them as hidden, before deleting them, but this could lead to other issues.
+		// So we simply retry after some time until we succeed, or give up.
+
+		int retry = 8;
+		long sleep = 10;
+		while (retry > 0)
+		{ 
+			try
+			{
+				removeImpl();
+				retry = 0;
+			}
+			catch (DirectoryNotEmptyException&)
+			{
+				if (--retry == 0) throw;
+				Poco::Thread::sleep(sleep);
+				sleep *= 2;
+			}
+		}
+	}
+	else
+	{
+		removeImpl();
 	}
-	removeImpl();
 }
 
 

Foundation/src/File_UNIX.cpp

@@ -434,7 +434,7 @@ void FileImpl::handleLastErrorImpl(const std::string& path)
 		throw FileException("disk quota exceeded", path, errno);
 #if !defined(_AIX)
 	case ENOTEMPTY:
-		throw FileException("directory not empty", path, errno);
+		throw DirectoryNotEmptyException(path, errno);
 #endif
 	case ENAMETOOLONG:
 		throw PathSyntaxException(path, errno);

Foundation/src/File_VMS.cpp

@@ -375,7 +375,7 @@ void FileImpl::handleLastErrorImpl(const std::string& path)
 	case EDQUOT:
 		throw FileException("disk quota exceeded", path);
 	case ENOTEMPTY:
-		throw FileException("directory not empty", path);
+		throw DirectoryNotEmptyException(path, err);
 	case ENAMETOOLONG:
 		throw PathSyntaxException(path);
 	default:

Foundation/src/File_VX.cpp

@@ -353,7 +353,7 @@ void FileImpl::handleLastErrorImpl(const std::string& path)
 	case ENOSPC:
 		throw FileException("no space left on device", path);
 	case ENOTEMPTY:
-		throw FileException("directory not empty", path);
+		throw DirectoryNotEmptyException(path);
 	case ENAMETOOLONG:
 		throw PathSyntaxException(path);
 	case ENFILE:

Foundation/src/File_WIN32.cpp

@@ -376,7 +376,7 @@ void FileImpl::handleLastErrorImpl(const std::string& path)
 	case ERROR_CANNOT_MAKE:
 		throw CreateFileException(path, err);
 	case ERROR_DIR_NOT_EMPTY:
-		throw FileException("directory not empty", path, err);
+		throw DirectoryNotEmptyException(path, err);
 	case ERROR_WRITE_FAULT:
 		throw WriteFileException(path, err);
 	case ERROR_READ_FAULT:

Foundation/src/File_WIN32U.cpp

@@ -384,7 +384,7 @@ void FileImpl::handleLastErrorImpl(const std::string& path)
 	case ERROR_CANNOT_MAKE:
 		throw CreateFileException(path, err);
 	case ERROR_DIR_NOT_EMPTY:
-		throw FileException("directory not empty", path, err);
+		throw DirectoryNotEmptyException(path, err);
 	case ERROR_WRITE_FAULT:
 		throw WriteFileException(path, err);
 	case ERROR_READ_FAULT:

Foundation/src/File_WINCE.cpp

@@ -374,7 +374,7 @@ void FileImpl::handleLastErrorImpl(const std::string& path)
 	case ERROR_CANNOT_MAKE:
 		throw CreateFileException(path);
 	case ERROR_DIR_NOT_EMPTY:
-		throw FileException("directory not empty", path);
+		throw DirectoryNotEmptyException(path);
 	case ERROR_WRITE_FAULT:
 		throw WriteFileException(path);
 	case ERROR_READ_FAULT: