poco/Foundation/include/Poco/StreamUtil.h

//
// StreamUtil.h
//
// Library: Foundation
// Package: Streams
// Module:  StreamUtil
//
// Stream implementation support.
//
// Copyright (c) 2005-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_StreamUtil_INCLUDED
#define Foundation_StreamUtil_INCLUDED


#include "Poco/Foundation.h"


// poco_ios_init
//
// This is a workaround for a bug in the Dinkumware
// implementation of iostreams.
//
// Calling basic_ios::init() multiple times for the
// same basic_ios instance results in a memory leak
// caused by the ios' locale being allocated more than
// once, each time overwriting the old pointer.
// This usually occurs in the following scenario:
//
// class MyStreamBuf: public std::streambuf
// {
//     ...
// };
//
// class MyIOS: public virtual std::ios
// {
// public:
//     MyIOS()
//     {
//         init(&_buf);
//     }
// protected:
//     MyStreamBuf _buf;
// };
//
// class MyIStream: public MyIOS, public std::istream
// {
//     ...
// };
//
// In this scenario, std::ios::init() is called twice
// (the first time by the MyIOS constructor, the second
// time by the std::istream constructor), resulting in
// two locale objects being allocated, the pointer second
// one overwriting the pointer to the first one and thus
// causing a memory leak.
//
// The workaround is to call init() only once for each
// stream object - by the istream, ostream or iostream
// constructor, and not calling init() in ios-derived
// base classes.
//
// Some stream implementations, however, require that
// init() is called in the MyIOS constructor.
// Therefore we replace each call to init() with
// the poco_ios_init macro defined below.


#if !defined(POCO_IOS_INIT_HACK)
	// Microsoft Visual Studio with Dinkumware STL (but not STLport)
#	if defined(_MSC_VER) && (!defined(_STLP_MSVC) || defined(_STLP_NO_OWN_IOSTREAMS))
#		define POCO_IOS_INIT_HACK 1
    // QNX with Dinkumware but not GNU C++ Library
#	elif defined(__QNX__) && !defined(__GLIBCPP__)
#		define POCO_IOS_INIT_HACK 1
	// Linux with Clang libc++
#   elif defined(__linux) && defined(_LIBCPP_VERSION)
#		define POCO_IOS_INIT_HACK 1
#	endif
#endif


#if defined(POCO_IOS_INIT_HACK)
#	define poco_ios_init(buf)
#else
#	define poco_ios_init(buf) init(buf)
#endif


#endif // Foundation_StreamUtil_INCLUDED