A LPWSTR problem, help please!!!

Hi guys,

I'm writing a speech recognition application using Microsoft SAPI. SAPI provides a function called LoadCmdFromFile() to load a grammar file for the speech recognition engine to use. It is defined like this:

Code:

HRESULT LoadCmdFromFile(
    LPCWSTR        *pszFileName,
      
    SPLOADOPTIONS   Options
);

Now I have a global variable LPCWSTR gramFile. and have the following functions to help me to determine the value of gramFile:

Code:

std::wstring GVC::s2ws(const std::string& s)
{
	int len;
	int slength = (int)s.length() + 1;
	len = MultiByteToWideChar(CP_ACP, 0, s.c_str(), slength, 0, 0); 
	 wchar_t* buf = new wchar_t[len];
	MultiByteToWideChar(CP_ACP, 0, s.c_str(), slength, buf, len);
	std::wstring r(buf);
	delete[] buf;
	return r;
}

void GVC::open()
{
	QString fileName = QFileDialog::getOpenFileName(this);
	if(!fileName.isEmpty())
	{
		QFile file(fileName);
		if(!file.open(QFile::ReadOnly))
		{
			QString msg = tr("Failed to open %1\n%2").arg(fileName).arg(file.errorString());
			QMessageBox::warning(this, tr("Error"), msg);
			return;
		}
		QDomDocument doc("grammar");
		if(!doc.setContent(&file))
		{
			file.close();
			return;
		}
		file.close();
		std::string s = fileName.toStdString();
		std::wstring ws = s2ws(s);
		gramFile = ws.c_str();
}

Now the start() function will then use the file name contained in gramFile in order to start the engine.

Code:

void GVC::start()
{
	if(!srh->isRecognizing)
	{
                //if I set its value manually the file will be loaded and everything works fine.
                //gramFile = L"Test.xml";


		srh->initEngine(gramFile); // initialize the attributes of the engine, grammFile is directly passed to LoadCmdFromFile();
		timer->start(12);
		ui.statusLabel->setText("Game voice control has started.");
	}
}

If I set the value of gramFile manually then it will be loaded and everything will work. But when I use the functions that I showed above, it wont.

I tried to debug it and noticed that the value of gramFile at the end of the open() function is a correct path like:"D:/Test.xml". However when I press a button that calls the start() function, the value of gramFile changed to:"ﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮ ﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮﻮJŢިĘ﷈Ͼ龘ϷာƲ". Which obviously doesn't mean anything. I think this is the source that causes the problem but I don't know what went wrong and how to fix it.

Would any of you help out on this one?

Many thanks!

The memory returned by "ws.c_str()" is no longer valid when "ws" is no longer value. They have the same "lifetime".

gg

Thank you Codeplug! I've fixed it now.

Ha! When I started reading this thread, I thought, "Hmm, looks like a question for Codeplug" (ie: "master of the code-page"). How ironic.