Creating a timestamp with Visual c++

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I am trying to create a time stamp at the beginning of text before it is sent to a RichTextBox control. When i do this any strings over two characters get messy and garbled(see below).

C++

char* Form1::get_date(void)
{
	time_t now = time(NULL);
	tm * ptm = localtime(&now);
	char buffer[32];
	// Format: Mo, 15.06.2009 20:20:00
	strftime(buffer, 32, "%a, %d.%m.%Y %H:%M:%S", ptm);
	
	return buffer;
}
Output:
žo 02.09.2013 10:14é€ Error

char* Form1::get_date(void)
{
		
	char date[80];
	time_t t = time(0);
	struct tm *tm;
	tm = gmtime(&t);
        // Format: 20:00
	strftime(date, sizeof(date), "%M:%S", tm);

	return date;
}
Output:
17:0Àî" Error

So as you can see the string is getting changed, by changing return date; to return "12:13"; i can see that the string is being changed before it ever leaves the function above to be sent to the RTB below.

C++

void Form1::updateConsole(System::String^ text)
	{
		System::String^ consoleOutput;
		consoleOutput = gcnew String(get_date());
		rtbConsole->Text += consoleOutput;
		rtbConsole->Text += " " + text;
		rtbConsole->Text += Environment::NewLine;

	}

Any ideas of how to resolve this?

Posted 2-Sep-13 5:27am

Member 7909935

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2 solutions

Solution 2

Excelent, That was the perfect solution. I changed the code as shown below and it works excelent.

C++

void Form1::get_TimeStamp(char buffer[])
	{
			
		time_t now = time(NULL);
		tm * ptm = localtime(&now);
		//char buffer[32];
		// Format: Mo, 15.06.2009 20:20:00
		strftime(buffer, MAX_DATE, "[%H:%M:%S]", ptm);

	}

Posted 2-Sep-13 9:21am

Member 7909935

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nv3 · Accepted Answer · 2013-09-02T05:45:00

You cannot return a buffer that is a local (stack) variable of your function. When the function returns the buffer is no longer valid as its memory has been released.

Solution 1: Place the buffer in the calling function and pass a pointer and length to it as parameters. Then let the called function fill the buffer.

Solution 2: Work with string class like std::string or CString, which you can use as return value.