String problems - strings seem to join?

This is a discussion on String problems - strings seem to join? within the C++ Programming forums, part of the General Programming Boards category; I'm having some trouble to do with strings, with a function I've written. First, at the top of the program, ...

  1. #1
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    Jan 2007
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    String problems - strings seem to join?

    I'm having some trouble to do with strings, with a function I've written.

    First, at the top of the program, outside of main, I've declared the following global strings, to hold the time, and the date:

    Code:
    char Date[11];
    char Time[9];
    The variables are given data during this function:

    Code:
    /* Load time */
    /* Loads the time and date settings into the global Time and Date variables */
    
    int LoadTime()
    {
    	cout << "Loading time and date...\n";
    
    	time_t TimeObject;
    	tm * TimePointer;
    
    	time(&TimeObject);
    	TimePointer = gmtime(&TimeObject);
    	char Symbols[3] = "-:\0";
    
    	string MyTimeString = asctime(TimePointer);
    	
    	Date[0] = MyTimeString[8];
    	Date[1] = MyTimeString[9];
    	Date[2] = Symbols[0];
    	Date[3] = MyTimeString[4];
    	Date[4] = MyTimeString[5];
    	Date[5] = MyTimeString[6];
    	Date[6] = Symbols[0];
    	Date[7] = MyTimeString[20];
    	Date[8] = MyTimeString[21];
    	Date[9] = MyTimeString[22];
    	Date[10] = MyTimeString[23];
    	Date[11] = Symbols[2];
    
    	Time[0] = MyTimeString[11];
    	Time[1] = MyTimeString[12];
    	Time[2] = MyTimeString[13];
    	Time[3] = MyTimeString[14];
    	Time[4] = MyTimeString[15];
    	Time[5] = MyTimeString[16];
    	Time[6] = MyTimeString[17];
    	Time[7] = MyTimeString[18];
    	Time[8] = MyTimeString[19];
    	Time[9] = Symbols[2];
    	
    	cout << Date << "\n";
    	
    	return 0;
    }
    The problem is, when Date is printed onto the console, the contents of time also appear after date too! I thought that the string should have been terminated by the \0 escape code.

    Does any kind people have some insight into this strange behaivour?

  2. #2
    Cat without Hat CornedBee's Avatar
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    Apr 2003
    Posts
    8,893
    You didn't actually provide space for the '\0' terminator. Date contains space for 11 characters (indices 0-10), but you assign to the twelth (index 11).

    As it happens on your platform, Date and Time are directly adjacent in memory, so Time[0] is the same memory location as (the invalid) Date[11]. In other words, the assignment to Time[0] overwrites the terminator you gave Date.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

  3. #3
    Registered User
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    Jan 2007
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    Ah, excelent! Such a simple problem, sometimes it takes another pair of eyes to spot these sort of things. Thankyou so much.

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