char array contains absurd characters

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C++

void eatSpaces(const char arr[])
{
	char* str = new char[];
	size_t strPosition{}, arrPosition{};
	while (arr[arrPosition] != '\0')
	{
		if (arr[arrPosition] != ' ')
			str[strPosition++] = arr[arrPosition];

		arrPosition++;
	}
	cout << str << endl;
}

void main()
{
	char str[]{"hello world"};
	eatSpaces(str);
}

every time I run this program it shows 2 absurd characters at the end of the str[]. They are like some randomly generated characters..
For the first time, it displays "helloworldφ8"
and then, "helloworld.C"
after that, "helloworld├b"

It isn't same always.. I just want to know why this happens.. Not another way to remove spaces without this problem.. Thanks..

Posted 25-May-14 0:05am

Mark

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Richard MacCutchan · Accepted Answer · 2014-05-25T02:55:00

Solution 3

The problem is that you copy the characters from arr to str, and stop (correctly) when the null character is reached. However, you forget to add a null character at the end of the newly created string. It should be:

C++

while (arr[arrPosition] != '\0')
{
    if (arr[arrPosition] != ' ')
        str[strPosition++] = arr[arrPosition];

    arrPosition++;
}
str[strPosition] = '\0';  // null terminate the new string

By the way, what compiler are you using, as this will not compile under Microsoft's C++ compiler, owing to the strange syntax on some statments?

Posted 25-May-14 2:55am

Richard MacCutchan

Comments

Mark 25-May-14 9:03am

Im using the compiler that came with visual studio 2013

Richard MacCutchan 25-May-14 9:30am

Thanks, I must learn the new syntax.

You also have a potential bug in this code. When you create the second array with the line
char* str = new char[];
it returns you a pointer to a default sized buffer. According to my tests this buffer is 64 bytes (characters) long. So if you write more than that number of characters into it you will corrupt the heap and see strange results.

Mark 25-May-14 9:49am

oh.. Thanks. Didn't know that..

Richard MacCutchan 25-May-14 9:51am

Nor did I, and the documentation is not very clear.