Why is there an exception?

[LarryChen]

Here is the code,

bool isRotational(char* s1, char* s2)
{
	int len = strlen(s1);
	char* s = new char[2 * len + 1];
	char* p = s1;
	char* q = s;

	while (*p)
	{
		*s++ = *p++;
	}

	p = s1;

	while (*p)
	{
		*s++ = *p++;
	}
	
	*s = '\0';

	int len2 = strlen(s2);
	int j;
	for (int i = 0; i<2 * len - len2 + 1; ++i)	
	{
		for (j = 0; j < len2 && q[i + j] == s2[j]; ++j);

		if (j == len2)
			return true;
	}

	delete[] s;
	return false;
}

I randomly found that the exception is caused by the statement delete[] s. But when I debug this code, the debugger won't point to the statement delete[] s at all. So I am just wondering how'd I find out the exception is caused by that? Secondly why is there an exception in the code that looks innocent? Thanks!

[Philip Nicoletti]

delete []  s;

What is "s" pointing to ? many times you increment the value of s.

[LarryChen]

delete []  s;

What is "s" pointing to ? many times you increment the value of s.

I got it. Thanks. How am I able to debug such error? It seems the debugger won't point to the correct statement when such exception is thrown.

[laserlight]

How am I able to debug such error? It seems the debugger won't point to the correct statement when such exception is thrown.

Read Stroustrup's answer to the FAQ How do I deal with memory leaks? The executive summary: use a std::string or a container like std::vector instead of doing manual memory management.