how to make a not null-terminated c string?

Question

i am wondering :char *cs = .....;what will happen to strlen() and printf(\"%s\",cs) if cs point to memory block which is huge but with no \'\\0\' in it? i write these lines

Answer 1

What happens is that strlen keeps going, reading memory values until it eventually gets to a null. it then assumes that is the terminator and returns the length that could be massively large. If you're using strlen in an environment that expects C-strings to be used, you could then copy this huge buffer of data into another one that is just not big enough - causing buffer overrun problems, or at best, you could copy a large amount of garbage data into your buffer.

Copying a non-null terminated C string into a std:string will do this. If you then decide that you know this string is only 3 characters long and discard the rest, you will still have a massively long std:string that contains the first 3 good characters and then a load of wastage. That's inefficient.

The moral is, if you're using the CRT functions to operator on C strings, they must be null-terminated. Its no different to any other API, you must follow the rules that API sets down for correct usage.

Of course, there is no reason you cannot use the CRT functions if you always use the specific-length versions (eg strncpy) but you will have to limit yourself to just those, always, and manually keep track of the correct lengths.