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

Your supposition is correct: your strlen is returning the correct value out of sheer luck, because there happens to be a zero on the stack right after your improperly terminated string. It probably helps that the string is 3 bytes, and the compiler is likely aligning stuff on the stack to 4-byte boundaries.

You cannot depend on this. C strings need NUL characters (zeroes) at the end to work correctly. C string handling is messy, and error-prone; there are libraries and APIs that help make it less so… but it's still easy to screw up. :)

In this particular case, your string could be initialized as one of these:

• A: char s2[4] = { 'a','a','a', 0 }; // good if string MUST be 3 chars long
• B: char *s2 = "aaa"; // if you don't need to modify the string after creation
• C: char s2[]="aaa"; // if you DO need to modify the string afterwards

Also note that declarations B and C are 'safer' in the sense that if someone comes along later and changes the string declaration in a way that alters the length, B and C are still correct automatically, whereas A depends on the programmer remembering to change the array size and keeping the explicit null terminator at the end.