Implement Arbitrary for CString

[clarfonthey]

Would be nice to have. String's impl isn't quite the same.

[BurntSushi]

PR's are welcome for this.

[ThomasdenH]

What would be the ideal implementation here? Using the String implementation with a null-character or random non-null bytes terminated by a null character? Or some combination of the two?

For example, based on a random variable, either add a valid UTF-8 character to the string or a random non-null byte. Finally, end the string with '\0'.

[BurntSushi]

Yeah, I think we probably want a mix. I believe the Arbitrary impl for String has some smarts to it, and it would be nice to reuse that. While perhaps not optimal, I think one possible implementation of this would be:

• Flip a coin. If heads, call Vec<u8>::arbitrary() and strip all NUL bytes from the result (or replace them with random non-NUL bytes).
• If tails, call String::arbitrary() and strip all NUL bytes from the result (or replace them with random non-NUL UTF-8 encoded Unicode scalar values).