Bad permissions for mapped region [duplicate]

Answer 1

You are passing a constant string to your function.

String literals are of type char [N + 1] (where N is the length of the array) in C, but modifying them results in undefined behavior. Your compiler should have already issued a warning at that point.

If you wish to modify it then you have to create a copy:

char str[] = "BeforeSunrise";
char* rev2=reverseInPlace(str);

Answer 2

It's because you try to modify a string literal, which is a constant array, i.e. it's read-only.