C++ reverse string [closed] - c++

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Good day,
Please can someone assist? I am trying to reverse a member that is a pointer array.
string::string(char *c)
{
int i =0;
while ((c[i] != '\0'))
{
i++;
}
_lenght= i;
_aString=*&c;
}
void string::reverse() //Requirements specify to have this argument
{
for(int i=0; i<_lenght/2; i++)
{
std::swap(_aString[i], _aString[_lenght-i-1]);
}
}
I get a runtime error on this.
This is my main function
int main(){
string a;
std::cout << "a is " << a << "\n";
string b("12345");
string c("12345",3);
std::cout << "c is " << c << "\n";
c = a;
a = b;
std::cout << "a is " << a << "\n";
b.reverse();
std::cout << "a is " << a << "\n";
return 0;
}
Error I'm getting is
Unhandled exception at 0x00fd6710 in UnisaLesson1.exe: 0xC0000005: Access violation writing location 0x00fdfd08.
Sorry, I'm still a newb.

Answer 1

The problem is
_aString=*&c;
which is a weird way of writing
_aString=c;
so that _aString is simply pointing to whatever the function argument was; this class doesn't manage a the memory for a string (as std::string does), but refers to an external string managed elsewhere.
In your test case, that string is a string literal - which isn't modifiable. So attempting to modify it, as reverse does, gives undefined behaviour; if you're lucky, an access violation; if you're unlucky, data corruption or some other unwanted runtime behaviour.
If your class is supposed to manage the memory, then it will need to allocate it in the constructor. Assuming this assignment is an exercise in memory management (otherwise, just use std::string), you'd want something like
_aString = new char[_lenght];
std::copy(c, c+_lenght, _aString);
and don't forget the Rule of Three:
a destructor to release the memory with delete [] _aString
copy constructor, either deleted to prevent copying, or implemented to allocate a new buffer;
copy-assignment operator, either deleted to prevent copying, or implemented to copy into the existing buffer after resizing if necessary.
You might also consider fixing the spelling of _lenght to _length.