Error reading character of string C++ - c++

Question

I showed my codes and i have an error reading character of string. Everything is okey in my debugger until the NULL.
*Warning C4715 `String::equas`: not all control paths return a value*
I can not use it because I am using a NULL pointer for the parameter.
How can I solve this problem?
Thanks a lot and have a nice day!
Header:
class String
{
public:
String();
bool empty();
String(char * other_str);
bool equals(const String other_str);
private:
char* m_str;
};
My Codes:
#include "String.hpp"
#include <string>
#include<iostream>
int my_len(const char* p) {
int c = 0;
while (*p != '\0')
{
c++;
*p++;
}
return c;
}
String::String()
:m_str(NULL)
{
}
String::String(char * other_str)
{
}
bool String::empty()
{
return true;
}
bool String::equals(const String other_str)
{
if (m_str == NULL && other_str.m_str == NULL) {
return true;
}
if (m_str == NULL && other_str.m_str != NULL) {
return false;
}
if (m_str != NULL && other_str.m_str == NULL) {
return false;
}
if (m_str != NULL && other_str.m_str != NULL) {
int mystrlen = my_len(m_str);
int myrhslen = my_len(other_str.m_str);
if (mystrlen != myrhslen)
{
return false;
}
else
{
for (int i = 0; i < mystrlen; i++)
{
if (m_str[i] != other_str.m_str[i])
{
return false;
}
else {
return true;
}
}
}
}
}
i will add this codes:
int mylen(const char* p) {
int c = 0;
while (*p != '\0')
{
c++;
*p++;
}
return c;
}
void my_cpy(char dest, const char* src) {
int i = 0;
while (src[i] != '\0') {
dest[i] = src[i];
i++;
}
dest[i] = '\0';
}
char mytrdup(const char *s) {
char* d = (char*)malloc((my_len(s) + 1) * sizeof(char));
if (d == NULL) {
return NULL;
}
else{
my_cpy(d, s);
}
return d;
}

Answer 1

String empty_string2(NULL);
This will invokde the constructor version :
String::String(char* other_str) {}
which does nothing, leaving the m_str pointer dangling/uninitialized. You should change this constructor somehow, either by copying the string and setting the m_str pointer accordingly, or by setting m_str to the same address as the parameter. Either case it depends on what you want to achieve.
Besides, many other problems exist in your code. I notice already this one in you implemented function my_len. you should change *p++ into p++. I wonder how this passed the compilation btw, since the parameter is a const char*.
Finally, the compiler's warning is correct and very clear, although it is not the source of the problem you are facing for the time being.
EDIT: to make a duplicate copy of the string, you can write you constructor like this:
String::String(const char* other_str)
{ m_str = (other_str ? strdup(other_str) : other_str); }
And besides, preferably use null_ptr instead of NULL in your code. Since C++11, this is the standard for null pointers.

Answer 2

I add TEST_TRUE and then that work correctly.