Собственная функция strlen не вызывается

#include "pch.h"
#include <iostream>
using namespace std;
 
unsigned strlen(const char *str)
{
    unsigned x = 0;
    while (str[x] != 0) x++;
    return x;
}
 
int main()
{
    // Test 1
    const char* str1 = "How do you do";
    if (strlen(str1) == 13)
        cout << "Test 1 passed" << endl;
    else cout << "Test 1 failed" << endl;
    // Test 2
    const char* str2 = "";
    if (strlen(str2) == 0)
        std::cout << "Test 2 passed" << std::endl;
    else std::cout << "Test 2 failed" << std::endl;
    // Test 3
    const char* str3 = "This is stepik.org";
    if (strlen(str3) == 18)
        std::cout << "Test 3 passed" << std::endl;
    else std::cout << "Test 3 failed" << std::endl;
    const char* str4 = "Russian Federation";
    if (strlen(str4) == 18)
        std::cout << "Test 4 passed" << std::endl;
    else std::cout << "Test 4 failed" << std::endl;
    const char* str5 = "Russia";
    if (strlen(str5) == 6)
        std::cout << "Test 5 passed" << std::endl;
    else std::cout << "Test 5 failed" << std::endl;
}

inline
unsigned str_len(const char *str)
{
unsigned x = 0;
while (str[x] != 0) x++;
return x;
}