#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(void){
    char *ptr = malloc(6);
    const char *name = "MICHI";
    unsigned int i = 0;

    if(ptr){
        strcpy(ptr, name);
        ptr[strlen(ptr)] = '';
    }else{
        return 1;
    }

    while(ptr[i] != ''){
        if((ptr[i] >= 'A') && (ptr[i] <= 'Z')){
            ptr[i] += (unsigned char)32;
        }
        i++;
    }

    printf("Name = %sn",ptr);
    if(ptr){
        free(ptr);
        ptr = NULL;
    }
}

error: conversion to ‘char’ from ‘int’ may alter its value [-Werror=conversion]|

// Both cause the warning
  ptr[i] += (unsigned char) 32;
  ptr[i] = tolower(ptr[i]);

ptr[i] = (char) (ptr[i] + 32);
  ptr[i] = (char) tolower(ptr[i]);

ptr[i] = (char)((int)ptr[i]  + 32);

ptr[i] += (unsigned char)32;

ptr[i] = ptr[i] + 32;

ptr[i] = (unsigned char)(ptr[i] + 32);