如何将字符指针转换为小写

#include <stdio.h>
#include <ctype.h>

void toLowerCase(char* str) {
    if (str == NULL) {
        return;
    }
    
    while (*str != '\0') {
        *str = tolower(*str);
        str++;
    }
}

int main() {
    char str[] = "Hello World!";
    printf("Before conversion: %s\n", str);
    
    toLowerCase(str);
    
    printf("After conversion: %s\n", str);
    
    return 0;
}

Before conversion: Hello World!
After conversion: hello world!