What is the issue with this reverse array code in c++?

The program compile fine, but crashes when is running and shows this : Process terminated with status -1073741819

void reverse(char *str){

    char * end1 = str;
    char tmp = 'c';
    if(str){
        while(*end1){
            ++end1;
        }
        --end1;

        while(str<end1){
            tmp=*str;
            *str=*end1;
            *end1=tmp;
            str++;
            end1--;
        }
    }
}

Any idea ?