while comma

//-std=c99 -Wall -Wextra -Wpedantic -Wshadow

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

int main (int argc, char **argv){

    char tstStr[]="just testing\n";

    char c;
    char *str;

    str=tstStr;

    while(c=*str++,c)
    {
        printf("%c",c);
    }


    str=tstStr;

    while(*str)
    {
        printf("%c",*str);
        str++;
    }


return 0;
}

/*
just testing
just testing
*/