立秋散分，顺便问个写法有关问题

do
{
    ....
} while(0);

//为什么要这么写？这种形式好在哪？

#define FREE1(p) {if (p) free (p);}
void main()
{   

    int *p=(int*)malloc(10); 
    int i=1;
    if (i>0)
        FREE1(p)
    else
    printf("expression was false.n") ;

}