C compiler incompatibility

[Mike Cuddy]

I'm writing macros to deal with linked lists. (circular) and I'm having a spot
of trouble with xlc ( this works fine on a SUN!):


------- cut here -------
typedef struct cll_f {
    struct list *next;
    struct list *prev;
} cll_t;

struct foo {
    cll_t  list;

    int a, b, c;
    /* ... more stuff ... */
};

#define CLL_FOREACH(head,p) \
	for((cll_t *)(p) = (head)->list.next ; \
	    (p) != (head) ; (cll_t *)(p) = (p)->list.next)


void traverse(list)
struct foo *list;
{
    struct foo *p;
    CLL_FOREACH(list,p) {

    /* ... output data ... */

    }
}

------ cut here -------
% cc foo.c
       23 |     for((cll_t *)(p) = (list)->list.next ; (p) != (list) ; (cll_t 
            ........a..................................................b......
a - 1506-025: (S) Operand must be a modifiable lvalue.
b - 1506-025: (S) Operand must be a modifiable lvalue.
            *)(p) = (p)->list.next) {

------ extracted from my xlc.cfg: -------

* standard c compiler aliased as cc
cc:     use        = DEFLT
        crt        = /lib/crt0.o
        mcrt       = /lib/mcrt0.o
        gcrt       = /lib/gcrt0.o
        libraries  = -lc
        proflibs   = -L/lib/profiled,-L/usr/lib/profiled
        options    = -H512,-T512, -qlanglvl=extended, -qnoro


* common definitions
DEFLT:  xlc        = /usr/lpp/xlc/bin/xlcentry
        as         = /bin/as
        ld         = /bin/ld
        options    = -D_IBMR2,-D_AIX,-bhalt:4
        ldopt      = "b:o:e:u:R:H:Y:Z:L:T:A:V:k:j:"

--Mike Cuddy
"...He's a UNIX hack and he's okay, he works all night and he sleeps all day..."