Yup,  that's a bug.  I changed your program around to show exactly what the
problem is.  It works correctly with IBM Cset++.  I'll send it to watcom.

 PE>   if (memcmp(&myptr, &def->x, 4) != 0)

This through me for a while --- I think what you really meant was this:

 if(memptr != def->x)


 #include 
 #include 

 typedef struct mystruct
 {
     void * _Seg16 x;
 }MYSTRUCT;

 MYSTRUCT abc;
 MYSTRUCT * _Seg16 def = NULL;
 char     * _Seg16 myptr = NULL;

 long g = 0x12345678L;

 int main(void)
 {
   unsigned *p;
   unsigned v;

   def = &abc;

   def->x = &g;
   myptr = def->x;

   printf(" g = %p, %p, %d\n\n",  &g, (char * _Seg16)&g, g);

   v = (unsigned)((char * _Seg16)&g);
   printf("The following two pointers should contain the thunked\n");
   printf("address of 'g' which is  %04x:%04x\n\n", v >>
16, v & 0xfff);

   p = (unsigned *)&myptr;
   v = *p;
   printf("myptr  = %04x:%04x\n", v >> 16, v & 0xfff);

   p = (unsigned *)&def->x;
   v = *p;
   printf("def->x = %04x:%04x\n", v >> 16, v & 0xfff);

   if (myptr != def->x )
     printf("Error!!\n");

   return (0);
 }




--- Maximus/2 2.01