Ultrix CC bug?

Bj|rn Larsson bl at infovax.UUCP
Sat Sep 16 01:03:08 AEST 1989


Hello netters,

 yesterday I came upon a strange behaviour in Ultrix 'C'. The following
test program causes cc to complain about the left-hand side of the marked
expression.

	main()
	  {
	  short *p;
	  tst(p);
	  }

	tst (p)
	  short *p;
	  {
	  long	l;
	  l = *((long *) p)++;	/* <<< Here! */
	  }

  In my view,

	p			is a pointer to short,
	(long *) p		is a pointer to long,
	((long *) p)		is also a pointer to long,
	((long *) p)++		increments the above *long* pointer,
	*((long *) p)		is the long pointed to,

	thus

	*((long *) p)++		has the value of the *long* pointed
				to by p, and the *long* pointer is
				set to point to the next long (i.e.
				if sizeof (long)== 2*sizeof(short)
				then p will be incremented by two,
				counted in short's).

  Any objections? I could add that both Turbo C, MicroSoft C, and the
MicroTek C 68000 cross-compiler compile this as I believe 'correctly'.
And this is no problem, I fixed it at another place - but it's inte-
resting to hear what yous C compilers do...


							Bjorn

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