pointer arithmetic for alignment on short or int boundry

[Andy Howell <spam-andy-be-howell-gone@xxxxxxxxxxxxx>]

I need to calculate an address on a short or int boundry. For some 
reason this is not working:

char *a;

a = (a + 1) & ((char*) -2));

Gcc 3.3 on Solaris complains:

error: invalid operands of types `char*' and `
   char*' to binary `operator&'

Why shouldn't I be able to mask off the low bit?

Thanks,

	Andy