Make use of GCC's attribute __alloc_size__. * lib/xalloc.h (ATTRIBUTE_ALLOC_SIZE): New macro. (xmalloc, xzalloc, xcalloc, xrealloc, xmemdup, xnmalloc, xnrealloc, xcharalloc): Declare with ATTRIBUTE_ALLOC_SIZE. * lib/eealloc.h (eemalloc, eerealloc): Declare with attribute __alloc_size__. * lib/pagealign_alloc.h (pagealign_alloc, pagealign_xalloc): Likewise. Suggested by Jim Meyering.