digitp is defined in several places in the GnuPG codebase. three of these
definitions treat p as a char*, but one of them treats p as a char. This should
probably be cleaned up:

common/simple-pwquery.c:#define digitp(p) (*(p) >= '0' && *(p) <= '9')
common/util.h:#define digitp(p) (*(p) >= '0' && *(p) <= '9')
kbx/keybox-defs.h:#define digitp(p) (*(p) >= '0' && *(p) <= '9')
tools/ccidmon.c:#define digitp(p) ((p) >= '0' && (p) <= '9')