Thanks Stepan. I'm going to go with your latter suggestion, since it doesn't require modifying all the other Makefile.am. This seems like a rather arbitrary limitation of automake though. Is there any reason why the append operator shouldn't treat an undefined variable as empty?
Cheers, Shaun > 2) Or the extra.am starts with > CLEANFILES = > and each caller takes care not to touch it before the include. > So the former snippet will become > > bin_PROGRAMS = hello > include $(top_srcdir)/extra.am > CLEANFILES += something > > HTH, > Stepan Kasal