On 2011-10-19 11:05 +0200, Stefano Lattarini wrote: > On Friday 23 September 2011, Nick Bowler wrote: > > Neither bmake nor pmake seem too support $(?F) or $(?D) (both expand > > to be empty in both inference and target rules). And dmake seems to > > differ slightly from POSIX wrt the "D" variants. Quoting IEEE Std > > 1003.1-2004 again: > > > > > The directory part is the path prefix of the file without a > > > trailing slash; for the current directory, the directory part is '.'. > > > > For all the "D" variants, dmake puts a trailing slash contrary to the > > above, and for the current directory expands to the empty string instead > > of "." as required. > > Given this, and the fact that no-one has complained about this automake > limitation so far, I'm oriented at simply leave the situation as is.
The only reason I didn't notice this before is I've been unknowingly running for years without portability warnings enabled. I didn't realize (until now) that they get disabled by "foreign" in: AM_INIT_AUTOMAKE([-Wall -Werror foreign ...]). While it's certainly possible to avoid the use of these macros by doing it in the shell, they're invaluable in non-recursive build systems: probably about half of the suffix rules that I write contain either $(@D) or $(*F) (automake only warns about the latter). Amusingly, of those two variables in the make implementations that I've tested, only $(@D) has portability issues (dmake) -- and it's the one that automake *doesn't* warn about. The dmake issues noted above are pretty minor: I doubt a trailing slash in a directory name would affect many rules, though an empty string instead of "." might. But since these macros are really only useful for working with files *not* in the current working directory, this also seems unlikely to affect many rules (but I guess deserves a note). But yeah, $(?F) and $(?D) are obviously not portable. This is unfortunate, but I haven't actually used these particular macros before. Incidentally, automake also produces similar non-POSIX warnings about $(<), $(*), $(%) and $(?), which are the same as $<, $*, $% and $?, respectively. It also warns about things like $(<:.foo=.bar). Cheers, -- Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/)
