kc3-lang/automake

2012-06-10T23:08:07

subdirs: unify rules for "cleaning" and "normal" recursive targets Before this change, the recursive invocation of cleaning targets in the $(SUBDIRS) where done in inverse order, i.e., starting from the last $(SUBDIRS) entry and proceeding towards the first. According to the code comments, this was done ... ... in an attempt to alleviate a problem that can happen when dependencies are enabled. In this case, the .P file in one directory can depend on some automatically generated header in an earlier directory. Since the dependencies are required before any target is examined, make bombs. But this comment does not apply anymore to the current implementation of automatic dependency tracking: the '.Po' and '.Plo' files does not depend on any C header or source file, ever! So it seems that the distinction between "normal" and "cleaning" recursive targets is a stale leftover of an older implementation of the automatic dependency tracking. In fact, the Automake History manual seems to confirm this suspect; the section "First Take on Dependency Tracking" reads: Because each .P file was a dependency of Makefile, this meant that dependency tracking was done eagerly by make. For instance, "make clean" would cause all the dependency files to be updated, and then immediately removed. This eagerness also caused problems with some configurations; if a certain source file could not be compiled on a given architecture for some reason, dependency tracking would fail, aborting the entire build. and the following section "Dependencies As Side Effects" reads: In this approach, the .P files were included using the -include command, which let us create these files lazily. This avoided the "make clean" problem. So the distinction between "normal" and "cleaning" recursive targets has likely been obsolete since by then already. We can thus remove such distinction, thus reducing some complications and duplication in our rules. Doing so, the whole testsuite still passes (both with GCC and Sun C 5.9), even the test 'c-demo.sh', which, among the other things, exercise the setup described in the obsolete code comment referenced above. Finally, note that we still keep '$(RECURSIVE_CLEAN_TARGETS)' and '$(RECURSIVE_TARGETS)' as two distinct variables, to ensure a better backward-compatibility for any user-defined rules that happen to use those variables. * NEWS: Update. * lib/am/subdirs.am ($(RECURSIVE_CLEAN_TARGETS), $(CLEAN_TARGETS)): Merge their recipes. * t/subdir-distclean.sh: New test, check that "./configure && make && make distclean" is actually a no-op, even when conditional SUBDIRS are involved. * t/list-of-tests.mk: Add it. Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>