automake-1.16: Subdirectories with AM_CONDITIONAL
7.2.2 Subdirectories with ‘AM_CONDITIONAL’
------------------------------------------
‘configure’ should output the ‘Makefile’ for each directory and define a
condition into which ‘opt/’ should be built.
...
AM_CONDITIONAL([COND_OPT], [test "$want_opt" = yes])
AC_CONFIG_FILES([Makefile src/Makefile opt/Makefile])
...
Then ‘SUBDIRS’ can be defined in the top-level ‘Makefile.am’ as
follows.
if COND_OPT
MAYBE_OPT = opt
endif
SUBDIRS = src $(MAYBE_OPT)
As you can see, running ‘make’ will rightly recurse into ‘src/’ and
maybe ‘opt/’.
As you can’t see, running ‘make dist’ will recurse into both ‘src/’
and ‘opt/’ directories because ‘make dist’, unlike ‘make all’, doesn’t
use the ‘SUBDIRS’ variable. It uses the ‘DIST_SUBDIRS’ variable.
In this case Automake will define ‘DIST_SUBDIRS = src opt’
automatically because it knows that ‘MAYBE_OPT’ can contain ‘opt’ in
some condition.
Info Catalog
automake-1.16: SUBDIRS vs DIST_SUBDIRS
automake-1.16: Conditional Subdirectories
automake-1.16: Subdirectories with AC_SUBST