I’m using automake 1.15.1 on Fedora 28.
I changed my AM_INIT_AUTOMAKE() to include subdir-objects.
As soon as I did this, I started seeing failures like:
make[2]: Entering directory '/home/philipp/git/snt/libntp'
Makefile:902: warning: overriding recipe for target
'../lib/isc/pthreads/.dirstamp'
Makefile:802: warning: ignoring old recipe for target
'../lib/isc/pthreads/.dirstamp'
Makefile:905: warning: overriding recipe for target
'../lib/isc/pthreads/.deps/.dirstamp'
Makefile:805: warning: ignoring old recipe for target
'../lib/isc/pthreads/.deps/.dirstamp'
Makefile:964: ../lib/isc/unix/.deps/time.Po: No such file or directory
make[2]: *** No rule to make target '../lib/isc/unix/.deps/time.Po'. Stop.
make[2]: Leaving directory '/home/philipp/git/snt/libntp'
After some head-scratching, I noticed:
$ find . -name '$*' -print
./sntp/tests/$(top_builddir)
./tests/ntpd/$(srcdir)
./libntp/$(srcdir)
$
and root-caused this to here:
# Extract the definition of DEPDIR, am__include, and am__quote
# from the Makefile without running 'make'.
DEPDIR=`sed -n 's/^DEPDIR = //p' < "$mf"`
test -z "$DEPDIR" && continue
am__include=`sed -n 's/^am__include = //p' < "$mf"`
test -z "$am__include" && continue
am__quote=`sed -n 's/^am__quote = //p' < "$mf"`
# Find all dependency output files, they are included files with
# $(DEPDIR) in their names. We invoke sed twice because it is the
# simplest approach to changing $(DEPDIR) to its actual value in the
# expansion.
for file in `sed -n "
s/^$am__include $am__quote\(.*(DEPDIR).*\)$am__quote"'$/\1/p' <"$mf" | \
sed -e 's/\$(DEPDIR)/'"$DEPDIR"'/g'`; do
# Make sure the directory exists.
test -f "$dirpart/$file" && continue
fdir=`$as_dirname -- "$file" ||
…
as_dir=$dirpart/$fdir; as_fn_mkdir_p
# echo "creating $dirpart/$file"
echo '# dummy' > "$dirpart/$file"
done
Problem is, what happens if the line you’ve read looks like:
include $(srcdir)/../lib/isc/unix/$(DEPDIR)/time.Po
after mangling that, we end up with
file=$(srcdir)/../lib/isc/unix/.deps/time.Po which is obviously wrong.
Yes, $(DEPDIR) needs to be substituted out… but so does every other variable
potentially, including $(srcdir) …
Either subdir-objects should handle ALL possible expansions (might require some
hackery and recursively calling Makefile on each line to do expansions)… or
configure should make sure that $file doesn’t match /\$(.*)/ indicating that it
contains unexpanded variables… and maybe suggest using @variable@ substitutions
instead if possible.
If you want to reproduce this yourselves, grab the ntp-4.8.2p11 tarball and
change configure.ac and sntp/configure.ac to use AM_INIT_AUTOMAKE([…
subdir-objects …]) instead.
Run:
./bootstrap
./configure --with-crypto --with-threads --disable-silent-rules
--disable-local-libevent
and you’ll see the broken behavior.
Thanks,
-Philip
