+mkdir sub
+cat > sub/Makefile.am << 'END'
+dream_SOURCES = generic/b.c more/r.y
+bin_PROGRAMS = dream
+END
+
+AUTOMAKE_fails
+grep "^Makefile\.am:3:.*'generic/a\.c'.* in a subdirectory" stderr
+grep "^Makefile\.am:[34]:.*'another/z\.cxx'.* in a subdirectory" stderr
+grep "^sub/Makefile\.am:1:.*'generic/b\.c'.* in a subdirectory" stderr
+grep "option 'subdir-objects' is disabled" stderr
+# Verbose tips should be given, but not too many times.
+for msg in \
+ "possible forward-incompatibility" \
+ "advi[sc]e.* 'subdir-objects' option throughout" \
+ "unconditionally.* object file.* same subdirectory" \
+; do
+ test $(grep -c "$msg" stderr) -eq 1
+done
+
+# Guard against stupid typos.
+grep 'subdir-object([^s]|$)' stderr && exit 1
+
+$AUTOMAKE -Wno-unsupported
+
+echo AUTOMAKE_OPTIONS = subdir-objects >> Makefile.am
+AUTOMAKE_fails
+grep "^Makefile\.am" stderr && exit 1
+grep "^sub/Makefile\.am:.*'generic/b\.c'.* in a subdirectory" stderr
+grep "option 'subdir-objects' is disabled" stderr
+
+sed 's/^AM_INIT_AUTOMAKE/&([subdir-objects])/' configure.ac > configure.tmp
+mv -f configure.tmp configure.ac
+$ACLOCAL --force
+$AUTOMAKE
+
+rm -f compile