dist: fix bug#18286 "distcheck fails to detect missing files"

BTW, this issue had been already reported in the past:
http://lists.gnu.org/archive/html/automake/2006-09/msg00008.html
http://lists.gnu.org/archive/html/automake/2013-01/msg00049.html

"make distcheck" could sometimes fail to detect missing files in the
distribution tarball, especially in those cases where both the generated
files and their dependencies are explicitly in $(srcdir).  An important
example of this are *generated* makefile fragments included at Automake
time in Makefile.am.  A basic example:

    # -*- Makefile.am -*-

    $(srcdir)/fragment.am: $(srcdir)/data.txt $(srcdir)/preproc.sh
        cd $(srcdir) && $(SHELL) preproc.sh <data.txt >fragment.am

    include $(srcdir)/fragment.am

    ...

If the use forgot to add data.txt and/or preproc.sh in the distribution
tarball, "make distcheck" would have erroneously succeeded!

The reason is that, while $(srcdir)/data.txt does not exist, make also
looks in $(srcdir)/$(srcdir)/data.txt, and in the distcheck-issued
VPATH build where $(srcdir) is '..', that file exists, as it is
part of the original development directory.

* t/distdir.am (distcheck): Adjust to have the build directory be
'$(distdir)/_build/sub' rather than just '$(distdir)/_build'.  Thanks
Nicola Fontana for the suggestion.
* t/distcheck-pr18286.sh: Enhance and tighten a little.
* t/list-of-tests.mk (XFAIL_TESTS): Remove 't/distcheck-pr18286.sh',
as it's now passing.
* t/subdir-am-cond.sh: Adjust to avoid a fully spurious failure due
to the new distcheck semantics.
* t/subdir-ac-subst.sh: Likewise.
* t/dejagnu-relative-srcdir.sh: Likewise.
* t/txinfo-builddir.sh: Likewise.
* NEWS: Update.

Helped-by: Nicola Fontana <ntd@entidi.it>
Helped-by: Peter Johansson <trojkan@gmail.com>
Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

1 files changed, 9 insertions, 5 deletions

diff --git a/lib/am/distdir.am b/lib/am/distdir.am
index a8ad63cef..6d9d42f28 100644
--- a/lib/am/distdir.am
+++ b/lib/am/distdir.am
@@ -1,5 +1,5 @@
 ## automake - create Makefile.in from Makefile.am
-## Copyright (C) 2001-2013 Free Software Foundation, Inc.
+## Copyright (C) 2001-2014 Free Software Foundation, Inc.
 
 ## This program is free software; you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -430,7 +430,7 @@ distcheck: dist
 ## can make our new subdirs.
 	chmod -R a-w $(distdir)
 	chmod u+w $(distdir)
-	mkdir $(distdir)/_build $(distdir)/_inst
+	mkdir $(distdir)/_build $(distdir)/_build/sub $(distdir)/_inst
 ## Undo the write access.
 	chmod a-w $(distdir)
 ## With GNU make, the following command will be executed even with "make -n",
@@ -451,8 +451,12 @@ distcheck: dist
 ## Parallel BSD make may not start a new shell for each command in a recipe,
 ## so be sure to 'cd' back to the original directory after this.
 	  && am__cwd=`pwd` \
-	  && $(am__cd) $(distdir)/_build \
-	  && ../configure \
+## If we merely used '$(distdir)/_build' here, "make distcheck" could
+## sometimes fail to detect missing files in the distribution tarball,
+## especially in those cases where both the generated files and their
+## dependencies are explicitly in $(srcdir).  See automake bug#18286.
+	  && $(am__cd) $(distdir)/_build/sub \
+	  && ../../configure \
 ?GETTEXT?	    --with-included-gettext \
 ## Additional flags for configure.
 	    $(AM_DISTCHECK_CONFIGURE_FLAGS) \
@@ -461,7 +465,7 @@ distcheck: dist
 ## and --prefix values, so don't allow them to be overridden by the user or
 ## the developer.  That used to be allowed, and caused issues in practice
 ## (in corner-case usages); see automake bug#14991.
-	    --srcdir=.. --prefix="$$dc_install_base" \
+	    --srcdir=../.. --prefix="$$dc_install_base" \
 	  && $(MAKE) $(AM_MAKEFLAGS) \
 	  && $(MAKE) $(AM_MAKEFLAGS) dvi \
 	  && $(MAKE) $(AM_MAKEFLAGS) check \