port elisp-compilation support to emacs-23.1 and newer

In May of 2017, emacs.master support for using the long-deprecated
byte-compile-dest-file function was removed, and that removal broke
automake's elisp-compiling rule for any .el file not in the current
directory.  In emacs-23.1 (July 2009) byte-compile-dest-file-function
became the recommended way to adjust the byte-compiler's destination.
The removed functionality has been restored for Emacs-26, albeit with
dissuasive diagnostics warning about the imminent removal of this
functionality.  It will be removed in Emacs-27.
* lib/am/lisp.am (.el.elc): Use byte-compile-dest-file-function, rather
than byte-compile-dest-file.  Also, use "-f batch-byte-compile '$<'"
rather than open-coding it, as suggested by Glenn Morris.
* t/lisp-readonly-srcdir.sh: New file, to test for the above.
* t/list-of-tests.mk (handwritten_TESTS): Add it.
* NEWS (Bugs fixed): Mention this problem.

4 files changed, 55 insertions, 3 deletions

diff --git a/NEWS b/NEWS
index 6d8b9d248..7d52aeb93 100644
--- a/NEWS
+++ b/NEWS
@@ -124,6 +124,11 @@ New in ?.?.?:
   - The time printed by 'mdate-sh' is now using the UTC time zone to support
     the reproducible build effort.  (automake bug#20314)
 
+  - The elisp byte-compilation rule now uses byte-compile-dest-file-function,
+    rather than byte-compile-dest-file, which was obsoleted in 2009. We expect
+    that Emacs-26 will continue to support the old function, but will complain
+    loudly, and that Emacs-27 will remove support for it altogether.
+
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 New in 1.15.1:
diff --git a/lib/am/lisp.am b/lib/am/lisp.am
index 881bf3457..91a0e0516 100644
--- a/lib/am/lisp.am
+++ b/lib/am/lisp.am
@@ -30,7 +30,7 @@ endif %?INSTALL%
 ## The destination file is normally determined by appending "c" to the
 ## input (which would erronously put it in $(srcdir) in VPATH builds),
 ## so we override that, too.
-	if test "$(EMACS)" != "no"; then \
+	if test '$(EMACS)' != no; then \
 	  am__dir=. am__subdir_includes=''; \
 	  case $@ in */*) \
 	    am__dir=`echo '$@' | sed 's,/[^/]*$$,,'`; \
@@ -41,8 +41,8 @@ endif %?INSTALL%
 	  $(EMACS) --batch \
 	    $(AM_ELCFLAGS) $(ELCFLAGS) \
 	    $$am__subdir_includes -L $(builddir) -L $(srcdir) \
-	    --eval "(defun byte-compile-dest-file (f) \"$@\")" \
-	    --eval "(unless (byte-compile-file \"$<\") (kill-emacs 1))"; \
+	    --eval '(setq byte-compile-dest-file-function (lambda (_) "$@"))' \
+	    -f batch-byte-compile '$<'; \
 	else :; fi
 
 
diff --git a/t/lisp-readonly-srcdir.sh b/t/lisp-readonly-srcdir.sh
new file mode 100644
index 000000000..38b866404
--- /dev/null
+++ b/t/lisp-readonly-srcdir.sh
@@ -0,0 +1,46 @@
+#! /bin/sh
+# Copyright (C) 2017 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
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+# Ensure that building elisp from a read-only srcdir works.
+
+required=emacs
+. test-init.sh
+
+cat > Makefile.am << 'EOF'
+lisp_LISP = am-one.el
+EOF
+
+cat >> configure.ac << 'EOF'
+AM_PATH_LISPDIR
+AC_OUTPUT
+EOF
+
+echo > am-one.el
+
+$ACLOCAL
+$AUTOCONF
+$AUTOMAKE --add-missing
+
+mkdir sub
+chmod a=rx .
+
+cd sub
+../configure
+$MAKE
+
+test -f am-one.elc
+
+:
diff --git a/t/list-of-tests.mk b/t/list-of-tests.mk
index 61ad5b4e8..fde769971 100644
--- a/t/list-of-tests.mk
+++ b/t/list-of-tests.mk
@@ -656,6 +656,7 @@ t/lisp5.sh \
 t/lisp6.sh \
 t/lisp7.sh \
 t/lisp8.sh \
+t/lisp-readonly-srcdir.sh \
 t/lisp-loadpath.sh \
 t/lisp-subdir.sh \
 t/lisp-subdir2.sh \