[automake-commit] branch master updated: automake: Support byte compilation in older Emacsen

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karl pushed a commit to branch master
in repository automake.

The following commit(s) were added to refs/heads/master by this push:
     new b87f29742 automake: Support byte compilation in older Emacsen
b87f29742 is described below

commit b87f297426c2d79494b707d0fecddaff2b6eaefd
Author: Karl Berry <address@hidden>
AuthorDate: Sat Jan 4 17:06:40 2020 -0800

    automake: Support byte compilation in older Emacsen
    
    * lib/am/lisp.am (am__emacs_byte_compile_setup) [FIRST]: define
    new make variable, to use byte-compile-dest-file-function if
    available, else byte-compile-dest-file.
    (.el.elc): use it.
    * t/lisp-loadpath.sh: skip test if emacs version is <= 23,
    since their -L ordering is backwards.
    * NEWS: update.
---
 NEWS               |  3 +++
 lib/am/lisp.am     | 21 ++++++++++++++++++++-
 t/lisp-loadpath.sh | 17 +++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index 8c5bf5702..8dc53207b 100644
--- a/NEWS
+++ b/NEWS
@@ -87,6 +87,9 @@ New in ?.?.?:
   - The automake test txinfo-vtexi4.sh no longer fails when localtime
     and UTC cross a day boundary.
 
+  - Emacsen older than version 25, which require use of
+    byte-compile-dest-file, are supported again.
+
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 New in 1.16.1:
diff --git a/lib/am/lisp.am b/lib/am/lisp.am
index 02383eb1e..705181ca1 100644
--- a/lib/am/lisp.am
+++ b/lib/am/lisp.am
@@ -41,10 +41,29 @@ endif %?INSTALL%
          $(EMACS) --batch \
            $(AM_ELCFLAGS) $(ELCFLAGS) \
            $$am__subdir_includes -L $(builddir) -L $(srcdir) \
-           --eval '(setq byte-compile-dest-file-function (lambda (_) "$@"))' \
+           --eval '$(am__emacs_byte_compile_setup)' \
            -f batch-byte-compile '$<'; \
        else :; fi
 
+if %?FIRST%
+## In Automake 1.16, byte compilation was changed to use
+## byte-compile-dest-file-function, but that doesn't exist in Emacs
+## versions earlier than 25, which are still widespread (likely
+## permanently). There's no harm in supporting the older versions, which
+## require defining the byte-compile-file defun, so do so.
+## Otherwise, various of our lisp-related tests fail with the older
+## Emacsen, since they would try to byte-compile into a read-only srcdir.
+##
+## This is used, single-quoted, in the shell sequence above.
+## So use (quote) instead of another single quote in the Lisp.
+##
+am__emacs_byte_compile_setup = \
+  (if (boundp (quote byte-compile-dest-file-function)) \
+    (setq byte-compile-dest-file-function (lambda (_) "$@")) \
+    (defun byte-compile-dest-file (_) "$@") \
+  )
+## Just to be clear: that "$@" above is an Elisp string of the make target.
+endif %?FIRST%
 
 ## ------------ ##
 ## Installing.  ##
diff --git a/t/lisp-loadpath.sh b/t/lisp-loadpath.sh
index 312498845..37bec19d6 100644
--- a/t/lisp-loadpath.sh
+++ b/t/lisp-loadpath.sh
@@ -20,6 +20,23 @@
 required=emacs
 . test-init.sh
 
+# The story here is that at least in Emacs 21, -L foo -L bar ends up
+# with bar before foo in load-path. The invocation in the .el.elc rule
+# in lisp.am correctly uses -L $(builddir) -L $(srcdir), and thus the
+# test below ends up failing. So skip the test on such old Emacs; no
+# need to work around in the code.
+#
+# At least as of Emacs 24, -L foo -L bar preserves command line order,
+# so foo is before bar in load-path, and all is well.
+#
+# Situation with Emacs 22 and 23 is unknown, so play it safe and skip
+# the test for them too.
+#
+emacs_major=$(${EMACS-emacs} --version | sed -e 's/.* //;s/\..*$//;1q')
+if test -z "$emacs_major" || test "$emacs_major" -le 23; then
+  exit 77
+fi
+
 cat >> configure.ac << 'END'
 AM_PATH_LISPDIR
 AC_OUTPUT