From: Zack Weinberg <zackw@panix.com>
Subject: [PATCH] Autoconf 2.71 (released last week) makes a few changes 
that broke Automake’s expectations, mostly in the test suite.  This 
patch addresses two of the problems:

 - autoconf now issues a warning if fed a configure script that doesn’t invoke
   both AC_INIT and AC_OUTPUT; this, plus a problem with system-provided
   tools (still under investigation) broke the *build* on macOS; it also
   causes a couple of spurious testsuite failures.

 - AC_PACKAGE_NAME and AC_PACKAGE_VERSION are now defined unconditionally.
   AM_INIT_AUTOMAKE needs to use m4_ifset instead of m4_ifdef to diagnose
   the obsolete use of AC_INIT with fewer than two arguments.  (This change
   is compatible with autoconf 2.69; m4_ifset is much older, and it means
   ‘defined with a non-empty value’.)

* configure.ac: Use both AC_INIT and AC_OUTPUT in test configure scripts.
* t/deprecated-acinit.sh, t/init.sh: Likewise.
* m4/init.m4 (AM_INIT_AUTOMAKE): Use m4_ifset, not m4_ifdef, to detect
  AC_PACKAGE_NAME and/or AC_PACKAGE_VERSION not having a value.
---
 configure.ac           | 9 +++++++--
 m4/init.m4             | 2 +-
 t/deprecated-acinit.sh | 1 +
 t/init.sh              | 1 +
 4 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index 15d3f8e..e3a0df2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -123,7 +123,9 @@ fi
 
 AC_CACHE_CHECK([whether autoconf works], [am_cv_autoconf_works],
 [mkdir conftest
-echo 'AC''_INIT' > conftest/conftest.ac
+printf '%s\n' > conftest/conftest.ac \
+  'AC''_INIT([smoke-test], [1])' \
+  'AC''_OUTPUT'
 if AM_RUN_LOG([cd conftest && $am_AUTOCONF -o /dev/null conftest.ac]);
 then
   am_cv_autoconf_works=yes
@@ -139,7 +141,10 @@ fi
 AC_CACHE_CHECK([whether autoconf is recent enough], [am_cv_autoconf_version],
 [mkdir conftest
 dnl Creative quoting required to avoid spurious expansion of AC_PREREQ macro
-echo 'AC'"_PREREQ([[$required_autoconf_version]])" > conftest/conftest.ac
+printf '%s\n' > conftest/conftest.ac \
+  'AC'"_PREREQ([[$required_autoconf_version]])" \
+  'AC''_INIT([smoke-test], [1])' \
+  'AC''_OUTPUT'
 if AM_RUN_LOG([cd conftest && $am_AUTOCONF -o /dev/null conftest.ac]);
 then
   am_cv_autoconf_version=yes
diff --git a/m4/init.m4 b/m4/init.m4
index ba73676..339a167 100644
--- a/m4/init.m4
+++ b/m4/init.m4
@@ -64,7 +64,7 @@ m4_ifval([$3], [_AM_SET_OPTION([no-define])])dnl
 [_AM_SET_OPTIONS([$1])dnl
 dnl Diagnose old-style AC_INIT with new-style AM_AUTOMAKE_INIT.
 m4_if(
-  m4_ifdef([AC_PACKAGE_NAME], [ok]):m4_ifdef([AC_PACKAGE_VERSION], [ok]),
+  m4_ifset([AC_PACKAGE_NAME], [ok]):m4_ifset([AC_PACKAGE_VERSION], [ok]),
   [ok:ok],,
   [m4_fatal([AC_INIT should be called with package and version arguments])])dnl
  AC_SUBST([PACKAGE], ['AC_PACKAGE_TARNAME'])dnl
diff --git a/t/deprecated-acinit.sh b/t/deprecated-acinit.sh
index 21614ba..f393d65 100644
--- a/t/deprecated-acinit.sh
+++ b/t/deprecated-acinit.sh
@@ -35,6 +35,7 @@ for ac_init in AC_INIT 'AC_INIT([Makefile.am])'; do
         $ac_init
         $am_init_automake
         AC_CONFIG_FILES([Makefile])
+        AC_OUTPUT
 END
     cat configure.ac # For debugging.
     $ACLOCAL 2>stderr && { cat stderr >&2; exit 1; }
diff --git a/t/init.sh b/t/init.sh
index c6f6d64..df138a0 100644
--- a/t/init.sh
+++ b/t/init.sh
@@ -25,6 +25,7 @@ for ac_init_args in '' '([x])'; do
     unindent >configure.ac <<END
       AC_INIT$ac_init_args
       AM_INIT_AUTOMAKE$am_init_args
+      AC_OUTPUT
 END
     cat configure.ac # For debugging.
     # The error message should mention AC_INIT, not AC_PACKAGE_VERSION.
-- 
2.26.0