rm: handle -f w/no arguments gracefully

Fixes automake bug https://bugs.gnu.org/10828.

Delete the configure check that would abort if `rm -f` does not work,
and delete the plans to make this a hard requirement in the future.

Instead, test to see if `rm -f` fails w/out arguments.  If it does,
define am__rm_f such that it always passes at least the "" argument
when deleting files.  If it doesn't fail, then we can omit the "".

Then go through lib/am/ and update places where we use the pattern
`test -z ... || rm -f ...` and replace with $(am__rm_f).

* NEWS: Mention support for `rm -f` w/out arguments.
* PLANS/rm-f-without-args.txt: Remove.
* lib/am/check.am: Use new $(am__rm_f) helper.
* lib/am/clean.am: Likewise.
* lib/am/header-vars.am: Likewise.
* lib/am/inst-vars.am: Likewise.
* lib/am/libs.am: Likewise.
* lib/am/ltlib.am: Likewise.
* lib/am/progs.am: Likewise.
* lib/am/texinfos.am: Likewise.
* m4/init.m4: Delete `rm -f` checks and call _AM_PROG_RM_F.
* m4/rmf.m4: Define new _AM_PROG_RM_F macro.
* t/rm-f-probe.sh: Update test.

13 files changed, 55 insertions, 118 deletions

diff --git a/NEWS b/NEWS
index c5ccd9387..512cdecd0 100644
--- a/NEWS
+++ b/NEWS
@@ -22,6 +22,10 @@ New in 1.17:
   - Generated file timestamp checks now handle filesystems with sub-second
     timestamp granularity dynamically.
 
+  - Systems with non-POSIX "rm -f" behavior are now supported, and intent to
+    drop support for them has been reversed.  The ACCEPT_INFERIOR_RM_PROGRAM
+    setting no longer exists.
+
 * Obsolescent features:
 
   - py-compile no longer supports Python 0.x or 1.x versions.  Python 2.0,
diff --git a/PLANS/rm-f-without-args.txt b/PLANS/rm-f-without-args.txt
deleted file mode 100644
index b940fc3e9..000000000
--- a/PLANS/rm-f-without-args.txt
+++ /dev/null
@@ -1,40 +0,0 @@
-Summary
--------
-
-POSIX will say in a future version that calling "rm -f" with no argument
-is OK; and this sensible behaviour seem to be already very widespread in
-"the wild" (and possibly lacking only on those systems that are well on
-their way to obsolescence).
-
-Se we'd like to simplify several automake-generated "cleaning" rules
-accordingly, to get rid of the awful idiom:
-
-  test -z "$(VAR)" || rm -f $(VAR)
-
-See automake bug#10828.
-
-For Automake 1.14 (DONE)
-------------------------
-
-Add a temporary "probe check" in AM_INIT_AUTOMAKE that verifies that
-the no-args "rm -f" usage is supported on the system configure is
-being run on; complain loudly if this is not the case, and tell the
-user to report the situation to us.
-
-For Automake 2.0
-----------------
-
-Make any failure in the configure-time probe check introduced by the
-previous point fatal; and in case of failure, also suggest to the user
-to install an older version of GNU coreutils to work around the
-limitation of his system (this version should be old enough not to
-be bootstrapped with Automake 2.0, otherwise the user will face a
-bootstrapping catch-22).
-
-In all our recipes, start assuming "rm -f" with no argument is OK;
-simplify and de-uglify the recipes accordingly.
-
-For Automake 3.0
-----------------
-
-Remove the runtime probe altogether.
diff --git a/lib/am/check.am b/lib/am/check.am
index a7201af76..6648c011d 100644
--- a/lib/am/check.am
+++ b/lib/am/check.am
@@ -405,8 +405,8 @@ RECHECK_LOGS = $(TEST_LOGS)
 ## ------------------------------------------ ##
 
 check-TESTS: %CHECK_DEPS%
-	@list='$(RECHECK_LOGS)';           test -z "$$list" || rm -f $$list
-	@list='$(RECHECK_LOGS:.log=.trs)'; test -z "$$list" || rm -f $$list
+	@list='$(RECHECK_LOGS)';           $(am__rm_f) $$list
+	@list='$(RECHECK_LOGS:.log=.trs)'; $(am__rm_f) $$list
 ## We always have to remove $(TEST_SUITE_LOG), to ensure its rule is run
 ## in any case even in lazy mode: otherwise, if no test needs rerunning,
 ## or a prior run plus reruns all happen within the same timestamp (can
@@ -414,7 +414,7 @@ check-TESTS: %CHECK_DEPS%
 ## OTOH, this means that, in the rule for '$(TEST_SUITE_LOG)', we
 ## cannot use '$?' to compute the set of lazily rerun tests, lest
 ## we rely on .PHONY to work portably.
-	@test -z "$(TEST_SUITE_LOG)" || rm -f $(TEST_SUITE_LOG)
+	@$(am__rm_f) $(TEST_SUITE_LOG)
 	@set +e; $(am__set_TESTS_bases); \
 	log_list=`for i in $$bases; do echo $$i.log; done`; \
 	trs_list=`for i in $$bases; do echo $$i.trs; done`; \
@@ -432,7 +432,7 @@ check-TESTS: %CHECK_DEPS%
 recheck: all %CHECK_DEPS%
 ## See comments above in the check-TESTS recipe for why remove
 ## $(TEST_SUITE_LOG) here.
-	@test -z "$(TEST_SUITE_LOG)" || rm -f $(TEST_SUITE_LOG)
+	@$(am__rm_f) $(TEST_SUITE_LOG)
 	@set +e; $(am__set_TESTS_bases); \
 ## We must only consider tests that had an unexpected outcome (FAIL
 ## or XPASS) in the earlier run.
diff --git a/lib/am/clean.am b/lib/am/clean.am
index 987e825ba..bf7eb8178 100644
--- a/lib/am/clean.am
+++ b/lib/am/clean.am
@@ -27,8 +27,8 @@ clean-generic:
 
 distclean-am: distclean-generic clean-am
 distclean-generic:
-	-test -z "$(CONFIG_CLEAN_FILES)" || rm -f $(CONFIG_CLEAN_FILES)
-	-test . = "$(srcdir)" || test -z "$(CONFIG_CLEAN_VPATH_FILES)" || rm -f $(CONFIG_CLEAN_VPATH_FILES)
+	-$(am__rm_f) $(CONFIG_CLEAN_FILES)
+	-test . = "$(srcdir)" || $(am__rm_f) $(CONFIG_CLEAN_VPATH_FILES)
 %DISTCLEAN_RMS%
 
 ## Makefiles and their dependencies cannot be cleaned by
diff --git a/lib/am/header-vars.am b/lib/am/header-vars.am
index cfc330e65..0256faed6 100644
--- a/lib/am/header-vars.am
+++ b/lib/am/header-vars.am
@@ -140,6 +140,10 @@ am__make_dryrun = (target_option=n; $(am__make_running_with_option))
 ## subdirectories, and decide whether to stop at the first error or not.
 am__make_keepgoing = (target_option=k; $(am__make_running_with_option))
 
+## Helper to handle `rm -f` failing with no arguments.
+am__rm_f = rm -f $(am__rm_f_notfound)
+am__rm_rf = rm -rf $(am__rm_f_notfound)
+
 ## Some derived variables that have been found to be useful.
 pkgdatadir = $(datadir)/@PACKAGE@
 pkgincludedir = $(includedir)/@PACKAGE@
diff --git a/lib/am/inst-vars.am b/lib/am/inst-vars.am
index c17dd625d..fd35a7de1 100644
--- a/lib/am/inst-vars.am
+++ b/lib/am/inst-vars.am
@@ -59,15 +59,13 @@ am__base_list = \
 ## to the directory where the files to be removed are, and to the list of
 ## such files.
 am__uninstall_files_from_dir = { \
-## Some rm implementations complain if 'rm -f' is used without arguments.
-  test -z "$$files" \
 ## At least Solaris /bin/sh still lacks 'test -e', so we use the multiple
 ## tests below instead.  We expect $dir to be either non-existent or a
 ## directory, so the failure we'll experience if it is a regular file
 ## is indeed desired and welcome (better to fail loudly thasn silently).
-    || { test ! -d "$$dir" && test ! -f "$$dir" && test ! -r "$$dir"; } \
-    || { echo " ( cd '$$dir' && rm -f" $$files ")"; \
-         $(am__cd) "$$dir" && rm -f $$files; }; \
+  { test ! -d "$$dir" && test ! -f "$$dir" && test ! -r "$$dir"; } \
+  || { echo " ( cd '$$dir' && rm -f" $$files ")"; \
+       $(am__cd) "$$dir" && $(am__rm_f) $$files; }; \
   }
 
 endif %?FIRST%
diff --git a/lib/am/libs.am b/lib/am/libs.am
index 52413521a..a5e175e93 100644
--- a/lib/am/libs.am
+++ b/lib/am/libs.am
@@ -103,4 +103,4 @@ endif %?INSTALL%
 
 .PHONY clean-am: clean-%DIR%LIBRARIES
 clean-%DIR%LIBRARIES:
-	-test -z "$(%DIR%_LIBRARIES)" || rm -f $(%DIR%_LIBRARIES)
+	-$(am__rm_f) $(%DIR%_LIBRARIES)
diff --git a/lib/am/ltlib.am b/lib/am/ltlib.am
index 6e3c065f4..032f88169 100644
--- a/lib/am/ltlib.am
+++ b/lib/am/ltlib.am
@@ -109,7 +109,7 @@ endif %?INSTALL%
 
 .PHONY clean-am: clean-%DIR%LTLIBRARIES
 clean-%DIR%LTLIBRARIES:
-	-test -z "$(%DIR%_LTLIBRARIES)" || rm -f $(%DIR%_LTLIBRARIES)
+	-$(am__rm_f) $(%DIR%_LTLIBRARIES)
 ## 'so_locations' files are created by some linkers (IRIX, OSF) when
 ## building a shared object.  Libtool places these files in the
 ## directory where the shared object is created.
@@ -117,7 +117,5 @@ clean-%DIR%LTLIBRARIES:
 	locs=`for p in $$list; do echo $$p; done | \
 	      sed 's|^[^/]*$$|.|; s|/[^/]*$$||; s|$$|/so_locations|' | \
 	      sort -u`; \
-	test -z "$$locs" || { \
-	  echo rm -f $${locs}; \
-	  rm -f $${locs}; \
-	}
+	echo rm -f $${locs}; \
+	$(am__rm_f) $${locs}
diff --git a/lib/am/progs.am b/lib/am/progs.am
index 8b99ec5a8..753886a31 100644
--- a/lib/am/progs.am
+++ b/lib/am/progs.am
@@ -95,7 +95,7 @@ uninstall-%DIR%PROGRAMS:
 	`; \
 	test -n "$$list" || exit 0; \
 	echo " ( cd '$(DESTDIR)$(%NDIR%dir)' && rm -f" $$files ")"; \
-	cd "$(DESTDIR)$(%NDIR%dir)" && rm -f $$files
+	cd "$(DESTDIR)$(%NDIR%dir)" && $(am__rm_f) $$files
 endif %?INSTALL%
 
 
@@ -105,7 +105,7 @@ endif %?INSTALL%
 
 .PHONY clean-am: clean-%DIR%PROGRAMS
 clean-%DIR%PROGRAMS:
-?!LIBTOOL?	-test -z "$(%DIR%_PROGRAMS)" || rm -f $(%DIR%_PROGRAMS)
+?!LIBTOOL?	-$(am__rm_f) $(%DIR%_PROGRAMS)
 ## Under Cygwin, we build 'program$(EXEEXT)'.  However, if this
 ## program uses a Libtool library, Libtool will move it in
 ## '_libs/program$(EXEEXT)' and create a 'program' wrapper (without
diff --git a/lib/am/texinfos.am b/lib/am/texinfos.am
index 4284b1ea7..896a2a007 100644
--- a/lib/am/texinfos.am
+++ b/lib/am/texinfos.am
@@ -386,14 +386,13 @@ mostlyclean-aminfo:
 ## Use '-rf', not just '-f', because the %*CLEAN% substitutions can also
 ## contain any directory created by "makeinfo --html", as well as the
 ## '*.t2d' and '*.t2p' directories used by texi2dvi and texi2pdf.
-	-rm -rf %MOSTLYCLEAN%
+	-$(am__rm_rf) %MOSTLYCLEAN%
 
 .PHONY clean-am: clean-aminfo
 clean-aminfo:
 ## Use '-rf', not just '-f'; see comments in 'mostlyclean-aminfo'
 ## above for details.
-?TEXICLEAN?	-test -z "%TEXICLEAN%" \
-?TEXICLEAN?	|| rm -rf %TEXICLEAN%
+?TEXICLEAN?	-$(am__rm_rf) %TEXICLEAN%
 
 .PHONY maintainer-clean-am: maintainer-clean-aminfo
 maintainer-clean-aminfo:
@@ -405,7 +404,6 @@ maintainer-clean-aminfo:
 	done
 ## Use '-rf', not just '-f'; see comments in 'mostlyclean-aminfo'
 ## above for details.
-?MAINTCLEAN?	-test -z "%MAINTCLEAN%" \
-?MAINTCLEAN?	|| rm -rf %MAINTCLEAN%
+?MAINTCLEAN?	-$(am__rm_rf) %MAINTCLEAN%
 
 endif %?LOCAL-TEXIS%
diff --git a/m4/init.m4 b/m4/init.m4
index 6ef46d669..e576b935d 100644
--- a/m4/init.m4
+++ b/m4/init.m4
@@ -142,47 +142,8 @@ AC_CONFIG_COMMANDS_PRE(dnl
 [m4_provide_if([_AM_COMPILER_EXEEXT],
   [AM_CONDITIONAL([am__EXEEXT], [test -n "$EXEEXT"])])])dnl
 
-# POSIX will say in a future version that running "rm -f" with no argument
-# is OK; and we want to be able to make that assumption in our Makefile
-# recipes.  So use an aggressive probe to check that the usage we want is
-# actually supported "in the wild" to an acceptable degree.
-# See automake bug#10828.
-# To make any issue more visible, cause the running configure to be aborted
-# by default if the 'rm' program in use doesn't match our expectations; the
-# user can still override this though.
-if rm -f && rm -fr && rm -rf; then : OK; else
-  cat >&2 <<'END'
-Oops!
+AC_REQUIRE([_AM_PROG_RM_F])
 
-Your 'rm' program seems unable to run without file operands specified
-on the command line, even when the '-f' option is present.  This is contrary
-to the behaviour of most rm programs out there, and not conforming with
-the upcoming POSIX standard: <http://austingroupbugs.net/view.php?id=542>
-
-Please tell bug-automake@gnu.org about your system, including the value
-of your $PATH and any error possibly output before this message.  This
-can help us improve future automake versions.
-
-END
-  if test x"$ACCEPT_INFERIOR_RM_PROGRAM" = x"yes"; then
-    echo 'Configuration will proceed anyway, since you have set the' >&2
-    echo 'ACCEPT_INFERIOR_RM_PROGRAM variable to "yes"' >&2
-    echo >&2
-  else
-    cat >&2 <<'END'
-Aborting the configuration process, to ensure you take notice of the issue.
-
-You can download and install GNU coreutils to get an 'rm' implementation
-that behaves properly: <https://www.gnu.org/software/coreutils/>.
-
-If you want to complete the configuration process using your problematic
-'rm' anyway, export the environment variable ACCEPT_INFERIOR_RM_PROGRAM
-to "yes", and re-run configure.
-
-END
-    AC_MSG_ERROR([Your 'rm' program is bad, sorry.])
-  fi
-fi
 dnl The trailing newline in this macro's definition is deliberate, for
 dnl backward compatibility and to allow trailing 'dnl'-style comments
 dnl after the AM_INIT_AUTOMAKE invocation. See automake bug#16841.
diff --git a/m4/rmf.m4 b/m4/rmf.m4
new file mode 100644
index 000000000..2437a9f76
--- /dev/null
+++ b/m4/rmf.m4
@@ -0,0 +1,16 @@
+##                                                          -*- Autoconf -*-
+# Copyright (C) 2022 Free Software Foundation, Inc.
+#
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+# _AM_PROG_RM_F
+# ---------------
+# Check whether 'rm -f' without any arguments works.
+# https://bugs.gnu.org/10828
+AC_DEFUN([_AM_PROG_RM_F],
+[am__rm_f_notfound=
+AS_IF([(rm -f && rm -fr && rm -rf) 2>/dev/null], [], [am__rm_f_notfound='""'])
+AC_SUBST(am__rm_f_notfound)
+])
diff --git a/t/rm-f-probe.sh b/t/rm-f-probe.sh
index 9cd3e8814..8463f4fb6 100644
--- a/t/rm-f-probe.sh
+++ b/t/rm-f-probe.sh
@@ -14,8 +14,8 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-# Verify our probe that checks that "rm -f" doesn't complain if called
-# without file operands works as expected.  See automake bug#10828.
+# Verify our probe that checks that "rm -f" behavior works.
+# https://bugs.gnu.org/10828
 
 . test-init.sh
 
@@ -40,8 +40,8 @@ while test $# -gt 0; do
   shift
 done
 if test $# -eq 0; then
-  echo "Oops, fake rm called without arguments" >&2
-  exit 1
+  echo "Oops, fake rm called without arguments" >&2 #DELETE
+  exit 1 #CHANGE
 else
   exec rm $rm_opts "$@"
 fi
@@ -54,19 +54,17 @@ export PATH original_PATH
 
 rm -f && exit 99 # Sanity check.
 
-./configure 2>stderr && { cat stderr >&2; exit 1; }
-cat stderr >&2
-
-grep "'rm' program.* unable to run without file operands" stderr
-$FGREP "tell bug-automake@gnu.org about your system" stderr
-$FGREP "install GNU coreutils" stderr
-$EGREP "(^| |')ACCEPT_INFERIOR_RM_PROGRAM($| |')" stderr
+# Check that `rm -f` is detected as broken.
+./configure
+grep '^am__rm_f_notfound = ""$' Makefile
 
-ACCEPT_INFERIOR_RM_PROGRAM=yes; export ACCEPT_INFERIOR_RM_PROGRAM
+# Chagne the `rm -f` behavior to work.
+sed -e '/#DELETE/d' -e '/#CHANGE/s:1:0:' bin/rm > bin/rm.tmp
+cat bin/rm.tmp > bin/rm
 
+# Check that `rm -f` is detected as working.
 ./configure
-$MAKE
-$MAKE distcheck
+grep '^am__rm_f_notfound = *$' Makefile
 
 # For the sake of our exit trap.
 PATH=$original_PATH; export PATH