Overhaul Erlang support.

Erlang is similar to Java in that it doesn’t compile to standalone
machine code; the output of ‘erlc’ is byte-code files that are then
interpreted by ‘erl’.  We handle this poorly in a whole bunch of ways,
particularly when cross-compiling.  This patch fixes up the more
serious problems:

 - AC_COMPILE_IFELSE now actually works when AC_LANG([Erlang]) is in
   effect.
 - ‘conftest.beam’ is now deleted in several more places where it
   could be created.
 - The various AC_ERLANG_* macros that interrogate the runtime
   environment do so by invoking ‘$ERL’ directly, rather than using
   AC_RUN_IFELSE, and thus do not crash the configure script when
   we think we’re cross-compiling.  (It is not clear to me whether
   they get the correct answer when cross-compiling, but this should
   still be strictly an improvement.)
 - The Erlang-related tests have been streamlined.

Further improvements are definitely possible, but we’d have to teach
the infrastructure to make $ac_objext language-specific first, which
seems like too big of a change for 2.70.

(This patch is all fallout from a logically unrelated testsuite change
which is coming up next.  Gotta love the fundamental interconnectedness
of things.)

* lib/autoconf/general.m4 (_AC_COMPILE_IFELSE_BODY)
  (_AC_LINK_IFELSE_BODY): Delete conftest.beam as well as conftest.$ac_objext.

* lib/autoconf/erlang.m4 (AC_ERLANG_PATH_ERLC, AC_ERLANG_PATH_ERL):
  Don’t repeat work done by AC_PATH_TOOL.
  (Erlang $ac_compile): Fake an .o file so AC_TRY_COMPILE will be happy.
  (AC_LANG_COMPILER(Erlang)): AC_REQUIRE AC_ERLANG_NEED_ERLC, not
  AC_ERLANG_PATH_ERLC.  Also AC_REQUIRE AC_ERLANG_NEED_ERL so
  AC_RUN_IFELSE works reliably.
  (AC_ERLANG_CHECK_LIB, AC_ERLANG_SUBST_ROOT_DIR)
  (AC_ERLANG_SUBST_LIB_DIR, AC_ERLANG_SUBST_ERTS_VER):
  Use $ERL -eval, not AC_RUN_IFELSE.
  No need to AC_REQUIRE AC_ERLANG_NEED_ERLC.

* tests/erlang.at: Don’t test anything here that’s tested adequately
  by acerlang.at; document which macros those are expected to be.
  Remove unnecessary AC_ERLANG_PATH_ERL/ERLC invocations throughout.
  (AT_CHECK_MACRO([Erlang])): Rename test to ‘Erlang basic compilation’;
  expect both AC_COMPILE_IFELSE and AC_RUN_IFELSE to work;
  handle cross compilation mode properly.
* tests/mktests.sh: Exclude from acerlang.at all macros completely
  covered by erlang.at.

4 files changed, 84 insertions, 148 deletions

diff --git a/lib/autoconf/erlang.m4 b/lib/autoconf/erlang.m4
index ad423b16..b1d3ab1f 100644
--- a/lib/autoconf/erlang.m4
+++ b/lib/autoconf/erlang.m4
@@ -48,13 +48,8 @@
 # -------------------------------------------------
 AC_DEFUN([AC_ERLANG_PATH_ERLC],
 [AC_ARG_VAR([ERLC], [Erlang/OTP compiler command [autodetected]])dnl
-if test -n "$ERLC"; then
-    AC_MSG_CHECKING([for erlc])
-    AC_MSG_RESULT([$ERLC])
-else
-    AC_PATH_TOOL(ERLC, erlc, [$1], [$2])
-fi
 AC_ARG_VAR([ERLCFLAGS], [Erlang/OTP compiler flags [none]])dnl
+AC_PATH_TOOL(ERLC, erlc, [$1], [$2])
 ])
 
 
@@ -72,12 +67,7 @@ fi
 # ------------------------------------------------
 AC_DEFUN([AC_ERLANG_PATH_ERL],
 [AC_ARG_VAR([ERL], [Erlang/OTP interpreter command [autodetected]])dnl
-if test -n "$ERL"; then
-    AC_MSG_CHECKING([for erl])
-    AC_MSG_RESULT([$ERL])
-else
-    AC_PATH_TOOL(ERL, erl, [$1], [$2])[]dnl
-fi
+AC_PATH_TOOL(ERL, erl, [$1], [$2])
 ])
 
 
@@ -101,7 +91,8 @@ fi
 # ---------------
 AC_LANG_DEFINE([Erlang], [erl], [ERL], [ERLC], [],
 [ac_ext=erl
-ac_compile='$ERLC $ERLCFLAGS -b beam conftest.$ac_ext >&AS_MESSAGE_LOG_FD'
+: ${ac_objext=o}
+ac_compile='$ERLC $ERLCFLAGS -b beam conftest.$ac_ext >&AS_MESSAGE_LOG_FD && ln -sf conftest.beam conftest.$ac_objext'
 ac_link='$ERLC $ERLCFLAGS -b beam conftest.$ac_ext >&AS_MESSAGE_LOG_FD && echo "[#]!/bin/sh" > conftest$ac_exeext && AS_ECHO(["\"$ERL\" -run conftest start -run init stop -noshell"]) >> conftest$ac_exeext && chmod +x conftest$ac_exeext'
 ])
 
@@ -164,8 +155,11 @@ AC_DEFUN([AC_LANG_PREPROC(Erlang)],
 # AC_LANG_COMPILER(Erlang)
 # ------------------------
 # Find the Erlang compiler.  Must be AC_DEFUN'd to be AC_REQUIRE'able.
+# Technically we only need erlc to compile, but there's no AC_LANG_DISPATCH
+# hook specifically for AC_RUN_IFELSE, so we need to find erl here too.
 AC_DEFUN([AC_LANG_COMPILER(Erlang)],
-[AC_REQUIRE([AC_ERLANG_PATH_ERLC])])
+[AC_REQUIRE([AC_ERLANG_NEED_ERLC])
+AC_REQUIRE([AC_ERLANG_NEED_ERL])])
 
 
 # AC_ERLANG_CHECK_LIB(LIBRARY, [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
@@ -173,37 +167,22 @@ AC_DEFUN([AC_LANG_COMPILER(Erlang)],
 # Macro for checking if an Erlang library is installed, and to
 # determine its version.
 AC_DEFUN([AC_ERLANG_CHECK_LIB],
-[AC_REQUIRE([AC_ERLANG_NEED_ERLC])[]dnl
-AC_REQUIRE([AC_ERLANG_NEED_ERL])[]dnl
+[AC_REQUIRE([AC_ERLANG_NEED_ERL])[]dnl
 AC_CACHE_CHECK([for Erlang/OTP '$1' library subdirectory],
     [ac_cv_erlang_lib_dir_$1],
-    [AC_LANG_PUSH(Erlang)[]dnl
-     AC_RUN_IFELSE(
-	[AC_LANG_PROGRAM([], [dnl
-	    ReturnValue = case code:lib_dir("[$1]") of
-	    {error, bad_name} ->
-		file:write_file("conftest.out", "not found\n"),
-		1;
-	    LibDir ->
-		file:write_file("conftest.out", LibDir),
-		0
-	    end,
-	    halt(ReturnValue)])],
-	[ac_cv_erlang_lib_dir_$1=`cat conftest.out`
-	 rm -f conftest.out],
-	[if test ! -f conftest.out; then
-	     AC_MSG_FAILURE([test Erlang program execution failed])
-	 else
-	     ac_cv_erlang_lib_dir_$1="not found"
-	     rm -f conftest.out
-	 fi])
-     AC_LANG_POP(Erlang)[]dnl
-    ])
+    [ac_cv_erlang_lib_dir_$1=`$ERL -noshell -eval '
+        case code:lib_dir("$1") of
+            {error, bad_name} -> io:format("not found~n");
+            LibDir -> io:format("~s~n", @<:@LibDir@:>@)
+        end,
+        halt(0)
+    '`])
 AC_CACHE_CHECK([for Erlang/OTP '$1' library version],
     [ac_cv_erlang_lib_ver_$1],
     [AS_IF([test "$ac_cv_erlang_lib_dir_$1" = "not found"],
-	[ac_cv_erlang_lib_ver_$1="not found"],
-	[ac_cv_erlang_lib_ver_$1=`AS_ECHO(["$ac_cv_erlang_lib_dir_$1"]) | sed -n -e 's,^.*-\([[^/-]]*\)$,\1,p'`])[]dnl
+        [ac_cv_erlang_lib_ver_$1="not found"],
+        [ac_cv_erlang_lib_ver_$1=`AS_ECHO(["$ac_cv_erlang_lib_dir_$1"]) |
+            sed -n -e 's,^.*-\([[^/-]]*\)$,\1,p'`])[]dnl
     ])
 AC_SUBST([ERLANG_LIB_DIR_$1], [$ac_cv_erlang_lib_dir_$1])
 AC_SUBST([ERLANG_LIB_VER_$1], [$ac_cv_erlang_lib_ver_$1])
@@ -215,23 +194,13 @@ AS_IF([test "$ac_cv_erlang_lib_dir_$1" = "not found"], [$3], [$2])
 # ------------------------
 # Determines the Erlang/OTP root directory.
 AC_DEFUN([AC_ERLANG_SUBST_ROOT_DIR],
-[AC_REQUIRE([AC_ERLANG_NEED_ERLC])[]dnl
-AC_REQUIRE([AC_ERLANG_NEED_ERL])[]dnl
+[AC_REQUIRE([AC_ERLANG_NEED_ERL])[]dnl
 AC_CACHE_CHECK([for Erlang/OTP root directory],
     [ac_cv_erlang_root_dir],
-    [AC_LANG_PUSH(Erlang)[]dnl
-     AC_RUN_IFELSE(
-	[AC_LANG_PROGRAM([], [dnl
-	    RootDir = code:root_dir(),
-	    file:write_file("conftest.out", RootDir),
-	    ReturnValue = 0,
-	    halt(ReturnValue)])],
-	[ac_cv_erlang_root_dir=`cat conftest.out`
-	 rm -f conftest.out],
-	[rm -f conftest.out
-	 AC_MSG_FAILURE([test Erlang program execution failed])])
-     AC_LANG_POP(Erlang)[]dnl
-    ])
+    [ac_cv_erlang_root_dir=`$ERL -noshell -eval '
+        io:format("~s~n", @<:@code:root_dir()@:>@),
+        halt(0)
+    '`])
 AC_SUBST([ERLANG_ROOT_DIR], [$ac_cv_erlang_root_dir])
 ])# AC_ERLANG_SUBST_ROOT_DIR
 
@@ -239,23 +208,13 @@ AC_SUBST([ERLANG_ROOT_DIR], [$ac_cv_erlang_root_dir])
 # AC_ERLANG_SUBST_LIB_DIR
 # -----------------------
 AC_DEFUN([AC_ERLANG_SUBST_LIB_DIR],
-[AC_REQUIRE([AC_ERLANG_NEED_ERLC])[]dnl
-AC_REQUIRE([AC_ERLANG_NEED_ERL])[]dnl
+[AC_REQUIRE([AC_ERLANG_NEED_ERL])[]dnl
 AC_CACHE_CHECK([for Erlang/OTP library base directory],
     [ac_cv_erlang_lib_dir],
-    [AC_LANG_PUSH(Erlang)[]dnl
-     AC_RUN_IFELSE(
-	[AC_LANG_PROGRAM([], [dnl
-	    LibDir = code:lib_dir(),
-	    file:write_file("conftest.out", LibDir),
-	    ReturnValue = 0,
-	    halt(ReturnValue)])],
-	[ac_cv_erlang_lib_dir=`cat conftest.out`
-	 rm -f conftest.out],
-	[rm -f conftest.out
-	 AC_MSG_FAILURE([test Erlang program execution failed])])
-     AC_LANG_POP(Erlang)[]dnl
-    ])
+    [ac_cv_erlang_lib_dir=`$ERL -noshell -eval '
+        io:format("~s~n", @<:@code:lib_dir()@:>@),
+        halt(0)
+    '`])
 AC_SUBST([ERLANG_LIB_DIR], [$ac_cv_erlang_lib_dir])
 ])# AC_ERLANG_SUBST_LIB_DIR
 
@@ -299,22 +258,12 @@ fi
 # ------------------------
 # Determines the Erlang runtime system version.
 AC_DEFUN([AC_ERLANG_SUBST_ERTS_VER],
-[AC_REQUIRE([AC_ERLANG_NEED_ERLC])[]dnl
-AC_REQUIRE([AC_ERLANG_NEED_ERL])[]dnl
+[AC_REQUIRE([AC_ERLANG_NEED_ERL])[]dnl
 AC_CACHE_CHECK([for Erlang/OTP ERTS version],
     [ac_cv_erlang_erts_ver],
-    [AC_LANG_PUSH([Erlang])[]dnl
-     AC_RUN_IFELSE(
-	[AC_LANG_PROGRAM([], [dnl
-	    Version = erlang:system_info(version),
-	    file:write_file("conftest.out", Version),
-	    ReturnValue = 0,
-	    halt(ReturnValue)])],
-	[ac_cv_erlang_erts_ver=`cat conftest.out`
-	 rm -f conftest.out],
-	[rm -f conftest.out
-	 AC_MSG_FAILURE([test Erlang program execution failed])])
-     AC_LANG_POP([Erlang])[]dnl
-    ])
+    [ac_cv_erlang_erts_ver=`$ERL -noshell -eval '
+        io:format("~s~n", @<:@erlang:system_info(version)@:>@),
+        halt(0)
+    '`])
 AC_SUBST([ERLANG_ERTS_VER], [$ac_cv_erlang_erts_ver])
 ])# AC_ERLANG_SUBST_ERTS_VER
diff --git a/lib/autoconf/general.m4 b/lib/autoconf/general.m4
index f75b2dbb..16f0d074 100644
--- a/lib/autoconf/general.m4
+++ b/lib/autoconf/general.m4
@@ -2802,7 +2802,7 @@ AC_DEFUN([AC_EGREP_HEADER],
 # Shell function body for _AC_COMPILE_IFELSE.
 m4_define([_AC_COMPILE_IFELSE_BODY],
 [  AS_LINENO_PUSH([$[]1])
-  rm -f conftest.$ac_objext
+  rm -f conftest.$ac_objext conftest.beam
   AS_IF([_AC_DO_STDERR($ac_compile) && {
 	 test -z "$ac_[]_AC_LANG_ABBREV[]_werror_flag" ||
 	 test ! -s conftest.err
@@ -2826,7 +2826,7 @@ AC_DEFUN([_AC_COMPILE_IFELSE],
   [$0_BODY])]dnl
 [m4_ifvaln([$1], [AC_LANG_CONFTEST([$1])])]dnl
 [AS_IF([ac_fn_[]_AC_LANG_ABBREV[]_try_compile "$LINENO"], [$2], [$3])
-rm -f core conftest.err conftest.$ac_objext[]m4_ifval([$1], [ conftest.$ac_ext])[]dnl
+rm -f core conftest.err conftest.$ac_objext conftest.beam[]m4_ifval([$1], [ conftest.$ac_ext])[]dnl
 ])# _AC_COMPILE_IFELSE
 
 
@@ -2858,7 +2858,7 @@ AU_DEFUN([AC_TRY_COMPILE],
 # Shell function body for _AC_LINK_IFELSE.
 m4_define([_AC_LINK_IFELSE_BODY],
 [  AS_LINENO_PUSH([$[]1])
-  rm -f conftest.$ac_objext conftest$ac_exeext
+  rm -f conftest.$ac_objext conftest.beam conftest$ac_exeext
   AS_IF([_AC_DO_STDERR($ac_link) && {
 	 test -z "$ac_[]_AC_LANG_ABBREV[]_werror_flag" ||
 	 test ! -s conftest.err
@@ -2897,7 +2897,7 @@ AC_DEFUN([_AC_LINK_IFELSE],
   [$0_BODY])]dnl
 [m4_ifvaln([$1], [AC_LANG_CONFTEST([$1])])]dnl
 [AS_IF([ac_fn_[]_AC_LANG_ABBREV[]_try_link "$LINENO"], [$2], [$3])
-rm -f core conftest.err conftest.$ac_objext \
+rm -f core conftest.err conftest.$ac_objext conftest.beam \
     conftest$ac_exeext[]m4_ifval([$1], [ conftest.$ac_ext])[]dnl
 ])# _AC_LINK_IFELSE
 
diff --git a/tests/erlang.at b/tests/erlang.at
index c149f776..93a0e478 100644
--- a/tests/erlang.at
+++ b/tests/erlang.at
@@ -1,5 +1,11 @@
 #							-*- Autotest -*-
 
+# Macros tested in acerlang.at:
+# AC_ERLANG_PATH_ERL
+# AC_ERLANG_PATH_ERLC
+# AC_ERLANG_SUBST_ERTS_VER
+# AU::AC_LANG_ERLANG
+
 AT_BANNER([Erlang low level compiling and utility macros.])
 
 # Copyright (C) 2009-2017, 2020 Free Software Foundation, Inc.
@@ -27,22 +33,30 @@ AT_BANNER([Erlang low level compiling and utility macros.])
 ## Erlang Compiler.  ##
 ## ----------------- ##
 
-AT_CHECK_MACRO([Erlang],
-[[AC_ERLANG_PATH_ERL([no])
-AC_ERLANG_PATH_ERLC([no])
-if test "$ERL" = "no" || test "$ERLC" = "no"; then AS_EXIT([77]); fi
-AC_LANG([Erlang])
-## Can't compile, but can run an Erlang module:
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [halt(0)])],
-		  [AC_MSG_RESULT([ok])
-		   AC_MSG_ERROR([compiling Erlang program should fail])],
-		  [AC_MSG_RESULT([failed])])
-AC_RUN_IFELSE([AC_LANG_PROGRAM([], [halt(0)])],
-	      [AC_MSG_RESULT([ok])],
-	      [AC_MSG_RESULT([failed])
-	       AC_MSG_ERROR([could not run test program])])
-]],
-[AT_KEYWORDS([Erlang])])
+AT_CHECK_MACRO([Erlang basic compilation],
+[[AC_LANG([Erlang])
+
+AC_CACHE_CHECK([whether erlc works], [ac_cv_erlang_erlc_works],
+ [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [halt(0)])],
+   [ac_cv_erlang_erlc_works=yes],
+   [ac_cv_erlang_erlc_works=no])])
+
+if test $ac_cv_erlang_erlc_works = no; then
+  AC_MSG_ERROR([could not compile a test Erlang module])
+fi
+
+# To keep AT_CHECK_MACRO happy, we lie and say that erl does work
+# when cross compiling.
+AC_CACHE_CHECK([whether erl works], [ac_cv_erlang_erl_works],
+  [AC_RUN_IFELSE([AC_LANG_PROGRAM([], [halt(0)])],
+    [ac_cv_erlang_erl_works=yes],
+    [ac_cv_erlang_erl_works=no],
+    [ac_cv_erlang_erl_works=yes])])
+
+if test $ac_cv_erlang_erl_works = no; then
+  AC_MSG_ERROR([could not run a test Erlang module])
+fi
+]])
 
 
 ## ---------------------- ##
@@ -50,19 +64,15 @@ AC_RUN_IFELSE([AC_LANG_PROGRAM([], [halt(0)])],
 ## ---------------------- ##
 
 AT_CHECK_MACRO([AC_ERLANG_CHECK_LIB],
-[[AC_ERLANG_PATH_ERL([no])
-AC_ERLANG_PATH_ERLC([no])
-if test "$ERL" = "no" || test "$ERLC" = "no"; then AS_EXIT([77]); fi
-AC_ERLANG_CHECK_LIB([stdlib],
-		    [AC_MSG_RESULT([ok])],
-		    [AC_MSG_RESULT([failed])])
+[[AC_ERLANG_CHECK_LIB([stdlib])
+if test "$ERLANG_LIB_DIR_stdlib" = "not found"; then
+  AC_MSG_ERROR([failed to find the Erlang stdlib])
+fi
 ## Test that the lib path detection really detected a directory:
-if test "$ERLANG_LIB_DIR_stdlib" != "not found" \
-  && test ! -d "$ERLANG_LIB_DIR_stdlib"; then
-	AC_MSG_ERROR([incorrect ERLANG_LIB_DIR_stdlib variable])
+if test ! -d "$ERLANG_LIB_DIR_stdlib"; then
+  AC_MSG_ERROR([incorrect ERLANG_LIB_DIR_stdlib variable])
 fi
-]],
-[AT_KEYWORDS([Erlang])])
+]])
 
 
 ## --------------------------- ##
@@ -70,16 +80,12 @@ fi
 ## --------------------------- ##
 
 AT_CHECK_MACRO([AC_ERLANG_SUBST_ROOT_DIR],
-[[AC_ERLANG_PATH_ERL([no])
-AC_ERLANG_PATH_ERLC([no])
-if test "$ERL" = "no" || test "$ERLC" = "no"; then AS_EXIT([77]); fi
-AC_ERLANG_SUBST_ROOT_DIR
+[[AC_ERLANG_SUBST_ROOT_DIR
 ## Test that the root path detection really detected a directory:
 if test ! -d "$ERLANG_ROOT_DIR"; then
 	AC_MSG_ERROR([incorrect ERLANG_ROOT_DIR variable])
 fi
-]],
-[AT_KEYWORDS([Erlang])])
+]])
 
 
 ## -------------------------- ##
@@ -87,10 +93,7 @@ fi
 ## -------------------------- ##
 
 AT_CHECK_MACRO([AC_ERLANG_SUBST_LIB_DIR],
-[[AC_ERLANG_PATH_ERL([no])
-AC_ERLANG_PATH_ERLC([no])
-if test "$ERL" = "no" || test "$ERLC" = "no"; then AS_EXIT([77]); fi
-AC_ERLANG_SUBST_LIB_DIR
+[[AC_ERLANG_SUBST_LIB_DIR
 ## Test that the lib path detection really detected a directory:
 if test ! -d "$ERLANG_LIB_DIR"; then
 	AC_MSG_ERROR([incorrect ERLANG_LIB_DIR variable])
@@ -99,14 +102,6 @@ fi
 [AT_KEYWORDS([Erlang])])
 
 
-## ----------------------------------- ##
-## Erlang install base dir detection.  ##
-## ----------------------------------- ##
-
-AT_CHECK_MACRO([AC_ERLANG_SUBST_INSTALL_LIB_DIR],
-	       [AT_KEYWORDS([Erlang])])
-
-
 ## ---------------------------------- ##
 ## Erlang install lib dir detection.  ##
 ## ---------------------------------- ##
@@ -114,21 +109,9 @@ AT_CHECK_MACRO([AC_ERLANG_SUBST_INSTALL_LIB_DIR],
 AT_CHECK_MACRO([AC_ERLANG_SUBST_INSTALL_LIB_SUBDIR],
 [[AC_ERLANG_SUBST_INSTALL_LIB_SUBDIR([test_blah], [1.24-b])
 ## Test that the generated directory name is well-formed:
-if test `echo "$ERLANG_INSTALL_LIB_DIR_test_blah" | sed -e 's/^.*\///'` != "test_blah-1.24-b"; then
+if test `echo "$ERLANG_INSTALL_LIB_DIR_test_blah" | sed -e 's/^.*\///'` \
+   != "test_blah-1.24-b"; then
 	AC_MSG_ERROR([incorrect ERLANG_INSTALL_LIB_DIR_test_blah variable])
 fi
 ]],
 [AT_KEYWORDS([Erlang])])
-
-
-## -------------------------- ##
-## Erlang version detection.  ##
-## -------------------------- ##
-
-AT_CHECK_MACRO([AC_ERLANG_SUBST_ERTS_VER],
-[[AC_ERLANG_PATH_ERL([no])
-AC_ERLANG_PATH_ERLC([no])
-if test "$ERL" = "no" || test "$ERLC" = "no"; then AS_EXIT([77]); fi
-AC_ERLANG_SUBST_ERTS_VER
-]],
-[AT_KEYWORDS([Erlang])])
diff --git a/tests/mktests.sh b/tests/mktests.sh
index 3ce0c2b4..34458a27 100755
--- a/tests/mktests.sh
+++ b/tests/mktests.sh
@@ -146,6 +146,10 @@ ac_exclude_list='
 
 	# Tested alongside m4_divert_text.
 	/^AC_PRESERVE_HELP_ORDER$/ {next}
+
+	# Tested in erlang.at.
+	/^AC_ERLANG_SUBST_(INSTALL_LIB_SUBDIR|ROOT_DIR)$/ {next}
+	/^AC_ERLANG_CHECK_LIB$/ {next}
 '