https://git.ruby-lang.org/ruby.git/commit/?id=50b18e8129

From 50b18e81295ad2d45975e4d8ea1e0c7e85140b97 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=8D=9C=E9=83=A8=E6=98=8C=E5=B9=B3?=
 <shyouhei@r...>
Date: Thu, 3 Sep 2020 15:06:56 +0900
Subject: configure: detect that there is no g++

AC_PROG_CXX checks for several C++ compilers INCLUDING g++.  When none
of them were found it sets the CXX variable to be g++.  This doesn't
make any sense.  Absense of g++ has already been made sure.

Because we don't want insanity (that's the whole reason we test the
environment using autoconf), we need to swipe such insane variable out.

diff --git a/configure.ac b/configure.ac
index e4a7542..cbfce07 100644
--- a/configure.ac
+++ b/configure.ac
@@ -197,6 +197,14 @@ AC_CHECK_TOOLS([STRIP],   [gstrip strip], [:]) https://github.com/ruby/ruby/blob/trunk/configure.ac#L197
 AS_IF([test ! $rb_test_CFLAGS], [AS_UNSET(CFLAGS)]); AS_UNSET(rb_test_CFLAGS)
 AS_IF([test ! $rb_test_CXXFLAGS], [AS_UNSET(CXXFLAGS)]); AS_UNSET(rb_save_CXXFLAGS)
 
+AS_IF([test "${CXX}" = "g++" -a -z "${GXX}"], [
+    # AC_PROG_CXX sets $CXX to "g++" when it purposefully finds that there is
+    # _no_ g++.  This brain-damaged design must be worked around.  Thankfully,
+    # similar thing doesn't happen for AC_PROG_CC.
+    AC_MSG_NOTICE([C++ features disabled due to lack of a C++ compiler.])
+    AS_UNSET(CXX)
+])
+
 test x"$target_alias" = x &&
 target_os=`echo $target_os | sed 's/linux-gnu$/linux/;s/linux-gnu/linux-/'`
 ac_install_sh='' # unusable for extension libraries.
-- 
cgit v0.10.2


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