diff --git a/m4/ax_boost_base.m4 b/m4/ax_boost_base.m4
index 2bce5194..519f1c9d 100644
--- a/m4/ax_boost_base.m4
+++ b/m4/ax_boost_base.m4
@@ -33,7 +33,7 @@
 #   and this notice are preserved. This file is offered as-is, without any
 #   warranty.
 
-#serial 43
+#serial 49
 
 # example boost program (need to pass version)
 m4_define([_AX_BOOST_BASE_PROGRAM],
@@ -113,7 +113,8 @@ AC_DEFUN([_AX_BOOST_BASE_RUNDETECT],[
     dnl are found, e.g. when only header-only libraries are installed!
     AS_CASE([${host_cpu}],
       [x86_64],[libsubdirs="lib64 libx32 lib lib64"],
-      [ppc64|s390x|sparc64|aarch64|ppc64le],[libsubdirs="lib64 lib lib64"],
+      [mips*64*],[libsubdirs="lib64 lib32 lib lib64"],
+      [ppc64|powerpc64|s390x|sparc64|aarch64|ppc64le|powerpc64le|riscv64|e2k],[libsubdirs="lib64 lib lib64"],
       [libsubdirs="lib"]
     )
 
@@ -122,6 +123,7 @@ AC_DEFUN([_AX_BOOST_BASE_RUNDETECT],[
     dnl are almost assuredly the ones desired.
     AS_CASE([${host_cpu}],
       [i?86],[multiarch_libsubdir="lib/i386-${host_os}"],
+      [armv7l],[multiarch_libsubdir="lib/arm-${host_os}"],
       [multiarch_libsubdir="lib/${host_cpu}-${host_os}"]
     )
 
diff --git a/m4/ax_cxx_compile_stdcxx.m4 b/m4/ax_cxx_compile_stdcxx.m4
index 43087b2e..9413da62 100644
--- a/m4/ax_cxx_compile_stdcxx.m4
+++ b/m4/ax_cxx_compile_stdcxx.m4
@@ -16,7 +16,7 @@
 #   The second argument, if specified, indicates whether you insist on an
 #   extended mode (e.g. -std=gnu++11) or a strict conformance mode (e.g.
 #   -std=c++11).  If neither is specified, you get whatever works, with
-#   preference for an extended mode.
+#   preference for no added switch, and then for an extended mode.
 #
 #   The third argument, if specified 'mandatory' or if left unspecified,
 #   indicates that baseline support for the specified C++ standard is
@@ -35,13 +35,14 @@
 #   Copyright (c) 2015 Moritz Klammler <moritz@klammler.eu>
 #   Copyright (c) 2016, 2018 Krzesimir Nowak <qdlacz@gmail.com>
 #   Copyright (c) 2019 Enji Cooper <yaneurabeya@gmail.com>
+#   Copyright (c) 2020 Jason Merrill <jason@redhat.com>
 #
 #   Copying and distribution of this file, with or without modification, are
 #   permitted in any medium without royalty provided the copyright notice
 #   and this notice are preserved.  This file is offered as-is, without any
 #   warranty.
 
-#serial 11
+#serial 12
 
 dnl  This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
 dnl  (serial version number 13).
@@ -62,6 +63,16 @@ AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
   AC_LANG_PUSH([C++])dnl
   ac_success=no
 
+  m4_if([$2], [], [dnl
+    AC_CACHE_CHECK(whether $CXX supports C++$1 features by default,
+		   ax_cv_cxx_compile_cxx$1,
+      [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
+        [ax_cv_cxx_compile_cxx$1=yes],
+        [ax_cv_cxx_compile_cxx$1=no])])
+    if test x$ax_cv_cxx_compile_cxx$1 = xyes; then
+      ac_success=yes
+    fi])
+
   m4_if([$2], [noext], [], [dnl
   if test x$ac_success = xno; then
     for alternative in ${ax_cxx_compile_alternatives}; do