Require C++-11

Includes updates to m4/ax_cxx_compile_stdcxx.m4 to make it work with
msvc, which supports C++-11 with no flags but doesn't set __cplusplus
to a recent value.

1 files changed, 4 insertions, 4 deletions

diff --git a/m4/ax_cxx_compile_stdcxx.m4 b/m4/ax_cxx_compile_stdcxx.m4
index 43087b2e..0aa8eb65 100755..100644
--- a/m4/ax_cxx_compile_stdcxx.m4
+++ b/m4/ax_cxx_compile_stdcxx.m4
@@ -92,7 +92,7 @@ AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
     dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
     dnl Cray's crayCC needs "-h std=c++11"
     for alternative in ${ax_cxx_compile_alternatives}; do
-      for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do
+      for switch in "" -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do
         cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
         AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
                        $cachevar,
@@ -165,7 +165,7 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_11], [[
 
 #error "This is not a C++ compiler"
 
-#elif __cplusplus < 201103L
+#elif __cplusplus < 201103L && ! defined(_MSC_VER)
 
 #error "This is not a C++11 compiler"
 
@@ -456,7 +456,7 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_14], [[
 
 #error "This is not a C++ compiler"
 
-#elif __cplusplus < 201402L
+#elif __cplusplus < 201402L && ! defined(_MSC_VER)
 
 #error "This is not a C++14 compiler"
 
@@ -580,7 +580,7 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[
 
 #error "This is not a C++ compiler"
 
-#elif __cplusplus < 201703L
+#elif __cplusplus < 201703L && ! defined(_MSC_VER)
 
 #error "This is not a C++17 compiler"