better test of compiler capabilities

config-tests/boost-regex-test.cpp

-#include <boost/regex.hpp>
-
-int main()
-{
-  boost::regex rx("a*b");
-
-  if (boost::regex_match("aab", rx))
-    ;
-  return 0;
-}

config-tests/clipper-test.cpp

-#include <clipper/core/atomsf.h>
-
-int main()
-{
-  auto sf = clipper::ScatteringFactors::instance()["C"];
-  return 0;
-}

config-tests/cpp-17-test.cpp

+#include <algorithm>
+
+template<typename COMP>
+class foo
+{
+  public:
+	foo(int a, COMP&& b)
+		: m_a(a), m_b(std::move(b)) {}
+	
+	int m_a;
+	COMP m_b;
+};
+
+void bar(const int& b)
+{
+	int c = 1;
+	auto f = new foo(c, [tag = c, b](const int& x)
+		{ x < b; });
+}

configure

@@ -3920,6 +3920,59 @@ ac_config_headers="$ac_config_headers include/cif++/Config.hpp"
 
 
 
 
 
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking compiler standards compliance" >&5
+$as_echo_n "checking compiler standards compliance... " >&6; }
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <algorithm>
+
+
+
+template<typename COMP>
+
+class foo
+
+{
+
+public:
+
+foo(int a, COMP&& b)
+
+: m_a(a), m_b(std::move(b)) {}
+
+
+
+int m_a;
+
+COMP m_b;
+
+};
+
+
+
+void bar(const int& b)
+
+{
+
+int c = 1;
+
+auto f = new foo(c, [tag = c, b](const int& x)
+
+{ x < b; });
+
+}
+
+
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+
+else
+  as_fn_error $? "Your c++ compiler is not capable of compiling libcifpp, please upgrade" "$LINENO" 5
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: \"ok\"" >&5
+$as_echo "\"ok\"" >&6; }
+
 # Find a good install program.  We prefer a C program (faster),
 # Find a good install program.  We prefer a C program (faster),
 # so one script is as good as another.  But avoid the broken or
 # so one script is as good as another.  But avoid the broken or
 # incompatible versions:
 # incompatible versions:

configure.ac

@@ -18,6 +18,12 @@ AC_PREFIX_DEFAULT(/usr/local)
 AC_DEFUN([read_test], [AC_LANG_SOURCE(
 AC_DEFUN([read_test], [AC_LANG_SOURCE(
 	esyscmd(tools/m4esc.sh config-tests/$1))])
 	esyscmd(tools/m4esc.sh config-tests/$1))])
 
 
+AC_MSG_CHECKING([compiler standards compliance])
+AC_COMPILE_IFELSE(
+	[read_test(cpp-17-test.cpp)], [],
+	[AC_MSG_ERROR([Your c++ compiler is not capable of compiling libcifpp, please upgrade])])
+AC_MSG_RESULT(ok)
+
 AC_PROG_INSTALL
 AC_PROG_INSTALL
 AC_ENABLE_STATIC
 AC_ENABLE_STATIC
 AC_DISABLE_SHARED
 AC_DISABLE_SHARED