Add backport compatibility for non-C++17 (2022-11-13)

Makefile

@@ -11,6 +11,15 @@ CXX ?= $(CXXPREFIX)g++$(CXXSUFFIX)
 # Check compiler support for some functions
 RESULT_HAS_NP_FUNCTIONS := $(shell $(CXX) -o npfunc checks/npfunc.cpp -pthread 2> /dev/null ; echo $$? ; rm -rf npfunc)
 RESULT_HAS_ATOMIC_FUNCTIONS := $(shell $(CXX) -o atomic checks/atomic.cpp 2> /dev/null ; echo $$? ; rm -rf atomic)
+RESULT_HAS_STRING_VIEW := $(shell $(CXX) -std=c++17 -o string_view checks/string_view.cpp -pthread 2> /dev/null ; echo $$? ; rm -rf string_view)
+RESULT_HAS_AUTO_TUPLE := $(shell $(CXX) -std=c++17 -o auto_tuple checks/auto_tuple.cpp -pthread 2> /dev/null ; echo $$? ; rm -rf auto_tuple)
+
+# Enable Backport mode (ancient compilers previous to C++17)
+ifeq "$(RESULT_HAS_STRING_VIEW)" "1"
+  CFLAGS += -isystem nonstd -DNEED_BACKPORT
+else ifeq "$(RESULT_HAS_AUTO_TUPLE)" "1"
+  CFLAGS += -isystem nonstd -DNEED_BACKPORT
+endif
 
 # Includes needed for proper compilation
 INCLUDES +=

checks/auto_tuple.cpp

@@ -0,0 +1,6 @@
+#include <tuple>
+int main(void) {
+  std::tuple<char, int> foo(0,'h');
+  auto [c,i] = foo;
+  return 0;
+}

checks/string_view.cpp

@@ -0,0 +1,7 @@
+#include <string>
+#include <string_view>
+int main(void) {
+  std::string foo("hello");
+  std::string_view sv{foo};
+  return foo == sv;
+}

nonstd/string_view

@@ -0,0 +1,18 @@
+/* string_view
+
+   Free public domain license
+
+   Including string_view_lite from:
+     https://github.com/martinmoene/string-view-lite
+     wget https://raw.githubusercontent.com/martinmoene/string-view-lite/master/include/nonstd/string_view.hpp
+*/
+#ifndef NONSTD__STRING_VIEW_
+#define NONSTD__STRING_VIEW_
+
+#include "string_view.hpp"
+
+namespace std {
+  using string_view = nonstd::string_view;
+}
+
+#endif // NONSTD__STRING_VIEW_