From abc4d755f7fe191061af49ef9a23747b185f83f3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stanislav=20Angelovi=C4=8D?=
 <stanislav.angelovic@protonmail.com>
Date: Mon, 19 Feb 2024 19:49:31 +0100
Subject: [PATCH] fix: conditional use and tests of span (#411)

---
 include/sdbus-c++/Message.h         | 14 ++++++++------
 include/sdbus-c++/TypeTraits.h      |  8 +++++---
 tests/unittests/Message_test.cpp    |  4 ++--
 tests/unittests/TypeTraits_test.cpp |  8 ++++----
 4 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/include/sdbus-c++/Message.h b/include/sdbus-c++/Message.h
index 743604c..db5f658 100644
--- a/include/sdbus-c++/Message.h
+++ b/include/sdbus-c++/Message.h
@@ -36,8 +36,10 @@
 #include <cstdint>
 #include <functional>
 #include <map>
-#if __cplusplus >= 202002L
-#include <span>
+#ifdef __has_include
+#  if __has_include(<span>)
+#    include <span>
+#  endif
 #endif
 #include <string>
 #include <sys/types.h>
@@ -104,7 +106,7 @@ namespace sdbus {
         Message& operator<<(const std::vector<_Element, _Allocator>& items);
         template <typename _Element, std::size_t _Size>
         Message& operator<<(const std::array<_Element, _Size>& items);
-#if __cplusplus >= 202002L
+#ifdef __cpp_lib_span
         template <typename _Element, std::size_t _Extent>
         Message& operator<<(const std::span<_Element, _Extent>& items);
 #endif
@@ -140,7 +142,7 @@ namespace sdbus {
         Message& operator>>(std::vector<_Element, _Allocator>& items);
         template <typename _Element, std::size_t _Size>
         Message& operator>>(std::array<_Element, _Size>& items);
-#if __cplusplus >= 202002L
+#ifdef __cpp_lib_span
         template <typename _Element, std::size_t _Extent>
         Message& operator>>(std::span<_Element, _Extent>& items);
 #endif
@@ -339,7 +341,7 @@ namespace sdbus {
         return *this;
     }
 
-#if __cplusplus >= 202002L
+#ifdef __cpp_lib_span
     template <typename _Element, std::size_t _Extent>
     inline Message& Message::operator<<(const std::span<_Element, _Extent>& items)
     {
@@ -498,7 +500,7 @@ namespace sdbus {
         return *this;
     }
 
-#if __cplusplus >= 202002L
+#ifdef __cpp_lib_span
     template <typename _Element, std::size_t _Extent>
     inline Message& Message::operator>>(std::span<_Element, _Extent>& items)
     {
diff --git a/include/sdbus-c++/TypeTraits.h b/include/sdbus-c++/TypeTraits.h
index e7bc59a..4fd0343 100644
--- a/include/sdbus-c++/TypeTraits.h
+++ b/include/sdbus-c++/TypeTraits.h
@@ -35,8 +35,10 @@
 #include <map>
 #include <memory>
 #include <optional>
-#if __cplusplus >= 202002L
-#include <span>
+#ifdef __has_include
+#  if __has_include(<span>)
+#    include <span>
+#  endif
 #endif
 #include <string>
 #include <tuple>
@@ -399,7 +401,7 @@ namespace sdbus {
         }
     };
 
-#if __cplusplus >= 202002L
+#ifdef __cpp_lib_span
     template <typename _Element, std::size_t _Extent>
     struct signature_of<std::span<_Element, _Extent>>
     {
diff --git a/tests/unittests/Message_test.cpp b/tests/unittests/Message_test.cpp
index 73e792f..c91f230 100644
--- a/tests/unittests/Message_test.cpp
+++ b/tests/unittests/Message_test.cpp
@@ -311,7 +311,7 @@ TEST(AMessage, CanCarryDBusArrayOfNontrivialTypesGivenAsStdArray)
     ASSERT_THAT(dataRead, Eq(dataWritten));
 }
 
-#if __cplusplus >= 202002L
+#ifdef __cpp_lib_span
 TEST(AMessage, CanCarryDBusArrayOfTrivialTypesGivenAsStdSpan)
 {
     auto msg = sdbus::createPlainMessage();
@@ -378,7 +378,7 @@ TEST(AMessage, ThrowsWhenDestinationStdArrayIsTooSmallDuringDeserialization)
     ASSERT_THROW(msg >> dataRead, sdbus::Error);
 }
 
-#if __cplusplus >= 202002L
+#ifdef __cpp_lib_span
 TEST(AMessage, ThrowsWhenDestinationStdSpanIsTooSmallDuringDeserialization)
 {
     auto msg = sdbus::createPlainMessage();
diff --git a/tests/unittests/TypeTraits_test.cpp b/tests/unittests/TypeTraits_test.cpp
index 9f69895..3e7e092 100644
--- a/tests/unittests/TypeTraits_test.cpp
+++ b/tests/unittests/TypeTraits_test.cpp
@@ -88,13 +88,13 @@ namespace
     TYPE(sdbus::ObjectPath)HAS_DBUS_TYPE_SIGNATURE("o")
     TYPE(sdbus::Signature)HAS_DBUS_TYPE_SIGNATURE("g")
     TYPE(sdbus::Variant)HAS_DBUS_TYPE_SIGNATURE("v")
+    TYPE(std::variant<int16_t, std::string>)HAS_DBUS_TYPE_SIGNATURE("v")
     TYPE(sdbus::UnixFd)HAS_DBUS_TYPE_SIGNATURE("h")
     TYPE(sdbus::Struct<bool>)HAS_DBUS_TYPE_SIGNATURE("(b)")
     TYPE(sdbus::Struct<uint16_t, double, std::string, sdbus::Variant>)HAS_DBUS_TYPE_SIGNATURE("(qdsv)")
     TYPE(std::vector<int16_t>)HAS_DBUS_TYPE_SIGNATURE("an")
     TYPE(std::array<int16_t, 3>)HAS_DBUS_TYPE_SIGNATURE("an")
-    TYPE(std::variant<int16_t, std::string>)HAS_DBUS_TYPE_SIGNATURE("v")
-#if __cplusplus >= 202002L
+#ifdef __cpp_lib_span
     TYPE(std::span<int16_t>)HAS_DBUS_TYPE_SIGNATURE("an")
 #endif
     TYPE(SomeEnumClass)HAS_DBUS_TYPE_SIGNATURE("y")
@@ -138,13 +138,13 @@ namespace
                             , sdbus::ObjectPath
                             , sdbus::Signature
                             , sdbus::Variant
+                            , std::variant<int16_t, std::string>
                             , sdbus::UnixFd
                             , sdbus::Struct<bool>
                             , sdbus::Struct<uint16_t, double, std::string, sdbus::Variant>
                             , std::vector<int16_t>
                             , std::array<int16_t, 3>
-                            , std::variant<int16_t, std::string>
-#if __cplusplus >= 202002L
+#ifdef __cpp_lib_span
                             , std::span<int16_t>
 #endif
                             , SomeEnumClass