From d08ff53e612c18e7cc3622b0ffb9476353b9d9d9 Mon Sep 17 00:00:00 2001
From: Roelf-Jilling <r-j.wolthuis@live.com>
Date: Tue, 14 Jan 2020 17:38:42 +0100
Subject: [PATCH] Use [[maybe_unused]] with C++17

---
 tests/CMakeLists.txt | 18 +++++++++++++-----
 tests/span_tests.cpp | 12 ++++++++++--
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 1d74c45..973403f 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -57,9 +57,11 @@ if(MSVC) # MSVC or simulating MSVC
           -Wno-missing-prototypes
           -Wno-shift-sign-overflow # GTest gtest-port.h
           -Wno-undef # GTest
-          -Wno-unused-variable
           -Wno-used-but-marked-unused # GTest EXPECT_DEATH
-          $<$<EQUAL:${GSL_CXX_STANDARD},14>:-Wno-unused-member-function>
+          $<$<EQUAL:${GSL_CXX_STANDARD},14>: # no support for [[maybe_unused]]
+            -Wno-unused-member-function
+            -Wno-unused-variable
+          >
         >
     )
 else()
@@ -85,16 +87,22 @@ else()
           -Wno-missing-prototypes
           -Wno-padded
           -Wno-unknown-attributes
-          -Wno-unused-variable
           -Wno-used-but-marked-unused # GTest EXPECT_DEATH
-          $<$<EQUAL:${GSL_CXX_STANDARD},14>:-Wno-unused-member-function>
           -Wno-weak-vtables
+          $<$<EQUAL:${GSL_CXX_STANDARD},14>: # no support for [[maybe_unused]]
+            -Wno-unused-member-function
+            -Wno-unused-variable
+          >
         >
         $<$<CXX_COMPILER_ID:Clang>:
           $<$<CXX_COMPILER_VERSION:5.0.2>:-Wno-undefined-func-template>
         >
         $<$<CXX_COMPILER_ID:GNU>:
-          -Wno-unused-variable
+          $<$<NOT:$<VERSION_LESS:$<CXX_COMPILER_VERSION>,6>>:
+            $<$<EQUAL:${GSL_CXX_STANDARD},14>: # no support for [[maybe_unused]]
+              -Wno-unused-variable
+            >
+          >
         >
     )
 endif(MSVC)
diff --git a/tests/span_tests.cpp b/tests/span_tests.cpp
index d0da49d..20c8bc0 100644
--- a/tests/span_tests.cpp
+++ b/tests/span_tests.cpp
@@ -1287,7 +1287,11 @@ TEST(span_test, from_array_constructor)
 
          auto beyond = s.rend();
          EXPECT_TRUE(it != beyond);
-         EXPECT_DEATH(auto _ = *beyond , deathstring);
+#if (__cplusplus > 201402L)
+        EXPECT_DEATH([[maybe_unused]] auto _ = *beyond , deathstring);
+#else
+        EXPECT_DEATH(auto _ = *beyond , deathstring);
+#endif
 
          EXPECT_TRUE(beyond - first == 4);
          EXPECT_TRUE(first - first == 0);
@@ -1332,7 +1336,11 @@ TEST(span_test, from_array_constructor)
 
          auto beyond = s.crend();
          EXPECT_TRUE(it != beyond);
-         EXPECT_DEATH(auto _ = *beyond, deathstring);
+#if (__cplusplus > 201402L)
+        EXPECT_DEATH([[maybe_unused]] auto _ = *beyond, deathstring);
+#else
+        EXPECT_DEATH(auto _ = *beyond, deathstring);
+#endif
 
          EXPECT_TRUE(beyond - first == 4);
          EXPECT_TRUE(first - first == 0);