Use standard [[maybe_unused]]

include/exiv2/types.hpp

@@ -40,12 +40,6 @@
  */
 #define EXV_CALL_MEMBER_FN(object,ptrToMember)  ((object).*(ptrToMember))
 
-#ifndef _MSC_VER
-#define EXV_UNUSED [[gnu::unused]]
-#else
-#define EXV_UNUSED
-#endif
-
 // *****************************************************************************
 // forward declarations
 struct tm;

src/canonmn_int.cpp

@@ -437,7 +437,7 @@ namespace Exiv2 {
 
 
     // Categories, tag 0x0023
-    EXV_UNUSED constexpr TagDetails canonCategories[] = {
+    [[maybe_unused]] constexpr TagDetails canonCategories[] = {
         { 0x0001, N_("People")  },
         { 0x0002, N_("Scenery") },
         { 0x0004, N_("Events")  },
@@ -2110,7 +2110,7 @@ namespace Exiv2 {
     };
 
     //! ManualFlashOutput, tag 0x0029
-    EXV_UNUSED constexpr TagDetails canonCsManualFlashOutput[] = {
+    [[maybe_unused]] constexpr TagDetails canonCsManualFlashOutput[] = {
         { 0x0000, N_("n/a")    },
         { 0x0500, N_("Full")   },
         { 0x0502, N_("Medium") },

src/minoltamn_int.cpp

@@ -63,7 +63,7 @@ namespace Exiv2 {
     };
 
     //! Lookup table to translate Minolta image quality values to readable labels
-    EXV_UNUSED constexpr TagDetails minoltaImageQuality[] = {
+    [[maybe_unused]] constexpr TagDetails minoltaImageQuality[] = {
         { 0, N_("Raw")        },
         { 1, N_("Super Fine") },
         { 2, N_("Fine")       },
@@ -273,7 +273,7 @@ namespace Exiv2 {
     };
 
     //! Lookup table to translate Minolta Std camera settings AF points values to readable labels
-    EXV_UNUSED constexpr TagDetails minoltaAFPointsStd[] = {
+    [[maybe_unused]] constexpr TagDetails minoltaAFPointsStd[] = {
         { 0, N_("Center")       },
         { 1, N_("Top")          },
         { 2, N_("Top-right")    },

src/olympusmn_int.cpp

@@ -490,7 +490,7 @@ namespace Exiv2 {
     };
 
     //! FocusMode, tag 0x0301
-    EXV_UNUSED constexpr TagDetails olympusCsFocusMode[] = {
+    [[maybe_unused]] constexpr TagDetails olympusCsFocusMode[] = {
         { 0, N_("Single AF")              },
         { 1, N_("Sequential shooting AF") },
         { 2, N_("Continuous AF")          },