Fix clang -Wunused-member-function warnings with FMT_MAYBE_UNUSED att…

…ribute. FMT_MAYBE_UNUSED currently expands to the [[maybe_unused]] attribute on C++17. It could be extended to previous language versions with a compiler-specific attribute if required.
fmtlib · Mar 5, 2020 · aa902c3 · aa902c3
1 parent 153f753
commit aa902c3
Show file tree

Hide file tree

Showing 3 changed files with 12 additions and 1 deletion.
diff --git a/include/fmt/core.h b/include/fmt/core.h
@@ -132,6 +132,14 @@
 #  define FMT_NORETURN
 #endif
 
+#ifndef FMT_MAYBE_UNUSED
+#  if FMT_HAS_CPP_ATTRIBUTE(maybe_unused)
+#    define FMT_MAYBE_UNUSED [[maybe_unused]]
+#  else
+#    define FMT_MAYBE_UNUSED
+#  endif
+#endif
+
 #ifndef FMT_DEPRECATED
 #  if (FMT_HAS_CPP_ATTRIBUTE(deprecated) && __cplusplus >= 201402L) || \
       FMT_MSC_VER >= 1900

diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
@@ -86,6 +86,7 @@ FMT_FUNC int safe_strerror(int error_code, char*& buffer,
     }
 
     // Handle the result of GNU-specific version of strerror_r.
+    FMT_MAYBE_UNUSED
     int handle(char* message) {
       // If the buffer is full then the message is probably truncated.
       if (message == buffer_ && strlen(buffer_) == buffer_size_ - 1)
@@ -95,11 +96,13 @@ FMT_FUNC int safe_strerror(int error_code, char*& buffer,
     }
 
     // Handle the case when strerror_r is not available.
+    FMT_MAYBE_UNUSED
     int handle(internal::null<>) {
       return fallback(strerror_s(buffer_, buffer_size_, error_code_));
     }
 
     // Fallback to strerror_s when strerror_r is not available.
+    FMT_MAYBE_UNUSED
     int fallback(int result) {
       // If the buffer is full then the message is probably truncated.
       return result == 0 && strlen(buffer_) == buffer_size_ - 1 ? ERANGE

diff --git a/include/fmt/format.h b/include/fmt/format.h
@@ -3549,7 +3549,7 @@ FMT_END_NAMESPACE
     /* Use a macro-like name to avoid shadowing warnings. */ \
     struct FMT_STRING : fmt::compile_string {                \
       using char_type = fmt::remove_cvref_t<decltype(*s)>;   \
-      __VA_ARGS__ FMT_CONSTEXPR                              \
+      FMT_MAYBE_UNUSED __VA_ARGS__ FMT_CONSTEXPR             \
       operator fmt::basic_string_view<char_type>() const {   \
         /* FMT_STRING only accepts string literals. */       \
         return fmt::internal::literal_to_view(s);            \