Fix recursion check in range formatting

fmtlib · Mar 4, 2023 · e0748e6 · e0748e6
1 parent b94e101
commit e0748e6
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Showing 2 changed files with 17 additions and 11 deletions.
diff --git a/include/fmt/ranges.h b/include/fmt/ranges.h
@@ -505,13 +505,14 @@ struct range_formatter<
 enum class range_format { disabled, map, set, sequence, string, debug_string };
 
 namespace detail {
-template <typename T> struct range_format_kind_ {
-  static constexpr auto value = std::is_same<range_reference_type<T>, T>::value
-                                    ? range_format::disabled
-                                : is_map<T>::value ? range_format::map
-                                : is_set<T>::value ? range_format::set
-                                                   : range_format::sequence;
-};
+template <typename T>
+struct range_format_kind_
+    : std::integral_constant<range_format,
+                             std::is_same<uncvref_type<T>, T>::value
+                                 ? range_format::disabled
+                             : is_map<T>::value ? range_format::map
+                             : is_set<T>::value ? range_format::set
+                                                : range_format::sequence> {};
 
 template <range_format K, typename R, typename Char, typename Enable = void>
 struct range_default_formatter;

diff --git a/test/ranges-test.cc b/test/ranges-test.cc
@@ -179,15 +179,20 @@ TEST(ranges_test, format_to) {
   EXPECT_STREQ(buf, "[1, 2, 3]");
 }
 
-struct path_like {
+template <typename Char> struct path_like {
   const path_like* begin() const;
   const path_like* end() const;
 
-  operator std::string() const;
+  operator std::basic_string<Char>() const;
 };
 
-TEST(ranges_test, path_like) {
-  EXPECT_FALSE((fmt::is_range<path_like, char>::value));
+TEST(ranges_test, disabled_range_formatting_of_path) {
+  // Range formatting of path is disabled because of infinite recursion
+  // (path element is itself a path).
+  EXPECT_EQ((fmt::range_format_kind<path_like<char>, char>::value),
+            fmt::range_format::disabled);
+  EXPECT_EQ((fmt::range_format_kind<path_like<wchar_t>, char>::value),
+            fmt::range_format::disabled);
 }
 
 // A range that provides non-const only begin()/end() to test fmt::join