Support alternative locale names in tests

include/fmt/chrono.h

@@ -1141,7 +1141,7 @@ template <> struct formatter<weekday> {
     if (end.failed()) FMT_THROW(format_error("failed to format time"));
     auto s = os.str();
     if (detail::is_utf8() && localized) {
-      // char16_t codecvt is broken in MSVC.
+      // char16_t and char32_t codecvts are broken in MSVC (linkage errors).
       using code_unit = conditional_t<FMT_MSC_VER, wchar_t, char16_t>;
       auto& f =
           std::use_facet<std::codecvt<code_unit, char, std::mbstate_t>>(loc);

test/unicode-test.cc

@@ -5,6 +5,8 @@
 //
 // For the license information refer to format.h.
 
+#include <iomanip>
+#include <locale>
 #include <vector>
 
 #include "fmt/chrono.h"
@@ -16,14 +18,31 @@ using testing::Contains;
 TEST(unicode_test, is_utf8) { EXPECT_TRUE(fmt::detail::is_utf8()); }
 
 TEST(unicode_test, legacy_locale) {
-  auto loc = get_locale("ru_RU.CP1251");
+  auto loc = get_locale("ru_RU.CP1251", "Russian.1251");
   if (loc == std::locale::classic()) return;
+
+  auto s = std::string();
   try {
-    EXPECT_THAT(
+    s = fmt::format(loc, "День недели: {:L}", fmt::weekday(1));
-        (std::vector<std::string>{"День недели: пн", "День недели: Пн"}),
-        Contains(fmt::format(loc, "День недели: {:L}", fmt::weekday(1))));
   } catch (const fmt::format_error& e) {
-    // Formatting can fail due to unsupported encoding.
+    // Formatting can fail due to an unsupported encoding.
     fmt::print("Format error: {}\n", e.what());
+    return;
   }
+
+#if !FMT_GCC_VERSION || FMT_GCC_VERSION >= 500
+  auto&& os = std::ostringstream();
+  os.imbue(loc);
+  auto tm = std::tm();
+  tm.tm_wday = 1;
+  os << std::put_time(&tm, "%a");
+  auto wd = os.str();
+  if (wd == "??") {
+    EXPECT_EQ(s, "День недели: ??");
+    fmt::print("std::locale gives ?? as a weekday.\n");
+    return;
+  }
+#endif
+  EXPECT_THAT((std::vector<std::string>{"День недели: пн", "День недели: Пн"}),
+              Contains(s));
 }

test/util.cc

@@ -27,11 +27,20 @@ fmt::buffered_file open_buffered_file(FILE** fp) {
   return f;
 }
 
-std::locale get_locale(const char* name) {
+std::locale do_get_locale(const char* name) {
   try {
     return std::locale(name);
   } catch (const std::runtime_error&) {
-    fmt::print(stderr, "{} locale is missing.\n", name);
   }
   return std::locale::classic();
 }
+
+std::locale get_locale(const char* name, const char* alt_name) {
+  auto loc = do_get_locale(name);
+  if (loc == std::locale::classic() && alt_name) {
+    loc = do_get_locale(alt_name);
+  }
+  if (loc == std::locale::classic())
+    fmt::print(stderr, "{} locale is missing.\n", name);
+  return loc;
+}

test/util.h

@@ -78,4 +78,4 @@ class date {
 };
 
 // Returns a locale with the given name if available or classic locale othewise.
-std::locale get_locale(const char* name);
+std::locale get_locale(const char* name, const char* alt_name = nullptr);