From 56c72a671c24434377e619192d485be192ca47b4 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Fri, 2 Sep 2022 09:36:41 -0700
Subject: [PATCH] Reduce locale dependency

---
 .github/workflows/macos.yml |  2 +-
 include/fmt/format-inl.h    |  7 ++++---
 include/fmt/locale.h        | 19 +++++++++++++++----
 test/xchar-test.cc          |  4 ++--
 4 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index 24dd5958..60aee05c 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -7,7 +7,7 @@ permissions:
 
 jobs:
   build:
-    runs-on: macos-10.15
+    runs-on: macos-11
     strategy:
       matrix:
         build_type: [Debug, Release]
diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index c20a323a..88c599cc 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -31,7 +31,7 @@
 #include "locale.h"
 
 FMT_BEGIN_NAMESPACE
-template <typename Char> std::locale::id num_format_facet<Char>::id;
+template <typename Locale> typename Locale::id num_format_facet<Locale>::id;
 
 namespace detail {
 
@@ -131,8 +131,9 @@ FMT_FUNC auto write_int(unsigned long long value, locale_ref loc)
   auto out = std::ostreambuf_iterator<Char>(&buf);
   // We cannot use the num_put<char> facet because it may produce output in
   // a wrong encoding.
-  using facet_t = conditional_t<std::is_same<Char, char>::value,
-                                num_format_facet<>, std::num_put<Char>>;
+  using facet_t =
+      conditional_t<std::is_same<Char, char>::value,
+                    num_format_facet<std::locale>, std::num_put<Char>>;
   if (std::has_facet<facet_t>(locale)) {
     std::use_facet<facet_t>(locale).put(out, ios, ' ', value);
     return buf.str();
diff --git a/include/fmt/locale.h b/include/fmt/locale.h
index 1b22fb47..cc252368 100644
--- a/include/fmt/locale.h
+++ b/include/fmt/locale.h
@@ -8,17 +8,28 @@
 #ifndef FMT_LOCALE_H_
 #define FMT_LOCALE_H_
 
-#include <locale>  // std::num_put
+#include <ios>       // std::ios_base
+#include <iterator>  // std::ostreambuf_iterator
 
 #include "core.h"
 
 FMT_BEGIN_NAMESPACE
 
 // A locale facet that formats numeric values in UTF-8.
-template <typename Char = char>
-class num_format_facet : public std::num_put<Char> {
+template <typename Locale> class num_format_facet : public Locale::facet {
  public:
-  static FMT_API std::locale::id id;
+  static FMT_API typename Locale::id id;
+
+  using iter_type = std::ostreambuf_iterator<char>;
+
+  auto put(iter_type out, std::ios_base& str, char fill,
+           unsigned long long val) const -> iter_type {
+    return do_put(out, str, fill, val);
+  }
+
+ protected:
+  virtual auto do_put(iter_type out, std::ios_base& str, char fill,
+                      unsigned long long val) const -> iter_type = 0;
 };
 
 FMT_END_NAMESPACE
diff --git a/test/xchar-test.cc b/test/xchar-test.cc
index a47a86be..582b3495 100644
--- a/test/xchar-test.cc
+++ b/test/xchar-test.cc
@@ -521,9 +521,9 @@ TEST(locale_test, sign) {
   EXPECT_EQ(fmt::format(std::locale(), L"{:L}", -50), L"-50");
 }
 
-class num_format : public fmt::num_format_facet<> {
+class num_format : public fmt::num_format_facet<std::locale> {
  protected:
-  using fmt::num_format_facet<>::do_put;
+  using fmt::num_format_facet<std::locale>::do_put;
   iter_type do_put(iter_type out, std::ios_base&, char,
                    unsigned long long) const override;
 };