From 0b5cb18b71719d78b228eafd1d29fac592fde86c Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Wed, 21 Sep 2022 17:11:43 -0700
Subject: [PATCH] Use buffering in to_string to avoid bloat

---
 include/fmt/format-inl.h |  5 ++---
 include/fmt/format.h     | 10 +++++-----
 test/format-test.cc      |  7 ++-----
 3 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index 2d3a4d61..eadf0da3 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -1444,9 +1444,8 @@ template <> struct formatter<detail::bigint> {
     return ctx.begin();
   }
 
-  template <typename FormatContext>
-  auto format(const detail::bigint& n, FormatContext& ctx) const ->
-      typename FormatContext::iterator {
+  auto format(const detail::bigint& n, format_context& ctx) const
+      -> format_context::iterator {
     auto out = ctx.out();
     bool first = true;
     for (auto i = n.bigits_.size(); i > 0; --i) {
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 4b26f926..f1757531 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -3426,8 +3426,8 @@ template <typename Char, typename OutputIt, typename T,
 FMT_CONSTEXPR auto write(OutputIt out, const T& value) -> enable_if_t<
     std::is_class<T>::value && !is_string<T>::value &&
         !is_floating_point<T>::value && !std::is_same<T, Char>::value &&
-        !std::is_same<const T&,
-                      decltype(arg_mapper<Context>().map(value))>::value,
+        !std::is_same<T, remove_cvref_t<decltype(arg_mapper<Context>().map(
+                             value))>>::value,
     OutputIt> {
   return write<Char>(out, arg_mapper<Context>().map(value));
 }
@@ -4106,9 +4106,9 @@ auto join(Range&& range, string_view sep)
  */
 template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
 inline auto to_string(const T& value) -> std::string {
-  auto result = std::string();
-  detail::write<char>(std::back_inserter(result), value);
-  return result;
+  auto buffer = memory_buffer();
+  detail::write<char>(appender(buffer), value);
+  return {buffer.data(), buffer.size()};
 }
 
 template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
diff --git a/test/format-test.cc b/test/format-test.cc
index 27a21303..4db3c9c4 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1970,8 +1970,7 @@ template <typename, typename OutputIt> void write(OutputIt, foo) = delete;
 FMT_BEGIN_NAMESPACE
 template <>
 struct formatter<adl_test::fmt::detail::foo> : formatter<std::string> {
-  template <typename FormatContext>
-  auto format(adl_test::fmt::detail::foo, FormatContext& ctx)
+  auto format(adl_test::fmt::detail::foo, format_context& ctx)
       -> decltype(ctx.out()) {
     return formatter<std::string>::format("foo", ctx);
   }
@@ -1979,9 +1978,7 @@ struct formatter<adl_test::fmt::detail::foo> : formatter<std::string> {
 FMT_END_NAMESPACE
 
 struct convertible_to_int {
-  operator int() const { return value; }
-
-  int value = 42;
+  operator int() const { return 42; }
 };
 
 TEST(format_test, to_string) {