From fc429d18b6d3c7587ae66cce27504871d4f49962 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Mon, 11 Apr 2022 16:52:34 -0700
Subject: [PATCH] Avoid overhead on sensible platforms

---
 include/fmt/ostream.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/fmt/ostream.h b/include/fmt/ostream.h
index b35725a3..b77bd9a7 100644
--- a/include/fmt/ostream.h
+++ b/include/fmt/ostream.h
@@ -93,8 +93,9 @@ inline bool write(std::wfilebuf&, fmt::basic_string_view<wchar_t>) {
 // It is a separate function rather than a part of vprint to simplify testing.
 template <typename Char>
 void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
-  if (auto filebuf = dynamic_cast<std::basic_filebuf<Char>*>(os.rdbuf())) {
-    if (write(*filebuf, {buf.data(), buf.size()})) return;
+  if (FMT_MSC_VER) {
+    auto filebuf = dynamic_cast<std::basic_filebuf<Char>*>(os.rdbuf());
+    if (filebuf && write(*filebuf, {buf.data(), buf.size()})) return;
   }
   const Char* buf_data = buf.data();
   using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;