From b7809f91e2cc42d3bb693e742a28815832c6cb89 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@meta.com>
Date: Sat, 11 May 2024 14:50:48 -0700
Subject: [PATCH] Enable Unicode support by default

---
 CMakeLists.txt      | 6 ++++++
 include/fmt/base.h  | 7 +++++--
 test/CMakeLists.txt | 3 +++
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 767d30aa..037b7481 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -341,6 +341,12 @@ endif ()
 add_library(fmt-header-only INTERFACE)
 add_library(fmt::fmt-header-only ALIAS fmt-header-only)
 
+if (MSVC)
+  # Unicode support requires compiling with /utf-8.
+  target_compile_options(fmt PUBLIC /utf-8)
+  target_compile_options(fmt-header-only INTERFACE /utf-8)
+endif ()
+
 target_compile_definitions(fmt-header-only INTERFACE FMT_HEADER_ONLY=1)
 target_compile_features(fmt-header-only INTERFACE cxx_std_11)
 
diff --git a/include/fmt/base.h b/include/fmt/base.h
index d732d6bb..2de369f5 100644
--- a/include/fmt/base.h
+++ b/include/fmt/base.h
@@ -424,8 +424,11 @@ FMT_CONSTEXPR inline auto is_utf8() -> bool {
   FMT_MSC_WARNING(suppress : 4566) constexpr unsigned char section[] = "\u00A7";
   // Avoid an MSVC sign extension bug: https://github.com/fmtlib/fmt/pull/2297.
   using uchar = unsigned char;
-  return FMT_UNICODE || (sizeof(section) == 3 && uchar(section[0]) == 0xC2 &&
-                         uchar(section[1]) == 0xA7);
+  constexpr bool utf8 = sizeof(section) == 3 && uchar(section[0]) == 0xC2 &&
+                        uchar(section[1]) == 0xA7;
+  static_assert(utf8 || !FMT_MSC_VERSION,
+                "Unicode support requires compiling with /utf-8");
+  return FMT_UNICODE || utf8;
 }
 
 template <typename Char> FMT_CONSTEXPR auto length(const Char* s) -> size_t {
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 0e903dd9..6f7214a8 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -146,6 +146,9 @@ if (NOT MSVC_STATIC_RUNTIME)
   if (FMT_PEDANTIC)
     target_compile_options(posix-mock-test PRIVATE ${PEDANTIC_COMPILE_FLAGS})
   endif ()
+  if (MSVC)
+    target_compile_options(posix-mock-test PRIVATE /utf-8)
+  endif ()
   add_test(NAME posix-mock-test COMMAND posix-mock-test)
   add_fmt_test(os-test)
 endif ()