Decouple <locale> for better compile times

include/fmt/CMakeLists.txt

@@ -1,7 +1,7 @@
 # Define the fmt library, its includes and the needed defines.
 # format.cc is added to FMT_HEADERS for the header-only configuration.
-set(FMT_HEADERS format.h format.cc ostream.h ostream.cc printf.h printf.cc
+set(FMT_HEADERS format.h format.cc locale.h ostream.h ostream.cc printf.h
-                string.h time.h write.h)
+                printf.cc string.h time.h write.h)
 if (HAVE_OPEN)
   set(FMT_HEADERS ${FMT_HEADERS} posix.h)
   set(FMT_SOURCES ${FMT_SOURCES} posix.cc)

include/fmt/format.cc

@@ -26,6 +26,7 @@
  */
 
 #include "fmt/format.h"
+#include "fmt/locale.h"
 
 #include <string.h>
 
@@ -218,6 +219,12 @@ void report_error(FormatFunc func, int error_code,
 }
 }  // namespace
 
+template <typename Char>
+FMT_FUNC Char internal::thousands_sep(const basic_buffer<Char>& buf) {
+  return std::use_facet<std::numpunct<Char>>(buf.locale().get())
+                                            .thousands_sep();
+}
+
 FMT_FUNC void system_error::init(
     int err_code, string_view format_str, format_args args) {
   error_code_ = err_code;
@@ -330,7 +337,7 @@ FMT_FUNC int internal::utf16_to_utf8::convert(wstring_view s) {
 }
 
 FMT_FUNC void windows_error::init(
-    int err_code, string_view format_str, args args) {
+    int err_code, string_view format_str, format_args args) {
   error_code_ = err_code;
   memory_buffer buffer;
   internal::format_windows_error(buffer, err_code, vformat(format_str, args));
@@ -436,6 +443,10 @@ template struct internal::basic_data<void>;
 
 // Explicit instantiations for char.
 
+template locale basic_buffer<char>::locale() const;
+
+template char internal::thousands_sep(const basic_buffer<char>& buf);
+
 template void basic_fixed_buffer<char>::grow(std::size_t);
 
 template void internal::arg_map<context>::init(const format_args &args);
@@ -450,6 +461,10 @@ template int internal::char_traits<char>::format_float(
 
 // Explicit instantiations for wchar_t.
 
+template locale basic_buffer<wchar_t>::locale() const;
+
+template wchar_t internal::thousands_sep(const basic_buffer<wchar_t>& buf);
+
 template class basic_context<wchar_t>;
 
 template void basic_fixed_buffer<wchar_t>::grow(std::size_t);

include/fmt/format.h

@@ -34,7 +34,6 @@
 #include <cstdio>
 #include <cstring>
 #include <limits>
-#include <locale>
 #include <memory>
 #include <stdexcept>
 #include <string>
@@ -491,6 +490,10 @@ struct error_handler {
 };
 }  // namespace internal
 
+// A wrapper around std::locale used to reduce compile times since <locale>
+// is very heavy.
+class locale;
+
 /**
   \rst
   A contiguous memory buffer with an optional growing ability.
@@ -566,7 +569,7 @@ class basic_buffer {
   T &operator[](std::size_t index) { return ptr_[index]; }
   const T &operator[](std::size_t index) const { return ptr_[index]; }
 
-  virtual std::locale locale() const { return std::locale(); }
+  virtual fmt::locale locale() const;
 };
 
 typedef basic_buffer<char> buffer;
@@ -979,6 +982,9 @@ class add_thousands_sep {
   }
 };
 
+template <typename Char>
+Char thousands_sep(const basic_buffer<Char>& buf);
+
 // Formats a decimal unsigned integer value writing into buffer.
 // thousands_sep is a functor that is called after writing each char to
 // add a thousands separator if necessary.
@@ -3352,9 +3358,7 @@ void basic_writer<Char>::write_int(T value, const Spec& spec) {
 
     void on_num() {
       unsigned num_digits = internal::count_digits(abs_value);
-      std::locale loc = writer.buffer_.locale();
+      Char thousands_sep = internal::thousands_sep(writer.buffer_);
-      Char thousands_sep =
-          std::use_facet<std::numpunct<Char>>(loc).thousands_sep();
       fmt::basic_string_view<Char> sep(&thousands_sep, 1);
       unsigned size = static_cast<unsigned>(
             num_digits + sep.size() * ((num_digits - 1) / 3));

include/fmt/locale.h

@@ -0,0 +1,43 @@
+/*
+ Formatting library for C++
+
+ Copyright (c) 2012 - 2016, Victor Zverovich
+ All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+
+ 1. Redistributions of source code must retain the above copyright notice, this
+    list of conditions and the following disclaimer.
+ 2. Redistributions in binary form must reproduce the above copyright notice,
+    this list of conditions and the following disclaimer in the documentation
+    and/or other materials provided with the distribution.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "fmt/format.h"
+#include <locale>
+
+namespace fmt {
+class locale {
+ private:
+  std::locale locale_;
+
+ public:
+  explicit locale(std::locale loc = std::locale()) : locale_(loc) {}
+  std::locale get() { return locale_; }
+};
+
+template <typename T>
+locale basic_buffer<T>::locale() const { return fmt::locale(); }
+}

test/util-test.cc

@@ -37,6 +37,7 @@
 # include <type_traits>
 #endif
 
+#include "fmt/locale.h"
 #include "gmock/gmock.h"
 #include "gtest-extra.h"
 #include "mock-allocator.h"