Add compilation support with Newlib nano for embedded targets

Remove the dependency on std::locale to reduce executable sizes

For embedded target the usage of locale bring a huge amount of code to the executable, just to get hold of the thousands separator. Using a static defined thousands separator makes libfmt embedded target friendly.

include/fmt/format-inl.h

@@ -18,7 +18,9 @@
 #include <cmath>
 #include <cstdarg>
 #include <cstddef>  // for std::ptrdiff_t
-#include <locale>
+#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
+# include <locale>
+#endif
 
 #if defined(_WIN32) && defined(__MINGW32__)
 # include <cstring>
@@ -193,6 +195,7 @@ void report_error(FormatFunc func, int error_code,
 }
 }  // namespace
 
+#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
 class locale {
  private:
   std::locale locale_;
@@ -217,6 +220,12 @@ FMT_FUNC Char internal::thousands_sep(locale_provider *lp) {
   std::locale loc = lp ? lp->locale().get() : std::locale();
   return std::use_facet<std::numpunct<Char>>(loc).thousands_sep();
 }
+#else
+template <typename Char>
+FMT_FUNC Char internal::thousands_sep(locale_provider *lp) {
+  return FMT_STATIC_THOUSANDS_SEPARATOR;
+}
+#endif
 
 FMT_FUNC void system_error::init(
     int err_code, string_view format_str, format_args args) {
@@ -569,8 +578,9 @@ FMT_FUNC void vprint_rgb(rgb fd, rgb bg, string_view format, format_args args) {
   std::fputs(internal::data::RESET_COLOR, stdout);
 }
 #endif
-
+#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
 FMT_FUNC locale locale_provider::locale() { return fmt::locale(); }
+#endif
 
 FMT_END_NAMESPACE
 

include/fmt/posix.h

@@ -266,7 +266,8 @@ class file {
 long getpagesize();
 
 #if (defined(LC_NUMERIC_MASK) || defined(_MSC_VER)) && \
-    !defined(__ANDROID__) && !defined(__CYGWIN__) && !defined(__OpenBSD__)
+    !defined(__ANDROID__) && !defined(__CYGWIN__) && !defined(__OpenBSD__) && \
+    !defined(__NEWLIB_H__)
 # define FMT_LOCALE
 #endif