Move strtod_l check to CMake since it's very system-specific

CMakeLists.txt

@@ -127,11 +127,18 @@ if (MASTER_PROJECT AND CMAKE_GENERATOR MATCHES "Visual Studio")
     ${CMAKE_MAKE_PROGRAM} -p:FrameworkPathOverride=\"${netfxpath}\" %*")
 endif ()
 
+set(strtod_l_headers stdlib.h)
+if (APPLE)
+  set(strtod_l_headers ${strtod_l_headers} xlocale.h)
+endif ()
+
 include(CheckSymbolExists)
 if (WIN32)
   check_symbol_exists(open io.h HAVE_OPEN)
+  check_symbol_exists(_strtod_l "${strtod_l_headers}" HAVE_STRTOD_L)
 else ()
   check_symbol_exists(open fcntl.h HAVE_OPEN)
+  check_symbol_exists(strtod_l "${strtod_l_headers}" HAVE_STRTOD_L)
 endif ()
 
 function(add_headers VAR)
@@ -154,6 +161,10 @@ endif ()
 add_library(fmt ${FMT_SOURCES} ${FMT_HEADERS} README.rst ChangeLog.rst)
 add_library(fmt::fmt ALIAS fmt)
 
+if (HAVE_STRTOD_L)
+  target_compile_definitions(fmt PUBLIC FMT_LOCALE)
+endif ()
+
 if (FMT_WERROR)
   target_compile_options(fmt PRIVATE ${WERROR_FLAG})
 endif ()

include/fmt/posix.h

@@ -261,12 +261,6 @@ class file {
 // Returns the memory page size.
 long getpagesize();
 
-#if (defined(LC_NUMERIC_MASK) || defined(_MSC_VER)) &&                        \
-    !defined(__ANDROID__) && !defined(__CYGWIN__) && !defined(__OpenBSD__) && \
-    !defined(__NEWLIB_H__)
-#  define FMT_LOCALE
-#endif
-
 #ifdef FMT_LOCALE
 // A "C" numeric locale.
 class Locale {

test/CMakeLists.txt

@@ -118,6 +118,9 @@ if (HAVE_OPEN)
   if (FMT_PEDANTIC)
     target_compile_options(posix-mock-test PRIVATE ${PEDANTIC_COMPILE_FLAGS})
   endif ()
+  if (HAVE_STRTOD_L)
+    target_compile_definitions(posix-mock-test PRIVATE FMT_LOCALE)
+  endif ()
   add_test(NAME posix-mock-test COMMAND posix-mock-test)
   add_fmt_test(posix-test)
 endif ()