support platforms without wchar_t

closes #51

include/boost/static_string/config.hpp

@@ -239,6 +239,24 @@ defined(BOOST_STATIC_STRING_CPP14)
 #define BOOST_STATIC_STRING_GCC5_BAD_CONSTEXPR
 #endif
 
+#ifndef BOOST_STATIC_STRING_STANDALONE
+#if ! defined(BOOST_NO_CWCHAR) && ! defined(BOOST_NO_SWPRINTF)
+#define BOOST_STATIC_STRING_HAS_WCHAR
+#endif
+#else
+#ifndef __has_include
+// If we don't have __has_include in standalone,
+// we will assume that <cwchar> exists.
+#define BOOST_STATIC_STRING_HAS_WCHAR
+#elif __has_include(<cwchar>)
+#define BOOST_STATIC_STRING_HAS_WCHAR
+#endif
+#endif
+
+#ifdef BOOST_STATIC_STRING_HAS_WCHAR
+#include <cwchar>
+#endif
+
 // Define the basic string_view type used by the library
 // Conversions to and from other available string_view types
 // are still defined.

include/boost/static_string/static_string.hpp

@@ -34,7 +34,6 @@
 #include <algorithm>
 #include <cstdint>
 #include <cstdio>
-#include <cwchar>
 #include <functional>
 #include <initializer_list>
 #include <limits>
@@ -58,9 +57,11 @@ template<std::size_t N>
 using static_string =
   basic_static_string<N, char, std::char_traits<char>>;
 
+#ifdef BOOST_STATIC_STRING_HAS_WCHAR
 template<std::size_t N>
 using static_wstring =
   basic_static_string<N, wchar_t, std::char_traits<wchar_t>>;
+#endif
 
 template<std::size_t N>
 using static_u16string =
@@ -555,6 +556,7 @@ to_static_string_int_impl(Integer value) noexcept
   return static_string<N>(digits_begin, std::distance(digits_begin, digits_end));
 }
 
+#ifdef BOOST_STATIC_STRING_HAS_WCHAR
 template<std::size_t N, typename Integer>
 inline
 static_wstring<N>
@@ -566,6 +568,7 @@ to_static_wstring_int_impl(Integer value) noexcept
     digits_end, value, std::is_signed<Integer>{});
   return static_wstring<N>(digits_begin, std::distance(digits_begin, digits_end));
 }
+#endif
 
 BOOST_STATIC_STRING_CPP11_CONSTEXPR
 inline
@@ -643,6 +646,7 @@ to_static_string_float_impl(long double value) noexcept
   return static_string<N>(buffer);
 }
 
+#ifdef BOOST_STATIC_STRING_HAS_WCHAR
 template<std::size_t N>
 inline
 static_wstring<N>
@@ -716,6 +720,7 @@ to_static_wstring_float_impl(long double value) noexcept
   // this will not throw
   return static_wstring<N>(buffer);
 }
+#endif
 
 #if defined(__GNUC__) && __GNUC__ >= 7
 #pragma GCC diagnostic pop
@@ -6227,6 +6232,7 @@ to_static_string(long double value) noexcept
     std::numeric_limits<long double>::max_digits10 + 4>(value);
 }
 
+#ifdef BOOST_STATIC_STRING_HAS_WCHAR
 /// Converts `value` to a `static_wstring`
 static_wstring<std::numeric_limits<int>::digits10 + 2>
 inline
@@ -6307,6 +6313,7 @@ to_static_wstring(long double value) noexcept
   return detail::to_static_wstring_float_impl<
     std::numeric_limits<long double>::max_digits10 + 4>(value);
 }
+#endif
 
 //------------------------------------------------------------------------------
 //
@@ -6347,7 +6354,9 @@ hash_value(
 //------------------------------------------------------------------------------
 
 using static_strings::static_string;
+#ifdef BOOST_STATIC_STRING_HAS_WCHAR
 using static_strings::static_wstring;
+#endif
 using static_strings::static_u16string;
 using static_strings::static_u32string;
 } // boost