Move specs to core.h

include/fmt/core.h

@@ -1811,6 +1811,61 @@ namespace align {
 enum type { none, left, right, center, numeric };
 }
 using align_t = align::type;
+namespace sign {
+enum type { none, minus, plus, space };
+}
+using sign_t = sign::type;
+
+namespace detail {
+void throw_format_error(const char* message);
+
+// Workaround an array initialization issue in gcc 4.8.
+template <typename Char> struct fill_t {
+ private:
+  enum { max_size = 4 };
+  Char data_[max_size] = {Char(' '), Char(0), Char(0), Char(0)};
+  unsigned char size_ = 1;
+
+ public:
+  FMT_CONSTEXPR void operator=(basic_string_view<Char> s) {
+    auto size = s.size();
+    if (size > max_size) return throw_format_error("invalid fill");
+    for (size_t i = 0; i < size; ++i) data_[i] = s[i];
+    size_ = static_cast<unsigned char>(size);
+  }
+
+  constexpr size_t size() const { return size_; }
+  constexpr const Char* data() const { return data_; }
+
+  FMT_CONSTEXPR Char& operator[](size_t index) { return data_[index]; }
+  FMT_CONSTEXPR const Char& operator[](size_t index) const {
+    return data_[index];
+  }
+};
+}  // namespace detail
+
+// Format specifiers for built-in and string types.
+template <typename Char> struct basic_format_specs {
+  int width;
+  int precision;
+  char type;
+  align_t align : 4;
+  sign_t sign : 3;
+  bool alt : 1;  // Alternate form ('#').
+  bool localized : 1;
+  detail::fill_t<Char> fill;
+
+  constexpr basic_format_specs()
+      : width(0),
+        precision(-1),
+        type(0),
+        align(align::none),
+        sign(sign::none),
+        alt(false),
+        localized(false) {}
+};
+
+using format_specs = basic_format_specs<char>;
 
 FMT_MODULE_EXPORT_END
 namespace detail {