Revert "Added support for format string containing '\0' in _format udl (#619) (#620)"

This reverts commit 3aaa25fa for
reasons discussed in #622.

include/fmt/format.h

@@ -3236,7 +3236,7 @@ class udl_formatter {
 # else
 template <typename Char>
 struct udl_formatter {
-  basic_string_view<Char> str;
+  const Char *str;
 
   template <typename... Args>
   auto operator()(Args && ... args) const
@@ -3277,9 +3277,9 @@ constexpr internal::udl_formatter<Char, CHARS...> operator""_format() {
   \endrst
  */
 inline internal::udl_formatter<char>
-operator"" _format(const char *s, std::size_t n) { return {{s, n}}; }
+operator"" _format(const char *s, std::size_t) { return {s}; }
 inline internal::udl_formatter<wchar_t>
-operator"" _format(const wchar_t *s, std::size_t n) { return {{s, n}}; }
+operator"" _format(const wchar_t *s, std::size_t) { return {s}; }
 # endif // FMT_UDL_TEMPLATE
 
 /**

test/format-test.cc

@@ -1469,11 +1469,6 @@ TEST(LiteralsTest, Format) {
   EXPECT_EQ(format("{}c{}", "ab", 1), udl_format);
   auto udl_format_w = L"{}c{}"_format(L"ab", 1);
   EXPECT_EQ(format(L"{}c{}", L"ab", 1), udl_format_w);
-  
-  auto udl_format_null_char = "{}c\0d{}"_format("ab", 1);
-  EXPECT_EQ(format("{}c\0d{}", "ab", 1), udl_format_null_char);
-  auto udl_format_w_null_char = L"{}c\0d{}"_format(L"ab", 1);
-  EXPECT_EQ(format(L"{}c\0d{}", L"ab", 1), udl_format_w_null_char);
 }
 
 TEST(LiteralsTest, NamedArg) {
@@ -1534,7 +1529,6 @@ TEST(FormatTest, CustomArgFormatter) {
 
 TEST(FormatTest, NonNullTerminatedFormatString) {
   EXPECT_EQ("42", format(string_view("{}foo", 2), 42));
-  EXPECT_EQ("42f\0oo", format(string_view("{}f\0oo", 6), 42));
 }
 
 struct variant {