[PATCH] libstdc++: Fix check for 7-bit ASCII characters

[Jonathan Wakely]

This should check for c <= 0x7f not x < 0x7f, because 0x7f is an ASCII
character (DEL).

libstdc++-v3/ChangeLog:

	* include/bits/unicode.h (__is_single_code_unit): Fix check for
	7-bit ASCII characters.
---

Tested x86_64-linux.

There's no new test for this as I couldn't get std::format to produce
wrong results with e.g. DEL as a fill character. It gives the right
result, just using a slower path that converts the fill character to
UTF-32 and then constructs a basic_string from _Utf32_view. With the
fix, we avoid that slow path.

 libstdc++-v3/include/bits/unicode.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/unicode.h b/libstdc++-v3/include/bits/unicode.h
index 88e97d41a9eb..00efbe89ca8e 100644
--- a/libstdc++-v3/include/bits/unicode.h
+++ b/libstdc++-v3/include/bits/unicode.h
@@ -61,7 +61,7 @@ namespace __unicode
     __is_single_code_unit(char32_t __c)
     {
       if constexpr (__gnu_cxx::__int_traits<_CharT>::__max <= 0xFF)
-	return __c < 0x7F; // ASCII character
+	return __c <= 0x7F; // ASCII character
       else
 	return __c < __gnu_cxx::__int_traits<_CharT>::__max
 		       && __is_scalar_value(__c);
-- 
2.51.0