libstdc++: Use unsigned char argument to std::isdigit

Passing plain char to isdigit is undefined if the value is negative.

libstdc++-v3/ChangeLog:

	* include/std/charconv (__from_chars_alnum): Pass unsigned
	char to std::isdigit.

diff --git a/libstdc++-v3/include/std/charconv b/libstdc++-v3/include/std/charconv
index 193702e677a6af0c857e79a4a620d01227f4c1c2..571be075a6b35dd73407646945cbdbd875516751 100644 (file)
--- a/libstdc++-v3/include/std/charconv
+++ b/libstdc++-v3/include/std/charconv
@@ -565,7 +565,7 @@ namespace __detail
       while (__first != __last)
        {
          unsigned char __c = *__first;
-         if (std::isdigit(__c))
+         if (std::isdigit(static_cast<unsigned char>(__c)))
            __c -= '0';
          else
            {