libstdc++: Make __from_chars_alnum_to_val conversion explicit

The optimizations from commit r12-8175-ga54137c88061c7 introduced a
clang integer sanitizer error.

Fix this with an explicit static_cast, similar to the fix for PR 96766.

libstdc++-v3/ChangeLog:

	* include/std/charconv (__from_chars_alnum_to_val): Replace
	implicit conversion from int to unsigned char with explicit
	cast.

(cherry picked from commit 20ab3972240aff596a3fa98e9fb09ddc0658fbb3)

diff --git a/libstdc++-v3/include/std/charconv b/libstdc++-v3/include/std/charconv
index 218813e4797f3a02de57e41f2bea462d855beec9..533320ea08521982eafc82511e75fc733a7265eb 100644 (file)
--- a/libstdc++-v3/include/std/charconv
+++ b/libstdc++-v3/include/std/charconv
@@ -436,7 +436,7 @@ namespace __detail
     __from_chars_alnum_to_val(unsigned char __c)
     {
       if _GLIBCXX17_CONSTEXPR (_DecOnly)
-       return __c - '0';
+       return static_cast<unsigned char>(__c - '0');
       else
        {
          // This initializer is deliberately made dependent in order to work