libstdc++: Add comment to <format> (LWG 3720)

libstdc++-v3/ChangeLog:

	* include/std/format: Add a comment noting that the resolution
	of LWG 3720 has been applied..

diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index b1e627048de956d46c364707b8ccf81654f1ce9c..0e40bce5c15763e4fc8647fe067fa7ad80eb49a3 100644 (file)
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -3119,6 +3119,8 @@ namespace __format
        // 3721. Allow an arg-id with a value of zero for width
        else if constexpr (sizeof(_Tp) <= sizeof(long long))
          {
+           // _GLIBCXX_RESOLVE_LIB_DEFECTS
+           // 3720. Restrict the valid types of arg-id for width and precision
            if constexpr (__is_unsigned_integer<_Tp>::value)
              return __arg;
            else if constexpr (__is_signed_integer<_Tp>::value)