I just tried (with gcc 9.2.1), and got no warning. As far as I know, these _s versions aren't that good, and often aren't available at all; see http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1967.htm which says among other things
"[...] none of the popular Open Source distribution such as BSD or Linux has chosen to make either available to their users. At least one (GNU C Library) has repeatedly rejected proposals for inclusion [...]"
"[...] As a result of the numerous deviations from the specification the Microsoft implementation cannot be considered conforming or portable."