https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81310
--- Comment #2 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- It's valid on variables (but hidden aliases to variables in shared libraries don't work properly, and the static linker has special handling for the case where a shared library exports both variable __foo and a weak alias foo, to ensure that works properly both for programs that only reference foo and for programs that define their own foo).
