I just upgraded my Emacs build platform to Fedora 30 and found that
Emacs wouldn't build when configured with --enable-gcc-warnings. The
problem is that starting in librsvg 2.45.1, the librsvg functions
rsvg_handle_write and rsvg_handle_close are deprecated, and Emacs calls
those functions. Although I pacified GCC by installing the attached
patch into Emacs master, the underlying problem is still there and an
rsvg expert should take a look at this at some point.