The issue :

When using Zathura as a viewer, Zathura fails to launch with the default View command defined by auctex in tex.el when both of the following  conditions are true :

- synctex is used

- the .tex file name has spaces in its filename

My config : emacs 25.3.2 auctex 12.1.1 and Zathura 0.3.5 under elementaryos

The problem was reproduced on a fresh install of antergos with emacs 25.3.1 auctex 12.1.1 and Zathura 0.3.9

The possible cause :

In tex.el Zathura is launched with the following parameters when using synctex :

    (mode-io-correlate " --synctex-forward %n:0:%b -x \"emacsclient +%{line} %{input}\""))

%b is the .tex filename, which is unquoted.

The possible solution :

The problem is solved, as far as I can tell, by replacing %b with: \"%b\"

Yours sincerely,

Arach HIRMANPOUR