As far as I can tell, the only thing relevant to XS there is

(add-to-list 'auto-mode-alist '("\\.xs\\'" . c-mode))

[download]

which is to say they set files ending in ".xs" to C mode. But XS files aren't C code. A snippet for example: 

# -----------------------------------------

MODULE = Mozilla::DOM    PACKAGE = Mozilla::DOM::NSEvent    PREFIX = m
+oz_dom_

PRBool
moz_dom_DispatchEvent (target, event)
        nsIDOMEventTarget *target;
        nsIDOMEvent *event;
    PREINIT:
        PRBool rv;
    CODE:
        target->DispatchEvent(event, &rv);
        RETVAL = rv;
    OUTPUT:
        RETVAL

[download]

Though at a glance it looks like the syntax highlighting is okay in C mode. It would be neat if there was an XS mode, similar to mmm-mode in that it could use different modes in different regions of the page (e.g. in mmm-mode, the HTML is done differently than the %perl sections; the XS mode could distinguish the C code at the top from the XS code at the bottom).

In reply to Re^2: XS mode for (x)emacs? by ForgotPasswordAgain
in thread XS mode for (x)emacs? by Joost

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