[Fontconfig] Re: Bug in fc-cat with user cache

[Mike FABIAN]

Patrick Lam <plam at MIT.EDU> さんは書きました:

> Mike FABIAN wrote:
>> Yes, I can confirm that it is still incorrect like Frederic writes.
>> What was wrong with my attached patch? I'm not sure
>> but I think something similar is necessary. 	    if
>> (!FcDirCacheConsume (cache->fd, dir, set, config))
>> always adds the top-level directory to the list of directories
>> which is then used in FcConfigNormalizeFontDir(). For example it adds
>> the same directory /usr/X11R6/lib/X11/fonts/ many times but never
>> the subdirectories like /usr/X11R6/lib/X11/fonts/Type1/ ...
>> Replacing "dir" by "d->name" like
>> 	    if (!FcDirCacheConsume (cache->fd, d->name, set, config))
>> seems to fix this because now the correct directory names area added
>> to the list.
>
> I don't think it should be necessary if you don't normalize the path
> in the outer fc-cat loop, because you have to treat the directory
> anyway before you can emit the cache, which should cause the proper
> directory to be added to fontDirs.  Clearly the present code is
> incorrect, and I'll look at it (since I'm now back in civilization),
> but I think that we can avoid the issues involved with your patch.
>
> Also, if d->name and dir don't match, there's something wrong...

Then why is the comparison done like this in FcGlobalCacheReadDir():

    if (strncmp (d->name, dir, strlen(dir)) == 0)

?

That checks whether "d->name" is a subdirectory of "dir".

If "d->name" and "dir" have to match here, the comparison
should be

    if (strcmp (d->name, dir) == 0)

But then it would almost always fail, except for the top-level
directory.

Can't you reproduce the following problem?:

First delete all caches:

    root at magellan:~# pwd
    /root
    root at magellan:~# rm -f .fonts.cache-2 
    root at magellan:~# rm -f /var/cache/fontconfig/*cache*
    root at magellan:~#

Now call fc-match which generates the user specific cache
/root/.fonts.cache-2:

    root at magellan:~# fc-match -v "Luxi Mono" 
    Pattern has 29 elts (size 32)
            family: "Luxi Mono"(s)
            familylang: "en"(s)
            style: "Regular"(s)
            stylelang: "en"(s)
            slant: 0(i)(s)
            weight: 80(i)(s)
            width: 100(i)(s)
            size: 12(f)(s)
            pixelsize: 12.5(f)(s)
            spacing: 100(i)(s)
            foundry: "b&h"(s)
            antialias: FcTrue(w)
            hintstyle: 3(i)(s)
            hinting: FcTrue(s)
            verticallayout: FcFalse(s)
            autohint: FcTrue(w)
            globaladvance: FcTrue(s)
            file: "/usr/X11R6/lib/X11/fonts/truetype/luximr.ttf"(s)
            index: 0(i)(s)
            outline: FcTrue(s)
            scalable: FcTrue(s)
            dpi: 75(f)(s)
            rgba: 0(i)(w)
            scale: 1(f)(s)
            charset: set(s)
            lang: aa|af|ast|ay|bi|br|ca|ch|co|cs|da|et|eu|fj|fo|fr|fur|fy|gd|gl|gv|ho|hu|ia|id|ie|io|is|kl|lb|mg|mt|nb|nds|nn|no|oc|om|pl|rm|se|sk|sma|smj|smn|so|sq|sv|sw|tn|tr|ts|vo|wa|wen|wo|xh|yap|zu(s)
            fontversion: 78643(i)(s)
            fontformat: "TrueType"(s)
            embeddedbitmap: FcFalse(w)

    root at magellan:~#

Note that the full path to the font file listed here is correct!

But now call the fc-match once again with the same arguments:

    root at magellan:~# fc-match -v "Luxi Mono" 
    Pattern has 29 elts (size 32)
            family: "Luxi Mono"(s)
            familylang: "en"(s)
            style: "Regular"(s)
            stylelang: "en"(s)
            slant: 0(i)(s)
            weight: 80(i)(s)
            width: 100(i)(s)
            size: 12(f)(s)
            pixelsize: 12.5(f)(s)
            spacing: 100(i)(s)
            foundry: "b&h"(s)
            antialias: FcTrue(w)
            hintstyle: 3(i)(s)
            hinting: FcTrue(s)
            verticallayout: FcFalse(s)
            autohint: FcTrue(w)
            globaladvance: FcTrue(s)
            file: "/usr/X11R6/lib/X11/fonts/luximr.ttf"(s)
            index: 0(i)(s)
            outline: FcTrue(s)
            scalable: FcTrue(s)
            dpi: 75(f)(s)
            rgba: 0(i)(w)
            scale: 1(f)(s)
            charset: set(s)
            lang: aa|af|ast|ay|bi|br|ca|ch|co|cs|da|et|eu|fj|fo|fr|fur|fy|gd|gl|gv|ho|hu|ia|id|ie|io|is|kl|lb|mg|mt|nb|nds|nn|no|oc|om|pl|rm|se|sk|sma|smj|smn|so|sq|sv|sw|tn|tr|ts|vo|wa|wen|wo|xh|yap|zu(s)
            fontversion: 78643(i)(s)
            fontformat: "TrueType"(s)
            embeddedbitmap: FcFalse(w)

    root at magellan:~# 

The full path to the font file listed now is incorrect, it lacks
the final subdirectory.

>From now on it will stay like that and all applications using
fontconfig will crash.

-- 
Mike FABIAN   <mfabian at suse.de>   http://www.suse.de/~mfabian
睡眠不足はいい仕事の敵だ。