[Fontconfig] [PATCH] fc-list: Exit with an error for invalid patterns

Akira TAGOH akira at tagoh.org
Tue Sep 24 19:09:35 PDT 2013

fc-list is designed to return the errror code only when --quiet option
is set and no fonts matched. otherwise always 0. well, at least at
this moment. so that is the expected behavior and you should see same
result on box where no fonts installed.

On Wed, Sep 25, 2013 at 1:12 AM, W. Trevor King <wking at tremily.us> wrote:
> On Tue, Sep 24, 2013 at 06:01:58PM +0900, Akira TAGOH wrote:
>> On Tue, Sep 24, 2013 at 1:06 PM, W. Trevor King <wking at tremily.us> wrote:
>> > That would be true if FcListPatternMatchAny wasn't an internal
>> > function:
>> >
>> >   $ git --no-pager grep FcListPatternMatchAny
>> >   src/fccfg.c:    if (FcListPatternMatchAny (patterns->fonts[i], font))
>> >   src/fcint.h:FcListPatternMatchAny (const FcPattern *p,
>> >   src/fclist.c:FcListPatternMatchAny (const FcPattern *p,
>> >   src/fclist.c:       if (FcListPatternMatchAny (p,               /* pattern */
>> >
>> > I'm also not sure it makes sense to have different handling for NULL
>> > FcPatterns and non-NULL FcPatterns with no elements, since the comment
>> > for FcListPatternMatchAny says:
>> Talking about NULL FcPattern being introduced by FcNameParse() would
>> means no valid patterns. given that holding that state and calling
>> FcFontList() would ends up to the same result because of no such fonts
>> matched to that pattern. and usually not expecting to see NULL pattern
>> to any APIs. they should use the empty FcPattern instead.
> Ok, it looks like you want different handling for NULL and empty
> patterns.  I was just making sure it was a conscious decision ;).
>> Or applications shouldn't simply continue to work if FcNameParse()
>> failed in this case.
> And that's what the !pat check in fc-match.c, fc-pattern.c, and my
> patch for fc-list.c does ;).  Maybe we want both my patch (actively
> die in fc-list on bad patterns and out-of-memory errors) and yours
> (don't crash if a programmer forgets to check for bad patterns or
> out-of-memory errors)?  One benefit would be that invalid patterns
> return an error code, while the new master does not:
>   $ LD_LIBRARY_PATH=src/.libs/ ./fc-list/.libs/fc-list :charset=xyz
>   $ echo $?
>   0
> since it thinks it successfully searched for the unmatchable NULL
> pattern.
> Cheers,
> Trevor
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