Re: [PATCH v3] wildmatch: properly fold case everywhere
--
Anthony Ramine
Le 29 mai 2013 à 15:52, Duy Nguyen a écrit :
> On Wed, May 29, 2013 at 8:37 PM, Anthony Ramine <n.oxyde@gmail.com> wrote:
>> Le 29 mai 2013 à 15:22, Duy Nguyen a écrit :
>>
>>> On Tue, May 28, 2013 at 8:58 PM, Anthony Ramine <n.oxyde@gmail.com> wrote:
>>>> Case folding is not done correctly when matching against the [:upper:]
>>>> character class and uppercased character ranges (e.g. A-Z).
>>>> Specifically, an uppercase letter fails to match against any of them
>>>> when case folding is requested because plain characters in the pattern
>>>> and the whole string and preemptively lowercased to handle the base case
>>>> fast.
>>>
>>> I did a little test with glibc fnmatch and also checked the source
>>> code. I don't think 'a' matches [:upper:]. So I'm not sure if that's a
>>> correct behavior or a bug in glibc. The spec is not clear (I think) on
>>> this. I guess we should just assume that 'a' should match '[:upper:]'?
>>
>> I don't know, in my opinion if case folding is enabled we should say [:upper:], [:lower:] and [:alpha:] are equivalent.
>>
>> This opinion is shared by GNU Flex [1]:
>>
>>> • If your scanner is case-insensitive (the ‘-i’ flag), then ‘[:upper:]’ and ‘[:lower:]’ are equivalent to ‘[:alpha:]’.
>>
>> [1] http://flex.sourceforge.net/manual/Patterns.html
>
> Then we should do it too because of this precedent, I think.
>
>>>> @@ -196,6 +196,11 @@ static int dowild(const uchar *p, const uchar *text, unsigned int flags)
>>>> }
>>>> if (t_ch <= p_ch && t_ch >= prev_ch)
>>>> matched = 1;
>>>> + else if ((flags & WM_CASEFOLD) && ISLOWER(t_ch)) {
>>>> + uchar t_ch_upper = toupper(t_ch);
>>>> + if (t_ch_upper <= p_ch && t_ch_upper >= prev_ch)
>>>> + matched = 1;
>>>> + }
>>>
>>> Or we could stick with to tolower. Something like this
>>>
>>> if ((t_ch <= p_ch && t_ch >= prev_ch) ||
>>> ((flags & WM_CASEFOLD) &&
>>> t_ch <= tolower(p_ch) && t_ch >= tolower(prev_ch)))
>>> match = 1;
>>>
>>> I think it's easier to read if we either downcase all, or upcase all, not both.
>>
>> If the range to match against is [A-_], it will become [a-_] which is an empty range, ord('a') > ord('_'). I think it is simpler to reuse toupper() after the fact as I did.
>>
>> Anyway maybe I should add a test for that corner case?
>
> Yeah I was thinking about such a case, but I saw glibc do it... I
> guess we just found another bug, at least in compat/fnmatch.c. Yes a
> test for it would be great, in case I change my mind 2 years from now
> and decide to turn it the other way ;)
Should I patch compat/fnmatch.c too? That would make it different from the glibc's one.
>>
>>>> p_ch = 0; /* This makes "prev_ch" get set to 0. */
>>>> } else if (p_ch == '[' && p[1] == ':') {
>>>> const uchar *s;
>>>> @@ -245,6 +250,8 @@ static int dowild(const uchar *p, const uchar *text, unsigned int flags)
>>>> } else if (CC_EQ(s,i, "upper")) {
>>>> if (ISUPPER(t_ch))
>>>> matched = 1;
>>>> + else if ((flags & WM_CASEFOLD) && ISLOWER(t_ch))
>>>> + matched = 1;
>>>> } else if (CC_EQ(s,i, "xdigit")) {
>>>> if (ISXDIGIT(t_ch))
>>>> matched = 1;
>>>
>>> If WM_CASEFOLD is set, maybe isalpha(t_ch) is enough then?
>>
>> Yes isalpha() is enought but I wanted to keep the two cases separated, I can amend that if you want.
>
> Either way is fine. I don't think this code is performance critical. Your call.
> --
> DuyAnthony Ramine <n.oxyde@gmail.com>