From: Junio C Hamano <gitster@pobox.com>
To: "René Scharfe" <l.s.r@web.de>
Cc: "Masahiro Yamada" <masahiroy@kernel.org>,
git@vger.kernel.org, "Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>
Subject: Re: [PATCH v2 1/5] git-compat-util: add isblank() and isgraph()
Date: Mon, 27 Feb 2023 11:39:44 -0800 [thread overview]
Message-ID: <xmqqpm9usxrz.fsf@gitster.g> (raw)
In-Reply-To: <36cd059e-c676-2aa2-68d9-41a7b0db57f0@web.de> ("René Scharfe"'s message of "Sun, 26 Feb 2023 19:45:22 +0100")
René Scharfe <l.s.r@web.de> writes:
>> In the previous submission, I just moved isblank() and isgraph() as
>> implemented in wildmatch.c. I knew they were not robust against the
>> pointer increment like isblank(*s++), but I thought it was the same
>> pattern as isprint(), which has the same issue. Unfortunately, it was
>> more controversial than I had expected...
>
> Not sure we need that story in the commit message,...
Usually we encourage people to write as if there were no "previous
iterations". Describe how to reach the best end-result without any
detour, using the experience gained from failed attempts.
> ... but it gave me an idea:
;-)
> ... So it's not so
> easy, however, ...
>
>> This version implements them as inline functions because we ran out
>> all bits in the sane_ctype[] table. This is the same pattern as
>> islower() and isupper().
>
> ... if you remove GIT_SPACE from the definition above you get a
> macro version of isgraph() that uses a single table lookup.
>
> If we're out of bits then isblank() is a good choice to implement
> without a table lookup, as this class only contains two characters
> and two comparisons should be quite fast.
Implementing sane_isblank() plus sane_isgraph() as static inlines is
already not too bad, but if one of them can be made into a simple
table look-up, that indeed is better ;-)
> Stepping back a bit: Is using the unlocalized is* macros in
> wildmatch() safe, i.e. do we get the same results as before
> regardless of locale? Junio's remark in
> https://lore.kernel.org/git/xmqq3579crsd.fsf@gitster.g/ sounds
> convincing to me if we don't care about single-byte code pages
> and require plain ASCII or UTF-8. I think it's a good idea to
> address that point in the commit message.
True. To be honest, I wasn't thinking about non-UTF-8 single-byte
"code pages". In the context of wildmatch, the strings we deal with
mostly interact with the paths on the filesystem. If you interact
with your filesystem in latin-1 that may pose an issue, and even if
(or rather, especially if) we are to declare that it does not matter,
we should document it in the proposed log message.
>
> And adding tests to t/helper/test-ctype.c would be nice.
Very true.
>> +#define isblank(x) sane_isblank(x)
>> +#define isgraph(x) sane_isgraph(x)
>> @@ -1270,6 +1274,16 @@ static inline int sane_iscase(int x, int is_lower)
>> return (x & 0x20) == 0;
>> }
>>
>> +static inline int sane_isblank(int c)
>> +{
>> + return c == ' ' || c == '\t';
>> +}
>> +
>> +static inline int sane_isgraph(int c)
>> +{
>> + return isprint(c) && !isspace(c);
>> +}
next prev parent reply other threads:[~2023-02-27 19:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-26 11:50 [PATCH v2 0/5] Clean up wildmatch.c Masahiro Yamada
2023-02-26 11:50 ` [PATCH v2 1/5] git-compat-util: add isblank() and isgraph() Masahiro Yamada
2023-02-26 18:45 ` René Scharfe
2023-02-27 19:39 ` Junio C Hamano [this message]
2023-02-26 11:50 ` [PATCH v2 2/5] wildmatch: remove IS*() macros Masahiro Yamada
2023-02-26 11:50 ` [PATCH v2 3/5] wildmatch: remove NEGATE_CLASS(2) macros with trivial refactoring Masahiro Yamada
2023-02-26 11:50 ` [PATCH v2 4/5] wildmatch: use char instead of uchar Masahiro Yamada
2023-02-27 20:07 ` Junio C Hamano
2023-02-26 11:50 ` [PATCH v2 5/5] wildmatch: more cleanups after killing uchar Masahiro Yamada
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