Re: [PATCH] use strpbrk(3) to search for characters from a given set

["René Scharfe" <l.s.r@web.de>]

Am 24.02.20 um 18:10 schrieb Junio C Hamano:
> René Scharfe <l.s.r@web.de> writes:
>
>> We can check if certain characters are present in a string by calling
>> strchr(3) on each of them, or we can pass them all to a single
>> strpbrk(3) call.  The latter is shorter, less repetitive and slightly
>> more efficient, so let's do that instead.
>>
>> Signed-off-by: René Scharfe <l.s.r@web.de>
>> ---
>>  builtin/show-branch.c              | 2 +-
>>  compat/mingw.c                     | 2 +-
>>  mailinfo.c                         | 3 +--
>>  t/helper/test-windows-named-pipe.c | 2 +-
>>  4 files changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/builtin/show-branch.c b/builtin/show-branch.c
>> index 35d7f51c23..8c90cbb18f 100644
>> --- a/builtin/show-branch.c
>> +++ b/builtin/show-branch.c
>> @@ -536,7 +536,7 @@ static void append_one_rev(const char *av)
>>  		append_ref(av, &revkey, 0);
>>  		return;
>>  	}
>> -	if (strchr(av, '*') || strchr(av, '?') || strchr(av, '[')) {
>> +	if (strpbrk(av, "*?[")) {
>
>
> The changes in the patch obviously look all correct.
>
> I wonder how we can exploit Coccinelle to do this kind of
> transformations, though.  Would it be possible to say
>
>  * if we see "strchr(S, C1) || strchr(S, C2)", transform it to
>    "strpbrk(S, concat(stringify(C1),stringify(C2)))"; and
>  * if we see "strpbrk(S, N) || strchr(S, C)", transform it to
>    "strpbrk(S, concat(N, stringify(C))";
>
> and let the tool apply these two rules repeatedly, to catch the
> pattern to find any number of needle character in the same haystack?

That would be nice.  I briefly considered it, but I only can think of a
silly way to convert char literals to strings (by using one rule for
each possible character value), I don't know how to concatenate strings
in Coccinelle (simply putting them next to each other as in C doesn't
seem to work), and I don't know how to apply a rule recursively to allow
transforming an arbitrarily long chain of strchr() calls. :-/

René