From: Michal Nowak <mnowak@startmail.com>
Date: Fri, 01 Feb 2019 19:00:37 GMT
Subject: Re: Broken interactive rebase text after some UTF-8 characters
Message-ID: <7fe4edcd-f4ec-3ad5-a9ea-e4015e4afc37@startmail.com>
In-Reply-To: <xmqqpnsbzaa6.fsf@gitster-ct.c.googlers.com>

On 02/01/19 06:30 PM, Junio C Hamano wrote:
> Michal Nowak <mnowak@startmail.com> writes:
> 
>>> You already have that example. Just take the UTF-8 text in your original
>>> bug report, put it into something like
>>>
>>> 	int main(int argc, char **argv)
>>> 	{
>>> 		char utf8[] = "... your text here...";
>>>
>>> 		printf("%.*s", (int)(sizeof(utf8) - 1), utf8);
>>>
>>> 		return 0;
>>> 	}
> 
> When replayed literally, this is not a very good test.
> 
>> {global} newman@lenovo:~ $ cat printf.c
>> #include <stdio.h>
>> //#include <gettext.h>
>> int main(int argc, char **argv) {
>>    char utf8[] = "Gergő Mihály Doma\n";
>>    printf("%.*s", (int)(sizeof(utf8) - 1), utf8);
>>    return 0;
>> }
> 
> And this is replaying it literally.
> 
> The current working suspicion in this thread is that the platform
> printf("%.*s", num, str) emits up to num "characters" starting at
> str, which is an incorrect implementation, as it should emit up to
> num "bytes".
> 
> Notice that the num in this case is the byte count of that utf8[]
> string.  That number is always larger than the number of "characters"
> for a string with multi-byte character(s) in it.  Let's say that the
> sample string has N "characters", and it is N+X "bytes" long, where
> X > 1.
> 
> If the suspicion is correct, i.e. the way the printf implementation
> is broken on this platform is that it shows up to num "characters",
> then the call is asking to show up to N+X "characters".  The buggy
> printf shows all the available N "characters", notices the string
> stops there, and finishes.  So you won't _see_ the bug with that
> test program.
> 
> Instead, use something like this.
> 
>          #include <stdio.h>
> 
>          int main(int ac, char **av)
>          {
>                  char utf8[] = "ふabc";
>                  printf("%.*s\n", 4, utf8);
>                  return 0;
>          }
> 
> With or without gettext or i18n, the output must end with 'a' followed
> by a newline, and you must not see 'b' nor 'c'.  Otherwise your printf
> is broken.
> 

The output ends with 'a' for me on OpenIndiana:

{global} newman@lenovo:~ $ gcc tp.c -o tp && ./tp
ふa

Though, I can reproduce the problem with Alban's test case the exact 
same way he wrote earlier today.

Michal