Re: [PATCH] Cygwin: pty: Add workaround for ISO-2022 and ISCII in convert_mb_str().

[Thomas Wolff <towo@towo.net>]

Am 11.09.2020 um 16:06 schrieb Corinna Vinschen:
> On Sep 11 21:35, Takashi Yano via Cygwin-patches wrote:
>> Hi Corinna,
>>
>> On Fri, 11 Sep 2020 14:08:40 +0200
>> Corinna Vinschen wrote:
>>> On Sep 11 19:54, Takashi Yano via Cygwin-patches wrote:
>>>> - In convert_mb_str(), exclude ISO-2022 and ISCII from the processing
>>>>    for the case that the multibyte char is splitted in the middle.
>>>>    The reason is as follows.
>>>>    * ISO-2022 is too complicated to handle correctly.
>>>>    * Not sure what to do with ISCII.
>>>> ---
>>>>   winsup/cygwin/fhandler_tty.cc | 9 +++++++--
>>>>   1 file changed, 7 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
>>>> index 37d033bbe..ee5c6a90a 100644
>>>> --- a/winsup/cygwin/fhandler_tty.cc
>>>> +++ b/winsup/cygwin/fhandler_tty.cc
>>>> @@ -117,6 +117,9 @@ CreateProcessW_Hooked
>>>>     return CreateProcessW_Orig (n, c, pa, ta, inh, f, e, d, si, pi);
>>>>   }
>>>>   
>>>> +#define IS_ISO_2022(x) ( (x) >= 50220 && (x) <= 50229 )
>>>> +#define IS_ISCII(x) ( (x) >= 57002 && (x) <= 57011 )
>>>> +
>>>>   static void
>>>>   convert_mb_str (UINT cp_to, char *ptr_to, size_t *len_to,
>>>>   		UINT cp_from, const char *ptr_from, size_t len_from,
>>>> @@ -126,8 +129,10 @@ convert_mb_str (UINT cp_to, char *ptr_to, size_t *len_to,
>>>>     tmp_pathbuf tp;
>>>>     wchar_t *wbuf = tp.w_get ();
>>>>     int wlen = 0;
>>>> -  if (cp_from == CP_UTF7)
>>>> -    /* MB_ERR_INVALID_CHARS does not work properly for UTF-7.
>>>> +  if (cp_from == CP_UTF7 || IS_ISO_2022 (cp_from) || IS_ISCII (cp_from))
>>>> +    /* - MB_ERR_INVALID_CHARS does not work properly for UTF-7.
>>>> +       - ISO-2022 is too complicated to handle correctly.
>>>> +       - FIXME: Not sure what to do for ISCII.
>>>>          Therefore, just convert string without checking */
>>>>       wlen = MultiByteToWideChar (cp_from, 0, ptr_from, len_from,
>>>>   				wbuf, NT_MAX_PATH);
>>>> -- 
>>>> 2.28.0
>>> I'd prefer to not handle them at all.  We just don't support these
>>> charsets, same as JIS, EBCDIC, you name it, which are not ASCII
>>> compatible.  Let's please just drop any handling for these weird
>>> or outdated codepages.
>> What do you mean by "just drop any handling"?
>>
>> Do you mean remove following if block?
>>>> +  if (cp_from == CP_UTF7 || IS_ISO_2022 (cp_from) || IS_ISCII (cp_from))
>>>> +    /* - MB_ERR_INVALID_CHARS does not work properly for UTF-7.
>>>> +       - ISO-2022 is too complicated to handle correctly.
>>>> +       - FIXME: Not sure what to do for ISCII.
>>>>          Therefore, just convert string without checking */
>>>>       wlen = MultiByteToWideChar (cp_from, 0, ptr_from, len_from,
>>>>   				wbuf, NT_MAX_PATH);
>> In this case, the conversion for ISO-2022, ISCII and UTF-7 will
>> not be done correctly.
>>
>> Or skip charset conversion if the codepage is EBCDIC, ISO-2022
>> or ISCII? What should we do for UTF-7?
> Nothing, just like for any other of these weird charsets.  Cygwin never
> supported any charset which wasn't at least ASCII compatible in the
> 0 <= x <= 127 range.
Actually, in Shift-JIS (CP932, supported via locale ja_JP.sjis), 0x5C is 
¥ :/
>    Just ignore them and the possibility that a
> user chooses them for fun.
>
>> What should happen if user or apps chage codepage to one of them?
> Garbage output, I guess.  We shouldn't really care.
>
>
> Corinna