[PATCH] Cygwin: console: Fix segfault on shared_console_info access.

[Brian Inglis]

On 2020-02-24 11:33, Corinna Vinschen wrote:
> On Feb 25 01:10, Takashi Yano wrote:
>> On Mon, 24 Feb 2020 11:08:35 +0100
>> Corinna Vinschen wrote:
>> [...]
>>> Btw., are you testing the console with black background?  I'm asking
>>> because I'm using the console with grey background and black characters,
>>> and I'm always seeing artifacts when using vim in xterm mode.
>>>
>>> E.g., open vim on the fork-setsid.c source in the console in xterm
>>> mode.  Move the cursor to the beginning of the word `setsid'.  Now
>>> press the three chars
>>>
>>>   c h <CR>
>>>
>>> this moves the setsid call to the next line.  But it also adds
>>> black background after `setsid();'.  Simiar further actions always
>>> create black background artifacts.
>>>
>>> Is there anything we can do against that?
>>
>> This seems to be a bug of windows console. It also occurs in wsl.
>> /bin/echo -e '\033[H\033[5L'
>> causes the similar result.
> 
> Oh well.
> 
>> The following code cause the problem as well.
>>
>> #include <windows.h>
>> int main()
>> {
>>     CONSOLE_SCREEN_BUFFER_INFO sbi;
>>     SMALL_RECT r;
>>     COORD c = {0, 0};
>>     CHAR_INFO f = {' ', 0};
>>     HANDLE h = GetStdHandle(STD_OUTPUT_HANDLE);
>>     DWORD n;
>>     ReadConsoleOutputAttribute(h, &f.Attributes, 1, c, &n);
>>     GetConsoleScreenBufferInfo(h, &sbi);
>>     c.X = 0;
>>     c.Y = sbi.srWindow.Top + 5;
>>     ScrollConsoleScreenBuffer(h, &sbi.srWindow, NULL, c, &f);
>>     return 0;
>> }
> 
> Is there some kind of workaround for that problem?  Otherwise defaulting
> to a (broken) xterm mode instead of a (working) cygwin mode is a bit
> questionable, isn't it?

I'm a windows with white backgrounds user and e.g. vim in latest Cygwin under
cmd requires typing ctrl-L to refresh the screen every couple of commands or
motions; looks okay under mintty in windows with white backgrounds.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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