[PATCH v8] Cygwin: pipe: Switch pipe mode to blocking mode by default

[Takashi Yano]

Hi Corinna,

On Mon, 28 Oct 2024 12:57:05 +0100
Corinna Vinschen wrote:
> On Oct 28 20:25, Takashi Yano wrote:
> > Is the test case I used different from yours? Without the 2nd arg,
> > $ ./a.exe 40000
> > pipe capacity: 65536
> > write: writable 1, 40000 25536
> > write: writable 1, SIGALRM 24576 960
> > write: writable 0, SIGALRM -1 / Interrupted system call
> 
> This is the same testcase I pasted last week:
> 
>   $ ./x 40000
>   pipe capacity: 65536
>   write: writable 1, 40000 25536
>   write: writable 1, SIGALRM 24576 960
>   write: writable 0, SIGALRM 512 448
>   write: writable 0, SIGALRM 256 192
>   write: writable 0, SIGALRM 128 64
>   write: writable 0, SIGALRM 64 0
>   write: writable 0, SIGALRM -1 / Interrupted system call
> 
> So why does it not get into the last else case after calling
> pipe_data_available()?  Do you get a different return value
> from pipe_data_available()? If so, what and why?

I checked the behaviour in my environment.
__builtin_clzl(960) returns 54 in my environment.
So, result of
	len1 = 1 << (31 - __builtin_clzl (avail));
is undefined. If I modify this to:
	len1 = 1 << (63 - __builtin_clzl (avail));
I can get:

$ ./a.exe 40000 1
pipe capacity: 65536
write: writable 1, 40000 25536
write: writable 1, 24576 960
write: writable 0, 512 448
write: writable 0, 256 192
write: writable 0, 128 64
write: writable 0, 64 0
write: writable 0, -1 / Resource temporarily unavailable

with the commit 686e46ce7148 as well as with my v9 patch.

Could you please fix?

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>