From: Ken Brown <kbrown@cornell.edu>
To: cygwin-patches@cygwin.com
Subject: Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX
Date: Thu, 28 Jan 2021 17:28:54 -0500 [thread overview]
Message-ID: <a4cd3c3f-d217-026a-3cce-b29187ecd1e9@cornell.edu> (raw)
In-Reply-To: <20210128161304.GC4393@calimero.vinschen.de>
On 1/28/2021 11:13 AM, Corinna Vinschen via Cygwin-patches wrote:
> On Jan 28 17:07, Corinna Vinschen via Cygwin-patches wrote:
>> On Jan 28 08:42, Ken Brown via Cygwin-patches wrote:
>>> On 1/28/2021 5:20 AM, Corinna Vinschen via Cygwin-patches wrote:
>>>> On Jan 27 21:51, Ken Brown via Cygwin-patches wrote:
>>>>> According to the Linux man page for getdtablesize(3), the latter is
>>>>> supposed to return "the maximum number of files a process can have
>>>>> open, one more than the largest possible value for a file descriptor."
>>>>> The constant OPEN_MAX_MAX is the only limit enforced by Cygwin, so we
>>>>> now return that.
>>>>>
>>>>> Previously getdtablesize returned the current size of cygheap->fdtab,
>>>>> Cygwin's internal file descriptor table. But this is a dynamically
>>>>> growing table, and its current size does not reflect an actual limit
>>>>> on the number of open files.
>>>>>
>>>>> With this change, gnulib now reports that getdtablesize and
>>>>> fcntl(F_DUPFD) work on Cygwin. Packages like GNU tar that use the
>>>>> corresponding gnulib modules will no longer use gnulib replacements on
>>>>> Cygwin.
>>>>> ---
>>>>> winsup/cygwin/syscalls.cc | 2 +-
>>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc
>>>>> index 5da05b18a..1f16d54b9 100644
>>>>> --- a/winsup/cygwin/syscalls.cc
>>>>> +++ b/winsup/cygwin/syscalls.cc
>>>>> @@ -2887,7 +2887,7 @@ setdtablesize (int size)
>>>>> extern "C" int
>>>>> getdtablesize ()
>>>>> {
>>>>> - return cygheap->fdtab.size;
>>>>> + return OPEN_MAX_MAX;
>>>>> }
>>>>
>>>> getdtablesize is used internally, too. After this change, the values
>>>> returned by sysconf and getrlimit should be revisited as well.
>>>
>>> They will now return OPEN_MAX_MAX, as I think they should. The only
>>> question in my mind is whether to simplify the code by removing the calls to
>>> getdtablesize, something like this (untested):
>>
>> But then again, what happens with OPEN_MAX in limits.h? Linux removed
>> it entirely. Given we have such a limit and it's not flexible as on
>> Linux, should we go ahead, drop OPEN_MAX_MAX entirely and define
>> OPEN_MAX as 3200?
>
> ...ideally by adding a file include/cygwin/limits.h included by
> include/limits.h, which defines __OPEN_MAX et al, as required.
I'm not completely sure I follow. Do you mean include/cygwin/limits.h should
contain
#define __OPEN_MAX 3200
and include/limits.h should contain
#define OPEN_MAX __OPEN_MAX ?
For the sake of my education, could you explain the reason for this?
Thanks.
Ken
next prev parent reply other threads:[~2021-01-28 22:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-28 2:51 Ken Brown
2021-01-28 10:20 ` Corinna Vinschen
2021-01-28 13:42 ` Ken Brown
2021-01-28 16:07 ` Corinna Vinschen
2021-01-28 16:13 ` Corinna Vinschen
2021-01-28 22:28 ` Ken Brown [this message]
2021-01-29 19:23 ` Ken Brown
2021-02-01 9:42 ` Corinna Vinschen
2021-01-28 20:33 ` Ken Brown
2021-02-01 9:50 ` Corinna Vinschen
2021-02-01 10:46 ` Corinna Vinschen
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