From: Andrey Repin <anrdaemon@yandex.ru>
To: "Lavrentiev, Anton (NIH/NLM/NCBI) [C]" <lavr@ncbi.nlm.nih.gov>,
cygwin@cygwin.com
Subject: Re: Typo in <sys/select.h>?
Date: Tue, 5 Jul 2022 17:55:19 +0300 [thread overview]
Message-ID: <1147442891.20220705175519@yandex.ru> (raw)
In-Reply-To: <DM8PR09MB70954B30D740E778EB65BA41A5819@DM8PR09MB7095.namprd09.prod.outlook.com>
Greetings, Lavrentiev, Anton (NIH/NLM/NCBI) [C]!
> There's some inconsistency between <sys/select.h> and <sys/param.h>:
> sys/select.h has this:
> -----------------------
> /*
> * Select uses bit masks of file descriptors in longs.
> * These macros manipulate such bit fields (the filesystem macros use chars).
> * FD_SETSIZE may be defined by the user, but the default here
> * should be >= NOFILE (param.h).
> */
> #ifndef FD_SETSIZE
> #define FD_SETSIZE 64
> #endif
> ----------------------
> Now, this is the relevant part of sys/param.h looks like this:
> ----------------------
> /* Max number of open files. The Posix version is OPEN_MAX. */
> /* Number of fds is virtually unlimited in cygwin, but we must provide
> some reasonable value for Posix conformance */
> #define NOFILE 8192
> ----------------------
> So it's either "<= NOFILE" that was actually meant to be there in the comment (or,
> an equivalent "should NOT be > NOFILE"), or FD_SETSIZE should have been defined as 8192,
> if the comment is actually correct. Or maybe I'm missing something here :-)
> I understand that if I redefined FD_SETSIZE in my code before including <sys/select.h>,
> it'd work with whatever large (or small) fd_set I need, but that's not what I'm after.
I'm no expert, but it seems the FD_SETSIZE should have been 128.
Long is 8 bytes, 64 bits. One bit if one open file, 64 * 64 = 4096.
--
With best regards,
Andrey Repin
Tuesday, July 5, 2022 17:52:26
Sorry for my terrible english...
next prev parent reply other threads:[~2022-07-05 15:05 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-05 14:13 Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2022-07-05 14:55 ` Andrey Repin [this message]
2022-07-05 21:51 ` Ken Brown
2022-07-06 7:42 ` Corinna Vinschen
2022-07-06 14:01 ` Jon Turney
2022-07-06 14:15 ` Corinna Vinschen
2022-07-06 14:22 ` Corinna Vinschen
2022-07-05 15:11 Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2022-07-06 13:19 Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2022-07-06 14:17 ` Corinna Vinschen
2022-07-06 14:17 Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2022-07-06 14:26 Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2022-07-06 15:07 ` Corinna Vinschen
2022-07-06 15:57 Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2022-07-06 17:03 ` Ken Brown
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