From: Csaba Raduly <rcsaba@gmail.com>
To: Matthew Rickard <rickard.matt@gmail.com>,
cygwin list <cygwin@cygwin.com>
Subject: Re: 3.4.6-1 shm_open always returns -1, errno EINVAL
Date: Sun, 12 Mar 2023 11:35:26 +0100 [thread overview]
Message-ID: <CAEhDDbBcB61X_FxJynpwva8Mm5=UatDDfbEowup7ydO67WwGWg@mail.gmail.com> (raw)
In-Reply-To: <da1d3c87-b83d-c5f2-95e9-d38952da0703@gmail.com>
Hi Matthew,
On Sun, 12 Mar 2023 at 07:44, Matthew Rickard wrote:
>
> Hi all,
>
> Cygwin 3.4.6-1 shm_open seems to reject all calls, returning the value
> -1 and setting errno to 22 EINVAL.
>
> For example, this program:
>
> #include <sys/mman.h>
> #include <fcntl.h>
> #include <errno.h>
> #include <stdio.h>
>
> int main() {
> int res = shm_open("123", O_CREAT | O_RDWR, 0666);
> int error = errno;
> printf("res=%d errno=%d\n", res, errno);
> if (error == EINVAL)
> printf("That's EINVAL\n");
> return 0;
> }
>
> Says:
>
> $ gcc -Og -o tiny tiny.c; ./tiny
> res=-1 errno=22
> That's EINVAL
>
https://man7.org/linux/man-pages/man3/shm_open.3.html says:
For portable use, a shared memory object should be identified by
a name of the form /somename; that is, a null-terminated string
of up to NAME_MAX (i.e., 255) characters consisting of an initial
slash, followed by one or more characters, none of which are
slashes.
Changing the shm_open call to
shm_open("/123", O_CREAT | O_RDWR, 0666);
returns 3 and sets errno to zero.
Csaba
--
You can get very substantial performance improvements
by not doing the right thing. - Scott Meyers, An Effective C++11/14 Sampler
So if you're looking for a completely portable, 100% standards-conformant way
to get the wrong information: this is what you want. - Scott Meyers (C++TDaWYK)
next prev parent reply other threads:[~2023-03-12 10:35 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-12 6:44 Matthew Rickard
2023-03-12 10:35 ` Csaba Raduly [this message]
2023-03-12 22:55 ` Matthew Rickard
2023-03-13 15:07 ` [EXTERNAL] " Lavrentiev, Anton (NIH/NLM/NCBI) [C]
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