please document if ENOTSUP == EOPNOTSUPP

  Hello.

Please document the difference between these error codes in the libc
documentation.

I am posting on this list because I have been told to do so at
https://sourceware.org/bugzilla/show_bug.cgi?id=2363

The patch below is also available there as attachment 11383.

Thanks.

Description: Document that EOPNOTSUPP and ENOTSUP are equal, not distinct
Bug-Debian: https://bugs.debian.org/337013
Forwarded: https://sourceware.org/bugzilla/show_bug.cgi?id=2363
Author: Nicolas Boulenguez <nicolas@debian.org>
Author: Florian Weimer <fweimer@redhat.com>
  

On 8/21/19 11:06 AM, Nicolas Boulenguez wrote:
> Hello.
> 
> Please document the difference between these error codes in the libc
> documentation.
> 
> I am posting on this list because I have been told to do so at
> https://sourceware.org/bugzilla/show_bug.cgi?id=2363
> 
> The patch below is also available there as attachment 11383.
> 
> Thanks.
> 
> Description: Document that EOPNOTSUPP and ENOTSUP are equal, not distinct
> Bug-Debian: https://bugs.debian.org/337013
> Forwarded: https://sourceware.org/bugzilla/show_bug.cgi?id=2363
> Author: Nicolas Boulenguez <nicolas@debian.org>
> Author: Florian Weimer <fweimer@redhat.com>

Florian,

Are you part-author of these changes?

This looks OK to me with the suggestions accepted.

Please post a v2.

> 
> --- a/manual/errno.texi
> +++ b/manual/errno.texi
> @@ -84,11 +84,18 @@
>  reserved names.  @xref{Reserved Names}.
>  
>  The error code values are all positive integers and are all distinct,
> -with one exception: @code{EWOULDBLOCK} and @code{EAGAIN} are the same.
> -Since the values are distinct, you can use them as labels in a
> -@code{switch} statement; just don't use both @code{EWOULDBLOCK} and
> -@code{EAGAIN}.  Your program should not make any other assumptions about
> +so they can be used as labels in a @code{switch} statement.
> +Your program should not make any other assumptions about
>  the specific values of these symbolic constants.
> +Moreover, @theglibc{} does two exceptions:

Suggest:
There are two exceptions to this rule:

> +@itemize @bullet
> +@item The values of @code{AGAIN} and @code{EWOULDBLOCK} are the

s/AGAIN/EAGAIN/g

s/the same/equal/g

> +same on every supported operating system.
> +@item The values of @code{ENOTSUP} and @code{EOPNOTSUPP} are equal
> +on some supported operating systems, for example GNU/Linux.
> +@end itemize
> +To make your program portable, you should check for both codes and
> +treat them the same.

OK.

>  
>  The value of @code{errno} doesn't necessarily have to correspond to any
>  of these macros, since some library functions might return other error
> @@ -383,8 +390,7 @@
>  @standards{POSIX.1, errno.h}
>  @errno{EAGAIN, 35, Resource temporarily unavailable}
>  The call might work if you try again
> -later.  The macro @code{EWOULDBLOCK} is another name for @code{EAGAIN};
> -they are always the same in @theglibc{}.
> +later.

OK.

>  
>  This error can happen in a few different situations:
>  
> @@ -395,12 +401,6 @@
>  until some external condition makes it possible to read, write, or
>  connect (whatever the operation).  You can use @code{select} to find out
>  when the operation will be possible; @pxref{Waiting for I/O}.
> -
> -@strong{Portability Note:} In many older Unix systems, this condition
> -was indicated by @code{EWOULDBLOCK}, which was a distinct error code
> -different from @code{EAGAIN}.  To make your program portable, you should
> -check for both codes and treat them the same.

OK.

> -
>  @item
>  A temporary resource shortage made an operation impossible.  @code{fork}
>  can return this error.  It indicates that the shortage is expected to
> @@ -411,16 +411,16 @@
>  so usually an interactive program should report the error to the user
>  and return to its command loop.
>  @end itemize
> +
> +@strong{Portability Note:} In @theglibc{},
> +@code{EAGAIN} and @code{EWOULDBLOCK} are equal.
> +Portable code should check for both errors and treat them the same.

OK.

>  @end deftypevr
>  
>  @deftypevr Macro int EWOULDBLOCK
>  @standards{BSD, errno.h}
>  @errno{EWOULDBLOCK, EAGAIN, Operation would block}
>  In @theglibc{}, this is another name for @code{EAGAIN} (above).
> -The values are always the same, on every operating system.
> -
> -C libraries in many older Unix systems have @code{EWOULDBLOCK} as a
> -separate error code.

OK.

>  @end deftypevr
>  
>  @deftypevr Macro int EINPROGRESS
> @@ -492,6 +492,10 @@
>  error can happen for many calls when the object does not support the
>  particular operation; it is a generic indication that the server knows
>  nothing to do for that call.
> +
> +@strong{Portability Note:} Depending on the operating system, the
> +@code{EOPNOTSUPP} and @code{ENOTSUP} macros may have the same value.
> +Portable code should check for both errors and treat them the same.

OK.

>  @end deftypevr
>  
>  @deftypevr Macro int EPFNOSUPPORT
> @@ -764,6 +768,10 @@
>  
>  If the entire function is not available at all in the implementation,
>  it returns @code{ENOSYS} instead.
> +
> +@strong{Portability Note:} Depending on the operating system, the
> +@code{EOPNOTSUPP} and @code{ENOTSUP} macros may have the same value.
> +Portable code should check for both errors and treat them the same.

OK.

>  @end deftypevr
>  
>  @deftypevr Macro int EILSEQ
>
  

* Carlos O'Donell:

> Are you part-author of these changes?

I don't think so, I just made a comment in passing.

Thanks,
Florian