From: Brian Candler <B.Candler@...>
Date: 2003-08-02T21:17:15+09:00
Subject: Re: 1.8.0-previewX  rb_sys_fail() on socket instead of an Exception.

On Sat, Aug 02, 2003 at 08:53:03PM +0900, ts wrote:
>  The problem is that appendline() use ferror() when rb_sys_fail() use
>  errno. On linux I have
> 
>    These  functions  should  not fail and do not set the external variable
>                                           ^^^^^^^^^^
>    errno.  (However, in case fileno detects that its  argument  is  not  a
>    valid stream, it must return -1 and set errno to EBADF.)

Interesting. The FreeBSD manpage for ferror says exactly the same, although
omits the sentence in brackets.

However, 'man getc' says:

RETURN VALUES
     If successful, these routines return the next requested object from the
     stream.  Character values are returned as an unsigned char converted to
     an int.  If the stream is at end-of-file or a read error occurs, the rou-
     tines return EOF.  The routines feof(3) and ferror(3) must be used to
     distinguish between end-of-file and error.  If an error occurs, the
                                                 ^^^^^^^^^^^^^^^^^^^^^^^
     global variable errno is set to indicate the error.  The end-of-file con-
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     dition is remembered, even on a terminal, and all subsequent attempts to
     read will return EOF until the condition is cleared with clearerr(3).

Does this mean that Linux's ferror is actually *clearing* errno? Or there is
some circumstance where ferror() returns true but errno is unset?

Regards,

Brian.