Date: Wed, 26 May 1999 09:56:06 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender: eliz AT is
To: Dlanor Blytkerchan <dlanor AT dds DOT nl>
cc: djgpp AT delorie DOT com
Subject: Re: srand() or time()
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On Mon, 24 May 1999, Dlanor Blytkerchan wrote:

> When stepping through this in RHIDE, watching errno like a hawk, immediatly
> after srand(time(0)); errno is set to 22 (ENOENT)

That's because `time' looks for the timezone files on your system, to
correctly handle the DST (Daylight Saving Time) rules.  I guess you
didn't install djtzn202.zip, right?  (See section 22.19 of the FAQ for
more details.)

I believe there's nothing wrong in this behavior of `time'.  The ANSI
C standard says this:

   ... The value of `errno' may be set to nonzero by a library
   function call whether or not there is an error, provided the use of
   `errno' is not documented in the description of the function in
   [the ANSI C Standard].

Since the description of `time' in the ANSI C Standard doesn't include
any references to `errno', `time' is free to assign non-zero values to
`errno'.

> (and thus causes my
> program to believe there's an error, which it wisely ignores).

I think this is a bug in your program.  Programs should only examine
`errno' if they have other, independent means to indicate that the
last function call failed.  In the case of `time', it will return -1
if it fails; *then* you could use `errno' value to find out why it
failed.