Date: Thu, 31 Aug 2000 07:47:13 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
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To: Jason Green <mail AT jgreen4 DOT fsnet DOT co DOT uk>
cc: lauras AT softhome DOT net, djgpp-workers AT delorie DOT com
Subject: Re: Symify fixes
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On Thu, 31 Aug 2000, Jason Green wrote:

> I did actually think about this.  fseek() and fread() are not listed
> (in the POSIX P.G.) as setting errno.

The DJGPP library always sets errno each time a system call (i.e., a
function of Int 21h via __dpmi_int) is made.

> To know that these functions
> will set errno requires inside knowledge of libc, so I played it safe.
> 
> > > if errno != 0?
> 
> It's not sufficient to simply test errno to see if an error occured,
> because it only has meaningful value if tested after a system call
> that has returned some failure indication.

The portable way to check for errno is to set it to zero before the
call to a function, then see if it is still zero after the function
returns.

> > But I agree that a more specific error message is a good idea.
> 
> I don't see how it is possible to give more specific error messages,

I meant to say that adding strerror will result in more specific error
messages.  Saying "read error: Bad file descriptor" is more
informative than just "read error", IMHO.