From: Jason Green <mail AT jgreen4 DOT fsnet DOT co DOT uk>
To: Laurynas Biveinis <lauras AT softhome DOT net>
Cc: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>, djgpp-workers AT delorie DOT com
Subject: Re: Symify fixes
Date: Thu, 31 Aug 2000 19:12:57 +0100
Message-ID: <4k7tqskuugpt8r78ls4hnt2cfhuggjdtu3@4ax.com>
References: <226lqssqgqp6i9nk82rvrqhl9aaia029e9 AT 4ax DOT com> <7458-Mon28Aug2000203504+0300-eliz AT is DOT elta DOT co DOT il> <ltflqs8ouggncaukmesirq7rsbsi4umrj5 AT 4ax DOT com> <8011-Mon28Aug2000234727+0300-eliz AT is DOT elta DOT co DOT il> <ttvnqs0p0rib0eja7eiijst64vbgp9tl1b AT 4ax DOT com> <39AD1BF3 DOT 139CB5DB AT softhome DOT net> <9003-Wed30Aug2000195653+0300-eliz AT is DOT elta DOT co DOT il> <3b5rqskv9adg5lcc3p4nhg2doib859r3n8 AT 4ax DOT com> <39AE0E92 DOT C8E0A73B AT softhome DOT net>
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Reply-To: djgpp-workers AT delorie DOT com

On Thu, 31 Aug 2000 09:51:46 +0200, you wrote:

> > 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.
> 
> And if I have not missing anything, this is the only way bail() will be 
> used - right after failed syscall.

bail() will be called due to fseek outside file boundary, or fread
past eof; these are not failed system calls.  If you know these
functions will always set errno=0 (no POSIX function is required to do
that) then your code would be safe.  

In that case, the only change I would make would be to rename it
bail_syserr(), or something like that, to be clearer about its
purpose, and to add some comment warning that it probably won't work
outside of djgpp.

> If you don't change your mind about errno, then I'll commit current bail()
> version. It's code of yours, after all.

Sure it's my code.  I have no problem, though, if you want to improve
it with inside knowledge of how djgpp implements errno.  Perhaps you
could mail the patch first, I'll re-run the tests I did, then you can
commit it.

> > There is some generic
> > code by Richard Stevens which takes printf style arguments to provide
> > better context to the error reporting, I can dig this out if you like.
> 
> Yes, I'm curious.

There are 5 functions for putting error messages to stderr:

err_ret():  Nonfatal error related to a system call. 
            Print a message and return. 

err_sys():  Fatal error related to a system call. 
            Print a message and terminate.

err_dump(): Fatal error related to a system call. 
            Print a message, dump core, and terminate.

err_msg():  Nonfatal error unrelated to a system call. 
            Print a message and return. 

err_quit(): Fatal error unrelated to a system call. 
            Print a message and terminate.

The code is in apue/advio/ourhdr.h and apue/lib.44/error.c, from the
archive http://www.kohala.com/start/apue.tar.Z

No changes are required to compile with DJGPP, 
just #include "ourhdr.h" and link with error.c.
-- 
[please cc all replies, thanks]