Path: utzoo!attcan!telly!lethe!torsqnt!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!brunix!ivan.uucp!jhc
From: jhc@ivan.uucp (James H. Coombs)
Newsgroups: comp.windows.x
Subject: XtAddInput returns; error checking in general
Message-ID: <64840@brunix.UUCP>
Date: 13 Feb 91 16:14:42 GMT
Sender: news@brunix.UUCP
Reply-To: jhc@ivan.uucp (James H. Coombs)
Organization: IRIS - Brown University
Lines: 23

In the man page for XtAddInput()/XtAppAddInput(), I don't see any error
condition to check for.  The call returns an XtInputId, and I suppose
that I am to treat that as opaque information.  Is that right?  I
checked the source code, but I would like some verification on this.

In the source (for X11R4), I found that XtAppErrorMsg() is called if
the condition mask is invalid.  That seems fair enough.

But, I see a subsequent call to XtNew(), which calls malloc().
XtAddInput() then uses the result without checking for a valid
pointer.  It is this pointer that is returned as the XtInputId.
Putting aside the fact that the current implementation of XtAddInput()
will crash if the allocation fails, should I check for a NULL return?
or should this truly be considered opaque?

Is this an issue specific to XtAddInput()? or is there just a
programming lapse in that routine? or is it a lapse in the
documentation?  In other words, should I just assume that all
undocumented errors will be fatal?  It seems inappropriate to check the
source code and then check for returns based upon the current
implementation.

Thanks.  --Jim