Dept of Utterly Useless Error Messages

[Frank Cox]

On Sun, 29 Apr 2007 23:54:06 +0100
Timothy Murphy <tim at birdsnest.maths.tcd.ie> wrote:

> When I run xpdf I get the message
> "Warning: Attempt to remove nonexistent passive grab".
> 
> The program seems to run in spite of this.
> I googled for the message, with a number of hits,
> but none had any suggestion of a solution, or a cause.

Really?

This is  on the first page of Google when I search for that phrase:

http://www.cs.bham.ac.uk/research/projects/poplog/bugfixes/BUGREPORTS

On that page, you find this explanation:

QUOTE:
Warning: Attempt to remove non-existent passive grab

    Answer: They are meaningless, and you want to ignore them.  Do this
    (from Kee Hinckley) by installing an XtWarning handler that
    explicitly looks for them and discards them:

    static void xtWarnCB(String message) { if (asi_strstr(message,
    "non-existant passive grab", TRUE)) return; ...

    They come from Xt, and (W. Scott Meeks): "it's something that the
    designers of Xt decided the toolkit should do. Unfortunately, Motif
    winds up putting passive grabs all over the place for the menu
    system.  On the one hand, we want to remove all these grabs when
    menus get destroyed so that they don't leak memory; on the other
    hand, it's almost impossible to keep track of all the grabs, so we
    have a conservative strategy of ungrabbing any place where a grab
    could have been made and we don't explicitly know that there is no
    grab. The unfortunate side effect is the little passive grab warning
    messages. We're trying to clean these up where possible, but there
    are some new places where the warning is generated.  Until we get
    this completely cleaned up (1.2 maybe), your best bet is probably to
    use a warning handler."
END OF QUOTE

It appears to be a cosmetic bug.

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