From: "Drew Adams" <drew.adams@oracle.com>
To: "'Tassilo Horn'" <tassilo@member.fsf.org>, <help-gnu-emacs@gnu.org>
Subject: RE: How do I remove "reference to free variable" warnings onbuffer-local variables?
Date: Mon, 9 Nov 2009 09:40:12 -0800 [thread overview]
Message-ID: <FA092323BF6A499D96F89DFBFB877F44@us.oracle.com> (raw)
In-Reply-To: <87vdhjk5ph.fsf@thinkpad.tsdh.de>
> ,----[ (info "(elisp)Compiler Errors") ]
> | You can tell the compiler that a function is defined using
> | `declare-function' (*note Declaring Functions::). Likewise, you can
> | tell the compiler that a variable is defined using `defvar' with no
> | initial value.
> |
> | You can suppress the compiler warning for a specific use of an
> | undefined variable VARIABLE by conditionalizing its use on
> | a `boundp' test, like this:
> |
> | (if (boundp 'VARIABLE) ...VARIABLE...)
> `----
>
> So in your case you could add something like
> (or (boundp 'some-variable) (defvar some-variable))
> at the top of your file.
I don't think so - but I'm no expert on this.
`(defvar some-variable)' does not assign a value to the variable. It is used
(AFAIK) only to suppress a compiler warning. As such, there is no need and no
reason to put it behind `(boundp 'some-variable)'.
Since it does not assign a value, there is typically also no need to take
special measures for local values vs default value. Just use `(defvar
some-variable)' at the top level of a file, if you want to suppress the compiler
warning generally for that variable.
What that passage from the manual is saying, I think, is that you can use
`boundp' to suppress the warning only locally if you want, "for a specific use
of an undefined variable". In the example you gave, `defvar' doesn't really
constitute a "use" of the variable - or if it does, it is not a use that would
cause a warning.
An example of using `boundp' to suppress a warning would be `(if (boundp 'foo)
foo bar)'. Here, if `foo' is not bound, no warning is issued. If `bar' is
unbound, you will get the warning for `bar', since it is not protected by
`boundp'.
IOW, as an alternative to using `(defvar foo)', which suppresses all warnings
about foo being unbound, you can use `(boundp 'foo)' to suppress the unbound
warning for only a specific use of the variable. This warning suppression via
`boundp' was new with Emacs 22.
Again, I'm no expert on this. Others will no doubt correct me. But I'm pretty
sure that the example you gave is not useful: the `boundp' test is not needed,
and it doesn't do anything, since the "use" of the variable for which the
warning would be suppressed here is simply `(defvar some-variable)', which
doesn't issue a warning anyway.
next prev parent reply other threads:[~2009-11-09 17:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-09 15:10 How do I remove "reference to free variable" warnings on buffer-local variables? rocky
2009-11-09 16:45 ` Tassilo Horn
2009-11-09 17:40 ` Drew Adams [this message]
2009-11-09 18:58 ` How do I remove "reference to free variable" warnings onbuffer-local variables? Tassilo Horn
[not found] ` <mailman.10351.1257785158.2239.help-gnu-emacs@gnu.org>
2009-11-09 17:28 ` How do I remove "reference to free variable" warnings on buffer-local variables? rocky
2009-11-09 17:40 ` Pascal J. Bourguignon
2009-11-11 5:09 ` Stefan Monnier
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