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Re: Science to suppress compiler warnings

From: Davis Herring
Subject: Re: Science to suppress compiler warnings
Date: Tue, 2 Jun 2009 16:36:22 -0700 (PDT)
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> Elisp manual at "Compiler Errors" section (16.6) says we should
> conditionalize variable use with a boundp test (same thing for
> undefined function) but I find it very unpractical.
> I thought (probably was wrong) that:
> (eval-when-compile (defvar foo nil))
> would do the trick. Is it the correct way to avoid warnings ?

That should work if you have confidence that it will be defined (and
non-void) at runtime.  The [f]boundp, of course, will let you react to it
not existing then, if there's a real possibility (as with an old Emacs
version) of it not being there.

> Also while at it, here is what I got when compiling an old
> package:
> records.el:931:49:Warning: reference to free variable
> `records-link-menu-map'
> In records-mode:
> records.el:1066:23:Warning: assignment to free variable
>     `records-link-menu-map'
> What is the difference between these two warnings exactly ?
> Adding a defvar at the right place fixed that but to feed my
> curiosity.

The first is for reading, the second for writing; that's all.


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