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* Using the content of a dynamic variable in a macro
@ 2023-02-24  6:31 Damien Cassou
  2023-02-26 11:47 ` Michael Heerdegen
  0 siblings, 1 reply; 2+ messages in thread
From: Damien Cassou @ 2023-02-24  6:31 UTC (permalink / raw)
  To: help-gnu-emacs

Hi,

I'm wondering why the code below works but won't compile.

foo.el:
  (defvar foo-var '((message "hello world")))
  
  (defmacro foo-macro ()
    `(progn
       ,@foo-var))
  
  (defun foo-fun ()
    (foo-macro))


$ emacs --batch -l foo.el --eval '(foo-fun)'
hello world

$ emacs --batch --eval '(find-file "foo.el")' --eval '(emacs-lisp-byte-compile)'
In toplevel form:
foo.el:32:1: Error: Symbol’s value as variable is void: foo-var

Why isn't the compiler aware of the foo-var variable?

-- 
Damien Cassou

"Success is the ability to go from one failure to another without
losing enthusiasm." --Winston Churchill



^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: Using the content of a dynamic variable in a macro
  2023-02-24  6:31 Using the content of a dynamic variable in a macro Damien Cassou
@ 2023-02-26 11:47 ` Michael Heerdegen
  0 siblings, 0 replies; 2+ messages in thread
From: Michael Heerdegen @ 2023-02-26 11:47 UTC (permalink / raw)
  To: Damien Cassou; +Cc: help-gnu-emacs

Damien Cassou <damien@cassou.me> writes:

> I'm wondering why the code below works but won't compile.
>
> foo.el:
>   (defvar foo-var '((message "hello world")))
>   
>   (defmacro foo-macro ()
>     `(progn
>        ,@foo-var))
>   
>   (defun foo-fun ()
>     (foo-macro))
> [...]
> foo.el:32:1: Error: Symbol’s value as variable is void: foo-var
>
> Why isn't the compiler aware of the foo-var variable?

The compiler is aware of it, but it doesn't eval the definition.  It is
a feature that the compiler normally does not load any part of the
program when compiling, including variable definitions.  Note that in
the general case, evaluating a defvar form might require to load more
parts of a file, or even the complete file.

If you do need to eval something when compiling, use `eval-when-compile'
or `eval-and-compile' respectively.


Michael.



^ permalink raw reply	[flat|nested] 2+ messages in thread

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