Re: macroexpand and bytecomp.el

[Stefan Monnier]

> (defmacro byte-extrude-byte-code-vectors ()
>   (prog1 (list 'setq 'byte-code-vector
>                (get 'byte-code-vector 'tmp-compile-time-value)
>                'byte-stack+-info
>                (get 'byte-stack+-info 'tmp-compile-time-value))
>     (put 'byte-code-vector 'tmp-compile-time-value nil)
>     (put 'byte-stack+-info 'tmp-compile-time-value nil)))
[...]
> (defvar tmp-var [1 2 3])
> (defvar my-var nil)
> (defmacro my-extrude ()
>  (prog1 (list 'setq 'my-var 'tmp-var)
>  (setq tmp-var nil)))
> (my-extrude)

I don't fully understand your question, but notice that in your macro
you use 'tmp-var in the `setq`, i.e. your macro returns code that uses
the name of the variable and not its content (so the variable will be
read *after* when the code is run rather than when it's macro-expanded),
whereas in `byte-extrude-byte-code-vectors` the macro executes
(get 'byte-code-vector 'tmp-compile-time-value) during the macro
expansion and thus returns code which contains the value therein.

IOW, `byte-extrude-byte-code-vectors` is more akin to:

    (defmacro my-extrude ()
      (prog1 (list 'setq 'my-var tmp-var)
        (setq tmp-var nil)))


- Stefan