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Re: compiler macros without byte-compilation

From: Stefan Monnier
Subject: Re: compiler macros without byte-compilation
Date: Fri, 20 Mar 2015 09:42:06 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux)

>  => ((lambda nil (message "Done !")) "compiler-macro")
> Now I'm puzzled : why does this happen ? foobar wasn't compiled here !

The exact cases where compiler-macros are used are unspecified and
likely to change between versions.

If you want to know the details: compiler-macros are expanded by
macroexpand-all.  So everytime we rely on macroexpand-all (i.e. "eager"
expansion) rather than on macroexpand (i.e. "lazy" expansion), compiler
macros will be expanded.

"Lazy" macroexpansion is on the way out: `eval' does not call
macroexpand-all (because it can happen that `eval' is called repeatedly
in a tight loop to evaluate very short code sequences, where going
through macroexpand-all might be detrimental for performance), but
pretty much all other paths to `eval' do or should (i.e. `load',
`eval-region', ...).


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