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Re: Difficulties from the combination of functions "call" and "eval"

From: Paul Smith
Subject: Re: Difficulties from the combination of functions "call" and "eval"
Date: Sun, 18 Jan 2015 14:51:22 -0500

On Sun, 2015-01-18 at 20:38 +0100, SF Markus Elfring wrote:
> > Try changing eval to info
> This introspection approach will not work in the moment
> when I stumble on the mentioned error messages.

Why will it not work?  $(info ...) is a no-op statement.  It can appear
anywhere and has zero effect on the running of make, except to generate
output to stdout.

But in your case I don't think it will help, because you are
misunderstanding what eval *does*, rather than being not sure about how
it will expand things.

> > and then inspect the output to see if it makes sense as a makefile.
> The result should become components for recipes in my use case.

As described before, this is not right.  $(eval ...) is used to
internalize make syntax.  The result of expanding $(eval ...) is the
_empty string_, so putting it in a recipe results in NOTHING being added
to the recipe.

It is not appropriate for use inside recipes, or for generating parts of
a recipe.

You can use $(call ...) for this, if needed, but not $(eval ...).

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