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Re: [Bug report] Make doesn't know $@ when referenced in the prerequisit

From: Paul Smith
Subject: Re: [Bug report] Make doesn't know $@ when referenced in the prerequisites
Date: Sat, 18 Mar 2017 22:18:43 -0400

On Sun, 2017-03-19 at 01:51 +0000, Alejandro García Vallejo wrote:
> bar: $(@:%r=foo%z)
>         @echo End
> foobaz:
>         @echo The
> """
> GNU Make Output:
> End
> Make fails to read $@ (aka, it's empty).

That's not a bug; that's defined behavior.  From the GNU make manual:


> It’s very important that you recognize the limited scope in which
> automatic variable values are available: they only have values within
> the recipe. In particular, you cannot use them anywhere within the
> target list of a rule; they have no value there and will expand to the
> empty string. Also, they cannot be accessed directly within the
> prerequisite list of a rule. A common mistake is attempting to use $@
> within the prerequisites list; this will not work. However, there is a
> special feature of GNU make, secondary expansion (see Secondary
> Expansion), which will allow automatic variable values to be used in
> prerequisite lists.

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