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

From: SF Markus Elfring
Subject: Re: Difficulties from the combination of functions "call" and "eval"
Date: Sun, 18 Jan 2015 22:28:29 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0

> Without knowing exactly what you mean by "handling of rules with
> multiple output files" I can't say for sure, but I think it's unlikely
> that $(eval ...) can help with this.

A lot of rules can come into the situation to fiddle with multiple
output files easily.

* Specification of standard output files and standard error channels
  for shell commands

* The database "SQLite" can create its storage file while also
  exporting data to another file.

* I need to split an input file into several smaller files.

> Just to be clear, you cannot create new rules, or add to the targets or
> prerequisites of existing rules, using $(eval ...) _inside a recipe_.

I'm sorry that I needed a bit longer to realise this fact.

> This means the ONLY time setting a variable from within a recipe is
> helpful is if the only place you need to use that variable is INSIDE
> some other recipe that has not been run yet.

I imagine that conditional evaluation of recipes will be possible somehow,
wont it?


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