Re: Recursively making directories

[John Graham-Cumming]

Norman Wilson wrote:
> After working this out I had another flash of inspiration. I can make
> each directory depend on it's parent and thus do away with the -p flag
> to mkdir:
>
> %/.: | %/../.
>         mkdir $(@D)
>
> However this doesn't work. So is this a bug or a feature. If it's a
> feature can someone explain the rules.

Suppose that you write

foo/bar/baz: | foo/bar/.

and run it.  Then the % matches against foo/bar with order-only 
prerequisite foo/bar/../. which GNU make then tries to build, but it 
_does not_ collapse the path and hence cannot find a rule to make that.

The other problem is that GNU Make also avoid recursing through the same 
rule and hence even if you did make this 'work' (say by wrapping the 
prerequisite in $$(realpath) and using second expansion) it still 
wouldn't work.

I guess -p doesn't look so bad after all.

BTW.  If you are interested in directory creation ideas you can read my 
column in CM Basics 'Making directories in GNU Make' here: 
http://www.cmcrossroads.com/content/view/6936/120/

John.
--
John Graham-Cumming
address@hidden

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