make(1) guru question

[Luigi Rizzo]

On Tue, Apr 06, 2004 at 08:26:00PM +0200, Jens Schweikhardt wrote:
> Fellow hackers,
> 
> suppose you have a long list of files in a make variable V, exceeding
> kern.argmax. This means there is no way you can write a rule where $(V)
> is a command argument in any way shape or form. There is also no way to
> pass the value of V to xargs that I know of. For example with this

depending on the use, you might use something like

	make -V variable_name | xargs ...

within the makefile. I got the suggestion from someone long ago
when I had this problem with src/sys/conf/Makefile.i386

cheers
luigi

> Makefile:
> 
> 	# Make V exceed kern.argmax (64K).
> 	V != jot 12440
> 	all:
> 		@ echo $(V)
> 
> This fails with
> 
> 	echo:Argument list too long
> 	*** Error code 1
> 
> Furthermore the workaround of creating a process for each file in V with
> 
> 	V != jot 12440
> 	all:
> 	.for v in $(V)
> 		@ echo $(v)
> 	.endfor
> 
> is not acceptable because it creates too much overhead for process
> creation (think of echo being an expensive command.) Question: is there
> any other way (short of increasing kern.argmax) to maybe divide and
> conquer the V contents by use of substitution magic? I'm thinking of
> something along repeatedly cramming N items in some variable and then
> calling echo less often.
> 
> The original problem can be found in
> http://www.freebsd.org/cgi/query-pr.cgi?pr=ports/52765
> 
> Regards,
> 
> 	Jens
> -- 
> Jens Schweikhardt http://www.schweikhardt.net/
> SIGSIG -- signature too long (core dumped)
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