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Date:      Sat, 17 Oct 2015 11:29:33 -0400
From:      "John D. Hendrickson" <johnandsara2@cox.net>
To:        Bryan Drewery <bdrewery@FreeBSD.org>
Cc:        arch@FreeBSD.org
Subject:   Re: make -n -n
Message-ID:  <5622695D.6040700@cox.net>
In-Reply-To: <561F3406.9050906@FreeBSD.org>
References:  <561F3406.9050906@FreeBSD.org>

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Bryan Drewery wrote:
> Does anyone consider 'make -n -n' a thing for top-level builds?
> 
> We have this ${_+_} thing in Makefiles that used to expand to '+' if you
> gave '-n -n'.  This was so just 1 '-n' would just show what the
> top-level Makefile would do:
> 
> ~/svn/clean2 # make -n includes
> cd /root/svn/clean2; PATH=/sbin:/bin:/usr/sbin:/usr/bin make -m
> /root/svn/clean2/share/mk -f Makefile.inc1 TARGET=amd64
> TARGET_ARCH=amd64 includes
> 
> Versus the more expected (at least for bmake) -n behavior of traversing
> sub-makes:
> 
> ~/svn/clean2 # make -n -n includes
> ===> lib (includes)
> ===> lib/csu (includes)
> ===> lib/csu/amd64 (includes)
> ===> lib/libcompiler_rt (includes)
> ===> lib/libc (includes)
> ===> lib/libc/tests (includes)
> ===> lib/libc/tests/tls_dso (includes)
> ===> lib/libc/tests/c063 (includes)
> etc...
> 
> Note the actual output may be off due to local changes, but the point is
> that -n with bmake is documented to run sub-makes with -n as well, so it
> calls right down the chain showing all build commands without taking any
> real actions.
> 
> Bmake added a '-N' flag that essentially does the hack that we've put
> into our top-level Makefile - it doesn't run sub-makes.
> 
> 
> So having said all of that, the ${_+_} never expands anymore since
> r251748 (June 2013). The act of it working in top-level has only been
> fixed since r288391 (September 2015).
> 
> Given it was broken for this long period I assume no one uses '-n -n' or
> even knew about it.
> 
> I would like to remove it (-n -n and _+_) and just use the (bmake)
> documented -n and -N flags and use '+' everywhere appropriate. Note that
> we use .MAKE in some targets that achieves largely the same thing, but
> many sub-make calls don't have a .MAKE and lack a proper '+' to recurse
> in Makefile.inc1.
> 

if you take a Makefile for older pmake and run it with newer - there is 
no telling what might happen (unless of course it's already been tried)

no telling




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