From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Monjalon <thomas@monjalon.net>
Subject: Re: [PATCH v3 7/8] mk: sort object files when building
	deps lists
Date: Tue, 27 Jun 2017 15:52:24 +0200
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References: <20170623181616.16981-1-lboccass@brocade.com>
 <2558671.pWjLEmoHCY@xps> <1498560192.14026.11.camel@brocade.com>
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To: Luca Boccassi <lboccass@brocade.com>
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27/06/2017 12:43, Luca Boccassi:
> On Tue, 2017-06-27 at 01:20 +0200, Thomas Monjalon wrote:
> > 23/06/2017 20:41, lboccass@brocade.com:
> > > From: Luca Boccassi <luca.boccassi@gmail.com>
> > > 
> > > In order to achieve reproducible builds, always use the same
> > > order when listing object files to build dependencies lists.
> > > 
> > > Signed-off-by: Luca Boccassi <luca.boccassi@gmail.com>
> > > ---
> > >  mk/rte.app.mk     | 4 ++--
> > >  mk/rte.hostapp.mk | 4 ++--
> > >  mk/rte.shared.mk  | 4 ++--
> > >  3 files changed, 6 insertions(+), 6 deletions(-)
> > > 
> > > --- a/mk/rte.app.mk
> > > +++ b/mk/rte.app.mk
> > > @@ -263,8 +263,8 @@ LDLIBS_NAMES += $(patsubst -Wl$(comma)-
> > > l%,lib%.a,$(filter -Wl$(comma)-l%,$(LDLIB
> > >  
> > >  # list of found libraries files (useful for deps). If not found,
> > > the
> > >  # library is silently ignored and dep won't be checked
> > > -LDLIBS_FILES := $(wildcard $(foreach dir,$(LDLIBS_PATH),\
> > > -	$(addprefix $(dir)/,$(LDLIBS_NAMES))))
> > > +LDLIBS_FILES := $(sort $(wildcard $(foreach dir,$(LDLIBS_PATH),\
> > > +	$(addprefix $(dir)/,$(LDLIBS_NAMES)))))
> > 
> > You cannot sort libraries.
> > Check - for instance - this comment above in this file:
> > 	# Eliminate duplicates without sorting, only keep the last
> > occurrence
> > 	filter-libs = \
> 
> Not sure I follow - what's the reason for avoiding to sort the list of
> libs to link against?

Sorry, the ordering issue is with LDLIBS not LDLIBS_FILES.

> > Why sorting them?
> > What is random in libraries list?
> 
> The issue is that the output of wildcard is not fully deterministic. It
> can depend on the filesystem, and even on the locale settings [1].
> Before GNU Make 3.82 (2009) it used to automatically sort the output,
> but that was removed (to make it faster... sigh). [2]

It is not a true wildcard here. It is just filtering files which
do not exist.
I think you do not need this patch for deterministic build.