[LLVMdev] Usage of /dev/null in makefiles wrong

Reid Spencer rspencer at reidspencer.com
Mon Jul 23 01:19:14 PDT 2007


Holger,

I looked into it a bit. Its to prevent a message like this:

Makefile:1: no file name for `-include'

on the first build (when $(DependFiles) is empty). I changed the line
to:

-include $(DependFiles) ""

which should work because although "" is not a valid file name, the
depend files will have already been included by the time it gets to the
error, which it supresses anyway.

Reid.

On Mon, 2007-07-23 at 01:10 -0700, Reid Spencer wrote:
> Hi Holger,
> 
> On Mon, 2007-07-23 at 09:28 +0200, Holger Schurig wrote:
> >   /usr/src/llvm/llvm$ make
> >   make: Warning: File `/dev/null' has modification time 4.9e+03 s 
> > in the future
> >   make[1]: Entering directory `/usr/src/llvm/llvm/lib/System'
> >   ...
> > 
> > At the end of the compilation it emits something about clock skew
> > detected.
> > 
> > The time of /dev/null on my box is weird because of udev and/or 
> > time local settings. When it's created, the init scripts didn't 
> > have set the right locale. So in the first few hours after I 
> > turned my box on, it's timestamp is in the future.
> > 
> > But hey, it's odd that /dev/null is a "make" target anyway.
> 
> Three years I've been looking at these makefiles and I never noticed
> that before. Truly bizarre.
> > 
> > 
> > 
> > When I change line 1474 in Makefile.rules from
> > 
> >   -include /dev/null $(DependFiles
> > 
> > to
> > 
> >   -include $(DependFiles
> 
> Yup, works for me too. I think someone was trying to get around
> $(DependFiles) being empty, but that's what the - is for !
> 
> Reid.
> 
> > 
> > then this strange and weird warning vanishes.
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