Re: why does touching Makefile allow make to know how to build dependency?

[Luke Shumaker]

I'm willing to write that off as a fault belonging to his email editor;
otherwise I would expect make to bork about a syntax error.

The problem is that recursive make doesn't track dependencies between
instances of make.  However, it is hard to diagnose, because you have
fabricated the error message.  I suspect that it is actually closer to
one of the following:

(example 1)
make: *** No rule to make target `subdir/outfile', needed by 
`subdir/anotherFile'.  Stop.
(example 2)
make[1]: *** No rule to make target `outfile', needed by `anotherFile'.  Stop
make[1]: Leaving directory `/path/to/subdir'

If it is closer to example 2, I have no idea.

If it is closer to example 1, the problem is that it doesn't know to
look in subdir/Makefile for the dependencies.  You probably have
something like this in the top-level Makefile:

subdir/%: subdir/Makefile
        $(MAKE) -C subdir $*

Fix this by changing it to

subdir/%: subdir/ subdir/Makefile
        $(MAKE) -C subdir $*

This way, subdir/Makefile will be checked whenever anything in subdir/
changes, not just when subdir/Makefile changes.  Leaving the
subdir/Makefile bit prevents it from going into non-make directories.

I hope this helps.

-- 
~ LukeShu
http://lukeshu.ath.cx


On Fri, 2011-03-04 at 10:45 +0100, Erik Rull wrote:
> Graham Menhennitt wrote:
> > In a Makefile in a subdirectory of our top level directory, I have some
> > rules:
> >
> >
> > outfile: infile
> >
> > cmd<  infile>  outfile
> >
> >
> >
cmd < infile > outfile

> > anotherFile: outfile
> >
> 
> Have you considered newlines and tabs set correctly?
> 
> It should look like this:
> outfile: infile
>          cmd <  infile > outfile
> (where the spaces before cmd must be a tab char!)
> No blank line between the first and the second line.
> 
> > Regards,
> >
> >                  Graham
> 
> Best regards,
> 
> Erik
> 
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