[U-Boot-Users] [PATCH] Fix/workaround broken dependency handling with make 3.81

[Haavard Skinnemoen]

On Mon, 28 Aug 2006 16:35:23 +0200
Wolfgang Denk <wd at denx.de> wrote:

> Dear Haavard,
> 
> in message <20060828162247.6a33963d at cad-250-152.norway.atmel.com> you
> wrote:
> > 
> > This patch fixes the following problem:
> > 
> > make[1]: *** No rule to make target `hello_world.srec', needed by
> > `all'.
> > 
> > The problem has been reported several times before, but so far no
> > patches have been accepted and no one has fixed make. In fact, I
> > can't even find any relevant bug reports against make.
> 
> I'm sorry, but you're addressing the rong end of the problem here.
> Please submit a bug report to the make folks, and try to fix make.

If it's truly a bug in make, sure.

> > This patch takes a slightly different approach than the other
> > patches I've seen on the mailing list, as it lists the targets
> > explicitly before each of the pattern rules for the elf-, srec- and
> > bin-files. The dependencies for each target are correctly
> > specified, so we don't
> 
> Does this  mean  that  you  think  the  current  Makefile  definition
> contains  any  "incorrectly  specified"  build  rules? IF so, I would
> appreciate if you could point out where you see problems.

I'm pretty sure the problem is the "catch-all" rule for generating ELF
files:

%: %.o $(LIB)

This target matches absolutely anything, and it's not clear from the
make documentation that this is a valid rule. In fact, a target which
consists only of "%" has a special meaning, as explained in "10.6
Defining Last-Resort Default Rules" in the make manual. It does say
that a "catch-all" rule should have no prerequisites, however, so I
could be wrong about this.

> > As an added bonus, this gets rid of some duplication as each
> > architecture, cpu, board, etc. only needs to add stuff to the ELF
> > variable. The SREC and BIN variables are calculated automatically
> > from the ELF variable.
> 
> On the other hand you lose the ability to have different settings for
> SREC and BIN targets.

What kind of settings? I didn't see anything special in the existing
makefile.

If you mean different CFLAGS and such, you can still use target- or
pattern-specific variables.

> I'm not going to check in this patch, as  it  only  hides  a  serious
> problem.  If "make" is broken on a level where it's operation depends
> on the order of target names, then this should be noted, so  the  use
> of  this  broken  version  can  be  avoided, and eventually "make" be
> fixed. Even if we fix this place, we've seen a couple of other  cases
> where  similar  problems  happen with this broken version of make. It
> IMHO makes no sense to add work arounds for a broken tool.

This patch does not change the order of target names. If anything, it
makes the makefile more robust by specifying exactly what targets you
want to apply the pattern rules to.

> Let's have the tool fixed instead.

Sure, if the tool indeed is broken. Now, it's your turn to say what you
think `make' is doing wrong ;)

Haavard