User produced dependency files - possible to use them?

[Alex Hornby]

Hi,

As part of my project I have some suffix rules to produce built sources
from which I can produce automatic dependency information.

My question is - is it possible to get automake to take these user
defined auto dependencies into consideration?

What I'd envisage is being able to set a user variable in some way and
have it appended to the calculated DEP_FILES variable.

I've tried things like:

.bar.foo:
        foo2bar $<

MODULES = A.bar B.bar C.bar
USER_DEP_FILES = $(MODULES:.bar=.foodep)
DEP_FILES += $(USER_DEP_FILES)

But get the message:

pnl/Makefile.am:69: DEP_FILES must be set with `=' before using `+='

Regards,
Alex.