>>>>> "Lars" == Lars J Aas <[EMAIL PROTECTED]> writes:
Tom> How could we fix it? I mean, conceptually.
First off, let me just say that I was considering a larger problem. I
was thinking about how to solve the exponential explosion problem for
any random variable whose contents we cared about.
But I think you're right in that it is most important for _SOURCES,
and fixing it there would certainly help.
Lars> One thing is to change how the *_OBJECTS variables are set up.
Lars> For each object that depends on some conditional, autogenerate a
Lars> unique variable name, and set up assignment to it above the
Lars> *_OBJECTS variable with only those conditionals that are
Lars> relevant.
Suppose we are looking at `windows.c'. Doesn't computing the
conditions under which windows.c is built require us to look at every
value hello_SOURCES can take? Thus hitting the exponential?
However, I think we might be able to do it by looking at variables and
not objects or conditions. In fact I think that is what your first
example (the one you said was wrong) did:
Lars> if COND_WINDOWS
Lars> GUISOURCE = windows.c windows.h
Lars> else
Lars> GUISOURCE = gtk.c gtk.h
Lars> fi
Lars> bin_PROGRAMS = hello
Lars> hello_SOURCES = \
Lars> $(GUISOURCE) \
Lars> algorithm.c \
Lars> algorithm.h
Lars> @COND_WINDOWS_TRUE@automake_obj1 = windows.lo
Lars> @COND_WINDOWS_FALSE@automake_obj1 = gtk.lo
Here automake_obj1 is the "renamed" GUISOURCE.
Now suppose GUISOURCE is defined in a more complex way:
if BAR
extra = extra.c
endif
if COND_WINDOWS
GUISOURCE = $(extra) windows.c windows.h
else
GUISOURCE = gtk.c gtk.h $(extra)
endif
Then we generate:
@COND_BAR_TRUE@automake_obj2 = extra.o
@COND_BAR_FALSE@automake_obj2 =
@COND_WINDOWS_TRUE@automake_obj1 = $(automake_obj2) windows.lo
@COND_WINDOWS_FALSE@automake_obj1 = gtk.lo $(automake_obj2)
The idea here is that we only have to transform each variable
containing sources a single time (per program or library -- we have to
name objects different if there are per-exe flags in effect). So the
behavior will never be exponential.
Right now I don't see any problem with this approach. We do need to
traverse all the objects for a given program, because we need to know
the type of each one to determine the correct linker. But we can
still compute that with the above.
Unfortunately, looking at handle_single_transform_list and
handle_source_transform, I think this is going to be a fairly major
piece of surgery. These functions aren't very well factored, at least
not in terms of the modification at hand.
Comments?
Tom
