Re: Prime Mover v0.1

[Ralph Hempel <rhempel@...>]

David Given wrote:
> All right, try this: I have fifty files in directory A, all with .c
> extensions, that need to be built with one particular set of compilation
> options. I also have fifty files in directory B, all with .c extensions, that
> need to be built with *another* set of compilation options. How do you write a
> single makefile that deals with this cleanly?
>
> The answer is, you can't. make automatically determines what rule to apply to
> each file based on the file extension. (Actually, a file pattern. It might be
> possible to use patterns of the form 'A/%.c' and 'B/%.c', but I'd be hesitant
> to use it.) However, it only allows you to specify a *single* rule for each
> pattern. In order to solve the above problem, you have two options: firstly,
> you can specify manually which files each rule should apply to --- which
> rather defeats the purpose of make's automatic rule mechanism --- or else you
> write two makefiles, which is much less effort, but which blows a big hole in
> the dependency management.

First, dump all of the built in rules - they are for simple default
build scenarios, which yours is clearly not :-)

Then, learn to use the 'A/%.c' and 'B/%.c' patterns, and specify
what you want to do to build the .o files, and what compiler options,
like this:

CCFLAGS_A = some flag settings for scenario A
CCFLAGS_B = some flag settings for scenario B

A/%.o : %.c
	$(COMPILER_BIN)/$(CC) $(CFLAGS_A) $<

B/%.o : %.c
	$(COMPILER_BIN)/$(CC) $(CFLAGS_B) $<

I've got specific definitions for COMPILER_BIN and CC because
I use toolchains for multiple processors in my project. Talk
about flags for this set of files vs files for that set!

> It gets even worse when your two sets of files are all in *one* directory. It
> gets an order of magnitude worse when you try to bolt in automatic C
> dependency management. It gets *another* order of magnitude worse when you try
> to add support for cross-compilation. And if you try to add support for
> multi-stage compilation, make curls up in a corner and cries.

Yes, but if you talk in a quiet voice and lower yourself to its level
it will eventually come out, and then you can hit it over the head
and make it do what you want :-)

> Trust me. I know how to use make.

I think you do too, and I think we all would like a better general
purpose scripting ability for or alternative to make. But there's
a lot of inertia behind that tool....

Cheers, Ralph