mingw-users

[Mingw-users] Makefile Conundrum

[Danuvius <dan...@gm...>]

Greetings!

I have a bit of a makefile issue which I've failed not only to solve
but even to understand.

The below seems to work fine (pairing the proper .cpp file with the
corresponding .o file) when I don't do the monkeying around to get the
.o files to end up in a separate output directory.

But once the output directory is prefixed to the .o files, every
object files is compiled by taking the first file (main.cpp) as the
source... which, obviously leads to nothing workable.

I searched google and attempted to make sense of autovariables via the
makefile documentation... but still don't understand why the observed
outcome is happening.

However I have a nagging suspicion that this is one of those situation
that may be solved by changing a single character, or, at most, a few
on a single line.

I'd be grateful for any assistance, or even suggestions pointing me in
new directions toward figuring it out on my own.

Thank you in advance! -- Danuvius

-----
CC=g++

INDIR=./src
OUTDIR=./bin

INCLUDES=-I./sfml-1.6/include  -I./lua-5.2.0/src
LINCLUDES=-L./sfml-1.6/lib -L./lua-5.2.0/src

LIBRARIES=-lsfml-graphics-s -lsfml-window-s -lsfml-system-s -llua52

CFLAGS=-c $(INCLUDES) -Wall -O3 -o $(OUTDIR)
LFLAGS=-static-libgcc -static-libstdc++ $(LINCLUDES) $(LIBRARIES)

TSOURCES=main.cpp Logger.cpp
TOBJECTS=$(TSOURCES:.cpp=.o)

SOURCES=$(addprefix $(INDIR)/,$(TSOURCES))
OBJECTS=$(addprefix $(OUTDIR)/,$(TOBJECTS))

EXECUTABLE=$(OUTDIR)/vilag

all: $(SOURCES) $(EXECUTABLE)

run:
       $(EXECUTABLE)

$(EXECUTABLE): $(OBJECTS)
       $(CC) $(LFLAGS) $(OBJECTS) -o $@

$(OBJECTS): $(SOURCES)
       $(CC) $(CFLAGS) $< -o $@

clean:
       rm -rf $(OUTDIR)/*.o
-----

Re: [Mingw-users] Makefile Conundrum

[Keith M. <kei...@us...>]

On 26/05/12 15:22, Danuvius wrote:
> I have a bit of a makefile issue which I've failed not only to solve
> but even to understand.
> 
> The below seems to work fine (pairing the proper .cpp file with the
> corresponding .o file) when I don't do the monkeying around to get the
> .o files to end up in a separate output directory.
> 
> But once the output directory is prefixed to the .o files, every
> object files is compiled by taking the first file (main.cpp) as the
> source... which, obviously leads to nothing workable.

> TSOURCES=main.cpp Logger.cpp
> TOBJECTS=$(TSOURCES:.cpp=.o)
> 
> SOURCES=$(addprefix $(INDIR)/,$(TSOURCES))
> OBJECTS=$(addprefix $(OUTDIR)/,$(TOBJECTS))

> $(OBJECTS): $(SOURCES)
>        $(CC) $(CFLAGS) $< -o $@

This is all kinds of wrong!

First, you've set up $(OBJECTS) to be a list of object file names,
each prefixed by a path name, and $(SOURCES) to be a list of source file
names, again with each prefixed by a (different) path name; now, your
predicate:

  $(OBJECTS): $(SOURCES)

makes *every* object file depend on *every* source; this is *not* what
you want!

Second, your command:

    $(CC) $(CFLAGS) $< -o $@

uses the $< autovariable in a context which is neither a suffix rule,
nor a pattern rule; this is invalid usage, since those are the *only*
contexts in which $< is strictly valid.  (In GNU make, this improper
usage does actually assign $< as the *first* prerequisite -- main.cpp in
your case, which explains why every one of your object files is compiled
from main.cpp; in most generic make implementations, $< expands to
nothing at all, when used in this invalid context).

To fix your problem, you should use a pattern rule, (which *is* a valid
context for use of $<):

  %.o: %.cpp
       $(CXX) $(CPPFLAGS) $(CXXFLAGS) -o $@ -c $<

(using $(CXX) as the preferred alias for the C++ compiler; $(CC) is
traditionally reserved for the C compiler), or, in this case, you could
just use the built-in pattern rule, by omitting *any* explicit rule for
building .o files from .cpp sources.

Now, to get your object files in a separate directory from your sources,
the method I would recommend is to have your object file directory as
the current working directory -- make a copy of, or a link to, the
Makefile within it, for convenience -- and add a VPATH or vpath
specification within that Makefile, to point to the source directory;
e.g. where you have:

  project/
     +---  src/
     |       +--- source.cpp
     +---  obj/
     |       +--- Makefile

you would add:

  VPATH = ../src

to project/obj/Makefile, then cd to project/obj to run make, (and you
*don't* muck about with all the $(addprefix ...) nonsense -- just refer
to your sources by a simple file name alone, and leave the VPATH
mechanism to add the appropriate directory prefix).

-- 
Regards,
Keith.

Re: [Mingw-users] Makefile Conundrum

[Danuvius <dan...@gm...>]

Thank you, Keith!  Both for the explanations as to what's wrong and
the suggestions for fixing it.

I now have something that appears to work as desired.

Sincerely,

Danuvius

Re: [Mingw-users] Makefile Conundrum

[NightStrike <nig...@gm...>]

On Mon, May 28, 2012 at 12:08 PM, Danuvius <dan...@gm...> wrote:
> Thank you, Keith!  Both for the explanations as to what's wrong and
> the suggestions for fixing it.
>
> I now have something that appears to work as desired.

If you felt like doing some additional work to get something that
might be easier to maintain, you can look into automake for writing
this for you.  You could achieve your original makefile by creating an
automake Makefile.am file that is as small as this:

===============
SFML = ./sfml-1.6
LUA = ./lua-5.2.0

bin_PROGRAMS = vilag

vilag_SOURCES = main.cpp Logger.cpp
vilag_CFLAGS = -Wall -O3
vilag_CPPFLAGS = -I$(SFML)/include  -I$(LUA)/src
vilag_LDADD = -L$(SFML)/lib -lsfml-graphics-s -lsfml-window-s
-lsfml-system-s -L$(LUA)/src -llua52
===============

That's of course completely untested, and you need to pair it with a
configure.ac file, but that's easily created automatically with
autoscan.

What you have works, so you obviously don't have to, but you might
find that you like it, so I figure I'll toss it out there.

Cheers!