Re: Make question: Specify which CXXFLAGS to use

[Glynn Clements]

"William Payne" <mikas493_no_spam@student.liu.se> writes:

> Hello, consider this Makefile:
>
> CXX = g++
> LD = g++
> CXXFLAGS_DEBUG = -Wall -W -ansi -pedantic -g -ggdb -c -o
> CXXFLAGS_RELEASE = -Wall -W -ansi -pedantic -O -c -o
> LDFLAGS_DEBUG = -mwindows -lole32 -L/usr/local/gcc-3.4.2/lib/ -o $(EXEC)
> LDFLAGS_RELEASE = -s -mwindows -lole32 -L/usr/local/gcc-3.4.2/lib/ -o 
> $(EXEC)
> EXEC = debug_file_remover
> OBJECTS = \
>  main_dialog_procedure.o \
>  selected_directory_edit_box_procedure.o \
>  winmain.o \
>  debug_file_remover.res
>
> debug: $(OBJECTS)
>  $(LD) $(OBJECTS) $(LDFLAGS_DEBUG)
>
> release: $(OBJECTS)
>  $(LD) $(OBJECTS) $(LDFLAGS_RELEASE)
>
> %.o: %.cpp
>  $(CXX) $(CXXFLAGS) $@ $<
>
> %.res: %.rc
>  windres $< -O coff -o $@
>
> clean:
>  rm -f $(OBJECTS) $(EXEC) *~ *.stackdump
>
> My problem is that depending on whether the user is doing "make debug" or 
> "make release", I want to specify which CXXFLAGS_ to use.
> Can I have a variable, say $CXXFLAGS, that I set to either $CXXFLAGS_DEBUG 
> or RELEASE as appropiate? If so, how?

It's better (and probably easier) to have separate names for the debug
and release versions of the object files, e.g.:

        DEBUG_OBJECTS = $(patsubst %.o,dbg/%.o,$(OBJECTS))
        RELEASE_OBJECTS = $(patsubst %.o,dbg/%.o,$(OBJECTS))
        
        dbg/%.o: %.cpp
                $(CXX) $(DEBUG_CXXFLAGS) -o $@ $<
        
        rel/%.o: %.cpp
                $(CXX) $(RELEASE_CXXFLAGS) -o $@ $<
        
        debug: $(DEBUG_OBJECTS)
               $(LD) $(LDFLAGS_DEBUG) $^
        
        release: $(RELEASE_OBJECTS)
               $(LD) $(LDFLAGS_RELEASE) $^

This has the advantage that "make debug ; make release" will do the
right thing, i.e. build each target from the correct set of .o files,
rather than building the release target from the pre-existing (debug)
versions of the .o files.

-- 
Glynn Clements <glynn.clements@virgin.net>