Re: newbie g++ / gcc makefile???

[Martin Jørgensen]

Ulrich Eckhardt wrote:
> Martin Jørgensen wrote:
>
> > I just made my first C++/C combined project and it works on windows. Now 
> > I want it to work on linux. So I have changed main.c to main.cpp 
>
>
> I don't think you mean that, but anyways: there is no reason to name things
> differently in order to compile them under Linux.

Oh, I think this might be a misunderstanding because also on windows, 
the main.c is now called main.cpp - if that was what you were referring 
to...... I read that it was necessary to have the main() function in 
C++, in order to mix those languages...

> > and also have a new C++-function in the file: output_energy.cpp. The 
> > rest are C-functions.
> >
> > How should the make-file be modified? I know that main must be processed 
> > by a C++-compiler so I changed CC = gcc to CC = g++ in the makefile 
> > below
>
>
> Nope, that's wrong:
> 1. You don't set CC in the makefile, 'make' knows quite well the name of
> the C compiler and this disallows overriding by the user (e.g. to select a
> specific version).

Thanks.

> 2. The C++ compiler is CXX and also known to 'make'
>
>
> > .c.o:
> >         $(RM) $@
> >         @ #
> >         $(CC) -c $(CFLAGS) $(SRC)/$*.c
>
>
> # similarly for C++
> .cpp.o:
>     $(CXX) $(CXXFLAGS) -c $(SRC)/$*.c
>
> However, I think the placeholder for the input file is $< (i.e. the one
> currently being compiled), see the manual.

The "gnu make manual" called make.pdf from www.gnu.org, right? I 
downloaded it...

> >     PROTO_DEFINES = -DFUNCPROTO=15 -DNARROWPROTO
> >       STD_DEFINES = -Dlinux -D__i386__ -D_POSIX_C_SOURCE=199309L 
>
>                        ^^^^^^^^^^^^^^^^^^^
> Don't do that either, it make the makefile non-portable and those (or
> similar ones) should be defined by the compiler (assuming you are using it
> under Linux and on an x86 architecture).

I just stole it from somewhere, but I don't know what it means... Now I 
deleted it completely.

> > CFLAGS = $(PROTO_DEFINES) $(STD_DEFINES) -g -W -Wall -ansi 
>
>
> The -W is deprecated and now called -Wextra, IIRC.

I think you're right...

> > simulate:  $(OBJ)
> >         $(RM) $@
> >         $(CC) -o $@ -g -W -Wall -ansi -pedantic -Wformat-nonliteral[...]
>
>
> Wait a second, are you repeating all the warning settings here? Use CFLAGS

Erhm.... Perhaps I do... I wasn't really sure what this makefile did in 
the first place :-)

> instead. Anyhow, this is the linker stage, and things like '-ansi' only
> affect compilation so this doesn't make sense here anyway. Also, if you
> are linking a C++ program, you need to use CXX for that.

Hmm. Okay. So in the linker stage I need something else than CFLAGS. And 
since main() is a C++ function I need CXX to do the linking of all .o 
files, I guess...

-snip (error messages) -
....
....

> This is a result of compiling C code with a C++ compiler. C allows
> converting a void pointer to any other pointer without an explicit cast,
> C++ with its stricter type safety doesn't. Use a C compiler or fix the
> code. Or, in general, don't blindly use a C++ compiler, there is no reason
> for it.

Got it.

> > What do I do? I think I need to tell my makefile that most of the files 
> > should be compiled by a C-compiler (gcc?) and main.cpp and the other 
> > .cpp files should be compiled with g++?
>
>
> Right, I hope I showed you how to separate those.

Yep, I think you helped me a lot... I think I'm very close to being able 
to compile my newly transformed C++ (originally a C)-program:


--- new makefile ---
    RM = rm -f
        SRC   = ./
        SYS_LIBRARIES = -lm

        CFLAGS = -g -c -Wextra -Wall -ansi -pedantic 
-Wformat-nonliteral -Wcast-align -Wpointer-arith -Wbad-function-cast 
-Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations -Winline 
-Wundef -Wnested-externs -Wcast-qual -Wshadow -Wconversion 
-Wwrite-strings -Wno-conversion -ffloat-store -O0

        CXXFLAGS = -g -c -O0 -Wall


# output program (executable file name)
PGM = simulate

# files that must be made by C-compiler (CC)
OBJ_C = \
        array_functions.o \
        band_solve.o \
        check_errors.o \
        import_data.o \
        memory_functions.o \
        mesh_functions.o \
        polymesh.o \
        porosities.o \
        read_materials.o \
        result_output.o

# files that must be made by C++-compiler (CXX)
OBJ_CPP = \
        main.o \
        output_energy.o

simulate: $(OBJ_C) $(OBJ_CPP)
        $(RM) $@
        $(CC) -o $@ $(CFLAGS) $(OBJ_C) $(LIBPATH) $(SYS_LIBRARIES) 
Solverlib.a
        $(CXX) -o $@ $(CXXFLAGS) $(OBJ_CPP) $(LIBPATH) $(SYS_LIBRARIES) 
Solverlib.a

        etags `find -iname "*.c"` `find -iname "*.cpp"` `find -iname "*.h"`


clean::
        $(RM) simulate *.CKP *.ln *.BAK *.bak *.o *.u a.out core errs 
,* *~ .emacs_* tags TAGS make.log MakeOut "#"*

----

So I cleaned up a lot... Was also tired of not understanding what was in 
it... When I try to compile my C++ program (using many C-functions) I get:

---- output ---
....
....
....
cc -g -c -Wextra -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align 
-Wpointer-arith -Wbad-function-cast -Wmissing-prototypes 
-Wstrict-prototypes -Wmissing-declarations -Winline -Wundef 
-Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings 
-Wno-conversion -ffloat-store -O0   -c -o result_output.o result_output.c
g++ -g -c -O0 -Wall   -c -o main.o main.cpp
g++ -g -c -O0 -Wall   -c -o output_energy.o output_energy.cpp
rm -f simulate
cc -o simulate -g -c -Wextra -Wall -ansi -pedantic -Wformat-nonliteral 
-Wcast-align -Wpointer-arith -Wbad-function-cast -Wmissing-prototypes 
-Wstrict-prototypes -Wmissing-declarations -Winline -Wundef 
-Wnested-externs -Wcast-qual -Wshadow -Wconversion -Wwrite-strings 
-Wno-conversion -ffloat-store -O0 array_functions.o band_solve.o 
check_errors.o import_data.o memory_functions.o mesh_functions.o 
polymesh.o porosities.o read_materials.o result_output.o   -lm Solverlib.a
cc: array_functions.o: linker input file unused because linking not done
cc: band_solve.o: linker input file unused because linking not done
cc: check_errors.o: linker input file unused because linking not done
..... etc......
... (more lines with linking not done)
...
----

So, what is the (hopefully finally?) push in the right direction I need 
now? Comments/suggestions are appreciated. I also would like to have the 
g++ warning level turned up to the "ultimate maximum level", if possible.


Best regards
Martin Jørgensen

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