one makefile for 2 cpp programs

Question

Hello I need to create a makefile for 2 separated cpp programs that are in one directory. I have got this code, but it's not working correctly. The .o files do not get created.Thank you

OBJS = a b
EXEC = first_run second_run

#------ constant definitions

ALL_OBJ = $(OBJS:%=%.o)

all: $(EXEC)

clean:
    $(RM) $(EXEC) $(OBJS) $(ALL_OBJ); make all

CC = g++

DO_OBJS = $(CC) -cpp -o [email protected] [email protected]; touch $@
DO_EXEC = $(CC) -s -o $@ $(ALL_OBJ)

#------ now compile

$(OBJS):    $(@:%=%.o)
        $(DO_OBJS)

$(EXEC):    $(OBJS)
        $(DO_EXEC)

g++ -s -o first_run a.o b.o a.o: In function _start': (.text+0x0): multiple definition of _start' /usr/lib/gcc/i686-linux-gnu/4.6/../../../i386-linux-gnu/crt1.o:(.text+0x0): first defined here a.o:(.rodata+0x0): multiple definition of _fp_hw' /usr/lib/gcc/i686-linux-gnu/4.6/../../../i386-linux-gnu/crt1.o:(.rodata+0x0): first defined here a.o: In function _fini': (.fini+0x0): multiple definition of `_fini' /usr/lib/gcc/i686-linux-gnu/4.6/../../../i386-linux-gnu/crti.o:(.fini+0x0): first defined here — Natasha Levesque
– Natasha Levesque, Commented Oct 15, 2012 at 19:11
What are you trying to achieve? How do a & b relate to first_run and second_run? Is your first program supposed to be an executable called first_run? Or an executable called a? Or what? — Robᵩ
– Robᵩ, Commented Oct 15, 2012 at 19:13
I want to create a.o and b.o from one make file. first_run is for a and second for b. — Natasha Levesque
– Natasha Levesque, Commented Oct 15, 2012 at 19:15
You only want a.o and b.o? You don't want to create an executable? — Robᵩ
– Robᵩ, Commented Oct 15, 2012 at 19:17

Some programmer dude · Accepted Answer · 2012-10-15 19:36:53Z

3

There are a couple of problems with your file, but the major problem seems to be that you try to link both source files to a single executable. You have to list each program and its dependencies on its own.

Try instead this simple Makefile:

SOURCES = a.cpp b.cpp
OBJECTS = $(SOURCES:%.cpp=%.o)
TARGETS = first_run second_run

LD = g++
CXX = g++
CXXFLAGS = -Wall

all: $(TARGETS)

# Special rule that tells `make` that the `clean` target isn't really
# a file that can be made
.PHONY: clean

clean:
    -rm -f $(OBJECTS)
    -rm -f $(TARGETS)

# The target `first_run` depends on the `a.o` object file
# It's this rule that links the first program
first_run: a.o
    $(LD) -o $@ $<

# The target `second_run` depends on the `b.o` object file
# It's this rule that links the second program
second_run: b.o
    $(LD) -o $@ $<

# Tells `make` that each file ending in `.o` depends on a similar
# named file but ending in `.cpp`
# It's this rule that makes the object files    
.o.cpp:

edited Oct 15, 2012 at 19:36

answered Oct 15, 2012 at 19:14

Some programmer dude

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4 Comments

Some programmer dude Over a year ago

@NatashaLevesque Forgot to add commands for linking, please see my modified answer.

Natasha Levesque Over a year ago

makefile:16: *** missing separator. Stop.

Natasha Levesque Over a year ago

hm... still the same error makefile:16: *** missing separator. Stop.

Natasha Levesque Over a year ago

it works. changed the -rm -f $(OBJECTS) -rm -f $(TARGETS) to \rm -f $(OBJECTS) \rm -f $(TARGETS)

Robᵩ · Accepted Answer · 2012-10-15 19:16:45Z

2

KISS:

all: first_run second_run

clean:
    rm -f first_run second_run

first_run: a.c
    $(LINK.cc) $^ $(LOADLIBES) $(LDLIBS) -o $@

second_run: b.c
    $(LINK.cc) $^ $(LOADLIBES) $(LDLIBS) -o $@

answered Oct 15, 2012 at 19:16

Robᵩ

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Comments

Olaf Dietsche · Accepted Answer · 2012-10-15 19:16:32Z

0

I suggest this Makefile:

EXEC = first_run second_run
OBJS_FIRST = a.o
OBJS_SECOND = b.o

all: $(EXEC)

first_run: $(OBJS_FIRST)
    $(CXX) -o $@ $(OBJS_FIRST)

second_run: $(OBJS_SECOND)
    $(CXX) -o $@ $(OBJS_SECOND)

You don't need to define the object build, since make already knows, how to do that.

answered Oct 15, 2012 at 19:16

Olaf Dietsche

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