CODEWITHSUNDEEP
c++compilationmakefile
FearJoy
FearJoy

Reputation: 57

Simple makefile for C++

I am having some trouble with a programing assignment for a CS class. We were introduced to makefiles this week, but it was barely touched upon. The goal is to write a program to calculate the average and summation of user provided doubles. The program works fine with g++, but I am having issues with the makefiles.

I am working with 3 cpp files: main.cpp, average.cpp, summation.cpp. And 2 header files: average.h and summation.h

Here is one make file I have tried:

CXX = g++
CXXFLAGS = -std=c++0x -Wall -pedantic-errors -g

SRCS = summation.cpp average.cpp main.cpp 
OBJS = ${SRCS:.cpp=.o}
HEADERS = summation.h average.h

MAIN = myprog

all: ${MAIN}
    @echo   Simple compilter named myprog has been compiled

${MAIN}: ${OBJS} ${HEADERS}
    ${CXX} ${CXXFLAGS} ${OBJS} -o ${MAIN} ${OBJS}

.cpp.o:
    ${CXX} ${CXXFLAGS} -c $< -o $@

clean:
    ${RM} ${PROGS} ${OBJS} *.o *~

Errors: main.cpp:31: undefined reference to avg(double*, int)' main.cpp:32: undefined reference tosum(double*, int)'

If I run the command g++ main.cpp summation.cpp average.cpp -o main Then it will compile without any issues.

I'm not sure if I have something out of order, or if I am missing something. Looking around I've found a lot of info, but it seems to be over my head.

Upvotes: 3

Views: 3318

Answers (1)

mziccard
mziccard

Reputation: 2178

I think you have two problems here.

First, the ordering SRCS = summation.cpp average.cpp main.cpp. This causes the .o to be provided to g++ in the order summation.o average.o main.o which causes the undefined error. You want to provide them in the order main.o summation.o average.o, hence SRCS should be SRCS = main.cpp summation.cpp average.cpp.

Second, in the line: 

${CXX} ${CXXFLAGS} ${OBJS} -o ${MAIN} ${OBJS}

The second ${OBJS} is not needed.
Try the following:

CXX = g++
CXXFLAGS = -std=c++0x -Wall -pedantic-errors -g

SRCS =  main.cpp summation.cpp average.cpp
OBJS = ${SRCS:.cpp=.o}
HEADERS = summation.h average.h

MAIN = myprog

all: ${MAIN}
        @echo   Simple compilter named myprog has been compiled

${MAIN}: ${OBJS}
        ${CXX} ${CXXFLAGS} ${OBJS} -o ${MAIN}

.cpp.o:
        ${CXX} ${CXXFLAGS} -c $< -o $@

clean:
        ${RM} ${PROGS} ${OBJS} *.o *~.

Upvotes: 5

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