How to create a makefile for several .cpp files with .h files and main.cpp without a .h

Question

I have:

main.cpp 
distance.cpp
distance.h
adjacencyList.cpp
adjacencyList.h

Here is my makefile:

all: distance main adjacencyList
    g++ distance.o main.o adjacencyList.o

main.o: main.cpp
    g++ main.cpp -lstdc++

adjacencyList.o: adjacencyList.cpp
    g++ adjacencyList.cpp -lstdc++

distance.o: distance.cpp
    g++ distance.cpp -lstdc++

clean:
    rm -rf *.o all

I am getting this error. So I'm pretty sure I'm doing something wrong with main because it is not a class like the other two and does not have a .h file.

enter image description here

Update:

After trying Ben Voigt's solution I am getting 1 error:

enter image description here

Does the following command work? g++ distance.cpp adjacencyList.cpp main.cpp -lstdc++ — nrcrast
– nrcrast, Commented Oct 10, 2014 at 5:21
No, I get bunch of warnings and then I get 3 errors : main.cpp:27: error asystema was not declared in this scope main.cpp:70: error: aatoia was not declared in this scope — Elephant
– Elephant, Commented Oct 10, 2014 at 5:27
@Elephant: Then you need to add #include <stdlib.h> to main.cpp After that, does it work? — Ben Voigt
– Ben Voigt, Commented Oct 10, 2014 at 5:30
Also, you eventually want to switch from atoi() to strtol()... the error handling is tons better. — Ben Voigt
– Ben Voigt, Commented Oct 10, 2014 at 5:31
I'm still getting a few warnings and 1 error (.text+0x20): undefined reference to 'main' Newline: collect2: ld returned 1` exit status — Elephant
– Elephant, Commented Oct 10, 2014 at 5:38

Ben Voigt · Accepted Answer · 2014-10-10 05:25:23Z

1

Your rules to create object files are missing the -c option, for "compile only". So they are trying to link, and failing because there is no main().

Then, your all target names an executable for each of the compilation units. Again, that's wrong because they don't all have main(). You should have only one executable. all should also be configured as a phony target, because it doesn't build an actual file named all.

All your rules are failing to control the name of the output file.

All your rules are failing to pass flags.

Your rules are missing dependencies on the headers, so editing headers won't cause the right files to be recompiled.

Really, you should get rid of the compile and link rules and let make use its built-in ones. Focus on your build targets and dependencies.

Your end makefile should look something like this (of course, using spaces not tabs)

all : main

.PHONY : all clean

CC = g++
LD = g++

main : main.o adjacencyList.o distance.o

main.o: main.cpp adjacencyList.h distance.h

adjacencyList.o: adjacencyList.cpp adjacencyList.h

distance.o: distance.cpp distance.h

clean:
    rm -rf *.o main

answered Oct 10, 2014 at 5:25

Ben Voigt

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2 Comments

Elephant Over a year ago

Thank you, I will look over these points. Since I've only looked at make files for a few hours, I'm basically trying to get a simple makefile working for a homework.

Elephant Over a year ago

I tried your solution and I am still getting one error that I am attempting to solve. It is in my updated question if you have time to look at it. Thanks.

Damien Saint-Macary · Accepted Answer · 2014-10-10 05:15:48Z

0

Wild guess: it is possible you are missing a semi-colon somewhere before including adjacencyList.h. Check each header files and make sure each class definition is properly terminated with a semi-colon

answered Oct 10, 2014 at 5:15

Damien Saint-Macary

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4 Comments

Elephant Over a year ago

Checked: my includes are all like 3rd-4th line down. So no semicolons missing.

Damien Saint-Macary Over a year ago

Good catch Ben. I didn't pay attention to that

Damien Saint-Macary Over a year ago

@elephant, aren't you missing some -c in your makefile (i.e. g++ -c distance.cpp for distance.o)?

Elephant Over a year ago

no, I am using -lstdc++ instead of -c You can look at my make file in my question.

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