Converting a Makefile project to Cmake

Question

I'm learning how to use cmake for this class but the documentation is extremely verbose and dense. A lot of the tutorials are either too simple to be useful (cmake with just one file) or too complicated.

the original Makefile for the project looks like:

# Some optimization settings
# see: http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html

# Standard all target
all: hw1_p2

# Simple program to do brute-force k-nearest neighbor searches against a signature file
hw1_p2: prob2.o ParseRecord.o Sorter.o Timing.o
        g++ -o hw1_p2 prob2.o ParseRecord.o Sorter.o Timing.o

prob2.o: prob2.cpp utility_templates.hpp
        g++ -Wall -c prob2.cpp

ParseRecord.o: ParseRecord.cpp ParseRecord.hpp utility_templates.hpp
        g++ -Wall -c ParseRecord.cpp

Sorter.o: Sorter.cpp Sorter.hpp
        g++ -Wall -c Sorter.cpp

# Timing class
Timing.o: Timing.hpp Timing.cpp
        g++ -Wall -c Timing.cpp

# Clean code-derived files
clean:
        rm -f *.o hw1_p2 

The project is organized like this

• cmakelearn
  • CMakeLists.txt
  • build
  • src
    • CMakeLists.txt
    • ParseRecord.hpp
    • Timing.cpp
    • small.dat
    • Makefile
    • Sorter.cpp
    • Timing.hpp
    • utility_templates.hpp
    • ParseRecord.cpp
    • Sorter.hpp
    • prob2.cpp

So far, from the reading that I've done I understand that you need a CMakelists.txt file in every directory. The build folder is there so that I can go into it and run cmake ..

In the top-level CMakelists.txt file I have

cmake_minimum_required (VERSION 2.6)
project (CMAKETEST)
add_subdirectory(src)

and in the src dir CMakelist.txt here is my attempt:

include_directories(${CMAKETEST_SOURCE_DIR}/src)
link_directories(${CMAKETEST_BINARY_DIR}/src)

add_executable(hw1_p2 prob2.cpp ParseRecord.cpp Sorter.cpp Timing.cpp)

I don't even really know where to begin other than that. This comment from a tutorial pretty much sums up my thoughts about cmake and the documentation right now:

Not nearly detailed enough to be useful. Having said that, I don’t like CMake much anyway; too many separate, arbitrary Things you Just Have to Know. At least that’s my impression. Like, ‘add_definitions(-std=c99)’. Really? Does that name jump out at you as how to add flags to a compiler? And is ‘set(VAR a b c)’ any more intuitive than VAR=a b c or some such? Beh on the article, and on CMake. Yet I know CMake is taking the build-world by storm.

Still, I really want to learn and figure this out so any help that you can provide will be much appreciated and helpful. Thanks in advance.

Answer 1

You do not have to create cmakelists.txt files in every subdirectory. For a project that simple it should be enough to put everything into the toplevel cmakelists.txt

cmake_minimum_required (VERSION 2.6)
project (CMAKETEST C CXX)

add_executable(hw1_p2 src/prob2.cpp src/ParseRecord.cpp src/Sorter.cpp src/Timing.cpp)

this simple cmakelists.txt should get the job done.