How to create a CMake file from an existing Makefile?

Question

I am trying to migrate my C++ code to CLion on Mac OSX, but I am new to CMake. I have a C++ code, which has been tested in Eclipse and works successfully. In particular, I have created the Eclipse project by setting the project properties according to the following Makefile.

SYSTEM = x86-64_osx LIBFORMAT = static_pic CPLEXDIR = /Users/soheilmn/Applications/IBM/ILOG/CPLEX_Studio1271 CONCERTDIR = /Users/soheilmn/Applications/IBM/ILOG/CPLEX_Studio1271/concert # --------------------------------------------------------------------- # Compiler selection # --------------------------------------------------------------------- CCC = clang++ -O0 # --------------------------------------------------------------------- # Compiler options # --------------------------------------------------------------------- CCOPT = -m64 -O -fPIC -fexceptions -DNDEBUG -DIL_STD -stdlib=libc++ # --------------------------------------------------------------------- # Link options and libraries # --------------------------------------------------------------------- CPLEXBINDIR = $(CPLEXDIR)/bin/$(BINDIST) CPLEXLIBDIR = $(CPLEXDIR)/lib/$(SYSTEM)/$(LIBFORMAT) CONCERTLIBDIR = $(CONCERTDIR)/lib/$(SYSTEM)/$(LIBFORMAT) CCLNDIRS = -L$(CPLEXLIBDIR) -L$(CONCERTLIBDIR) CCLNFLAGS = -lconcert -lilocplex -lcplex -m64 -lm -lpthread -framework CoreFoundation -framework IOKit -stdlib=libc++ all: make all_cpp execute: all make execute_cpp CONCERTINCDIR = $(CONCERTDIR)/include CPLEXINCDIR = $(CPLEXDIR)/include CCFLAGS = $(CCOPT) -I$(CPLEXINCDIR) -I$(CONCERTINCDIR)

Here is what I have created so far for the CMakeLists.txt file.

cmake_minimum_required(VERSION 3.9) project(SFCNF CXX) set(CMAKE_CXX_STANDARD 11) include_directories(/Users/soheilmn/Applications/IBM/ILOG/CPLEX_Studio1271/cplex/include) include_directories(/Users/soheilmn/Applications/IBM/ILOG/CPLEX_Studio1271/concert/include) set(CMAKE_CXX_FLAGS "-O0 -c -m64 -fPIC -DNDEBUG -DIL_STD -stdlib=libc++") link_directories("/Users/soheilmn/Applications/IBM/ILOG/CPLEX_Studio1271/concert/lib/x86-64_osx/static_pic") link_directories("/Users/soheilmn/Applications/IBM/ILOG/CPLEX_Studio1271/cplex/lib/x86-64_osx/static_pic") add_executable(SFCNF "/Users/soheilmn/CLionProjects/SFCNF/main.cpp") target_Link_Libraries(SFCNF "-lconcert -lilocplex -lcplex -m64 -lm -lpthread -framework CoreFoundation -framework IOKit -stdlib=libc++")

In CLion, when I click on the "Build" button, I see "Built target SFCNF" message (with a number of warnings). But, when I run the program, I see the following message:

"File not found: /Users/soheilmn/CLionProjects/SFCNF/cmake-build-debug/SFCNF"

Can anyone please tell me what I am missing here? Thanks!

Update: I edited my CMake file as follows.

cmake_minimum_required(VERSION 3.9) project(SFCNF CXX) set(CMAKE_CXX_STANDARD 11) add_executable(SFCNF main.cpp)

With a simple Hello World program, my C++ code now works in CLion. However, when I set the compiler options like below

cmake_minimum_required(VERSION 3.9) project(SFCNF CXX) set(CMAKE_CXX_STANDARD 11) set(CMAKE_CXX_FLAGS "-O0 -c -m64 -fPIC -DNDEBUG -DIL_STD -stdlib=libc++") add_executable(SFCNF main.cpp)

CLion produces a number of warnings as follows.

/Applications/CLion.app/Contents/bin/cmake/bin/cmake --build /Users/soheilmn/CLionProjects/SFCNF/cmake-build-debug --target SFCNF -- -j 2 [ 50%] Linking CXX executable SFCNF clang: warning: -Wl,-search_paths_first: 'linker' input unused [-Wunused-command-line-argument] clang: warning: -Wl,-headerpad_max_install_names: 'linker' input unused [-Wunused-command-line-argument] clang: warning: CMakeFiles/SFCNF.dir/main.cpp.o: 'linker' input unused [-Wunused-command-line-argument] clang: warning: argument unused during compilation: '-O0' [-Wunused-command-line-argument] clang: warning: argument unused during compilation: '-fPIC' [-Wunused-command-line-argument] clang: warning: argument unused during compilation: '-D NDEBUG' [-Wunused-command-line-argument] clang: warning: argument unused during compilation: '-D IL_STD' [-Wunused-command-line-argument] clang: warning: argument unused during compilation: '-stdlib=libc++' [-Wunused-command-line-argument] clang: warning: argument unused during compilation: '-g' [-Wunused-command-line-argument] [100%] Built target SFCNF

Moreover, now if I modify my program to print another message, CLion keeps running the previous Hello World program as if I have not modified anything in the main.cpp file.

First, don't use absolute paths. Source files should be specified relative to the CMakeLists.txt file. Ignore extra libraries at first and get it just compiling. Then try using find_package or find_library to find your dependencies. $ENV{HOME} can be used in hint paths. — John
– John, Commented Jan 12, 2018 at 17:47
@John Thanks! I just don't understand how CMake works within CLion. Now, I only included "cmake_minimum_required(VERSION 3.9) project(SFCNF CXX), set(CMAKE_CXX_STANDARD 11) add_executable(SFCNF main.cpp)" and in the main.m file, I have a simple hello world program. It woks fine! Then I add another command {set(CMAKE_CXX_FLAGS "-O0 -c -m64 -fPIC -DNDEBUG -DIL_STD -stdlib=libc++")} which produces warning. Then, I can still run the code, but any change in the main.cpp file will be ignored. Does that mean CLion/CMake does not build if there is any warning? (Thanks for being patient with me!) — Soheilmn
– Soheilmn, Commented Jan 12, 2018 at 20:03
On Stack Overflow comments are not for a code. Update your question post with current problem. And explain what but any change in the main.cpp file will be ignored means. — Tsyvarev
– Tsyvarev, Commented Jan 12, 2018 at 21:07
Here is a similar question with a very helpful answer. stackoverflow.com/questions/58244727/… — Soheilmn
– Soheilmn, Commented Oct 8, 2019 at 17:59

ComicSansMS · Accepted Answer · 2018-01-15 08:54:00Z

Do not manually set compile flags in CMake like that.

Instead, use the respective CMake features to achieve what those flags where supposed to do:

-O0 the level of optimization is typically determined by the CMAKE_BUILD_TYPE. Note that this is a variable that will be set by the user when invoking CMake, so you should only ever read from that variable in the CMakeLists.txt.
-c CMake properly separates compile and link steps, just never pass this option.
-m64 The machine type is determined by the compiler being used (for Makefiles) or the generator (on Visual Studio). If you need to manually choose a different machine type, you will need a toolchain file. Unless you are cross-compiling, you almost certainly just want to skip this option.
-fPIC This is done by setting the POSITION_INDEPENDENT_CODE target property. You can also set this globally for all targets by setting the CMAKE_POSITION_INDEPENDENT_CODE variable.
-DNDEBUG This is again set automatically based on the CMAKE_BUILD_TYPE.
-DIL_STD Use target_compile_definitions to set preprocessor defines.
-stdlib=libc++" First be sure that you actually need this. This is again a toolchain dependent option, and one that highly depends on the build environment. So you will want to at least escape it behind a generator expression to make sure it is only invoked for the toolchains where it applies. You might even consider moving it to a toolchain file as well.

All of that being said: There is no easy 1:1 conversion from Makefiles to CMake.

Both systems have vastly different scopes and use completely different idioms. In particular, CMake needs to be portable to a lot of underlying build systems, so a lot of the shortcuts that make can use are not supported by CMake. For instance, the link_directories approach that you used is usually a really bad idea in CMake. Be sure you first get familiar with how CMake does these things before proceeding.

Thank you very much for all these information! As I mentioned I am a newcomer to CMake world, so I will try to use your advices in making my CMake file.

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