An Introduction to CMake

© Integrated Computer Solutions, Inc. All Rights Reserved
An Introduction to CMake
Jeff Tranter <jtranter@ics.com> February, 2019
1

Agenda
What is CMake?
Features
A Simple Example
A More Complex Example
Qt Support
Qt Example
Qt Creator Support
CTest and CPack
Misc. Tips
Summary
Q&A
References
2

What is CMake?
• Cross-platform build system
• Sits on top of and leverages native build system
• Funded by KitWare
• Written in C++
• Support for Qt
• Current version 3.13.3
3

Features
• Supports:
• in place and out of place builds
• enabling several builds from the same source tree
• cross-compilation
• support for executables, static and dynamic libraries, generated files
• support for common build systems and SDKs
4

A Simple Example
CMakeLists.txt:
cmake_minimum_required(VERSION 3.0)
project(Demo1)
add_executable(Demo1 demo1.cpp)
5

A Simple Example
demo1.cpp:
#include <iostream>
int main()
{
std::cout << "Hello, world!" << std::endl;
return 0;
}
6

A Simple Example
In source build:
% cd demo1
% ls
CMakeLists.txt demo1.cpp
7

A Simple Example
% cmake .
-- The C compiler identification is GNU 7.3.0
-- The CXX compiler identification is GNU 7.3.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/tranter/git/jtranter/webinars/CMake/demo1
8

A Simple Example
% make
Scanning dependencies of target Demo1
[ 50%] Building CXX object
CMakeFiles/Demo1.dir/demo1.cpp.o
[100%] Linking CXX executable Demo1
[100%] Built target Demo1
% ./Demo1
Hello, world!
9

A Simple Example
Generated files:
CMakeCache.txt
CMakeFiles/
cmake_install.cmake
Demo1
Makefile
10

A Simple Example
Out of source build:
% cd ..
% mkdir build
% cd build
11

A Simple Example
% cmake ../demo1
-- Configuring done
-- Generating done
-- Build files have been written to: /home/tranter/git/jtranter/webinars/CMake/build
12

A Simple Example
% make
CMakeFiles/Demo1.dir/demo1.cpp.o
% ./Demo1
Hello, world!
13

A Simple Example
Using cmake-gui:
% cd demo1
% cmake-gui .
14

To add more source files:
add_executable(Demo2 demo2.cpp hello.cpp)
Or if you have many files:
add_executable(Demo2
demo2.cpp
hello.cpp
foo.cpp
bar.cpp
baz.cpp
)
15

Add a generated config file, in CMakeLists.txt:
# The version number.
set(Demo2_VERSION_MAJOR 1)
set(Demo2_VERSION_MINOR 0)
# Configure a header file to pass some of the CMake settings to source code
configure_file(
"${PROJECT_SOURCE_DIR}/config.h.in"
"${PROJECT_BINARY_DIR}/config.h"
)
# Add the binary tree to the search path for include files
# so that we will find config.h
include_directories("${PROJECT_BINARY_DIR}")
16

config.h.in:
// The configured options and settings for Demo2
#define Demo2_VERSION_MAJOR @Demo2_VERSION_MAJOR@
#define Demo2_VERSION_MINOR @Demo2_VERSION_MINOR@
17

After running cmake, generated config.h:
// The configured options and settings for Demo2
#define Demo2_VERSION_MAJOR 1
#define Demo2_VERSION_MINOR 0
18

hello.h:
void hello();
hello.cpp:
#include <iostream>
void hello()
{
std::cout << "Hello, world!" << std::endl;
}
19

demo2.cpp:
#include <iostream>
#include "hello.h"
#include "config.h"
int main()
{
std::cout << "Demo2 version " << Demo2_VERSION_MAJOR
<< "." << Demo2_VERSION_MINOR << std::endl;
hello();
return 0;
}
20

Add a shared library:
• create mathlib folder for library functions
• create mathlib/mysqrt.cpp, mathlib/mysqrt.h
mathlib/CMakeLists.txt:
# Build a library of math functions
project(mathlib)
add_library(mathlib SHARED mysqrt.cpp)
21

Additions to top level CMakeLists.txt:
# Add library to include path
include_directories("${PROJECT_SOURCE_DIR}/mathlib")
add_subdirectory(mathlib)
# Link with math library
target_link_libraries(Demo2 mathlib)
22

Additions to demo2.cpp (highlighted):
#include <iostream>
#include "hello.h"
#include "config.h"
#include "mysqrt.h"
int main()
{
std::cout << "Demo2 version " << Demo2_VERSION_MAJOR << "." << Demo2_VERSION_MINOR <<
std::endl;
hello();
for (double n = 1; n <= 10; n++) {
std::cout << "mysqrt(" << n << ") = " << mysqrt(n) << std::endl;
}
return 0;
}
23

Add support for install. Additions to CMakeLists.txt:
# Add the install targets
install(TARGETS Demo2 DESTINATION bin)
install(FILES "${PROJECT_BINARY_DIR}/config.h" DESTINATION include)
Additions to mathlib/CMakeLists.txt:
# Install targets
install(TARGETS mathlib DESTINATION lib)
install(FILES mysqrt.h DESTINATION include)
24

Building it (out of source):
% mkdir build
% cd build/
% cmake ../demo2
-- Configuring done
-- Generating done
25

% make
Scanning dependencies of target mathlib
[ 20%] Building CXX object mathlib/CMakeFiles/mathlib.dir/mysqrt.cpp.o
[ 40%] Linking CXX shared library libmathlib.so
[ 40%] Built target mathlib
[ 60%] Building CXX object CMakeFiles/Demo2.dir/demo2.cpp.o
[ 80%] Building CXX object CMakeFiles/Demo2.dir/hello.cpp.o
26

% ./Demo2
Demo2 version 1.0
Hello, world!
mysqrt(1) = 1
mysqrt(2) = 1.41421
mysqrt(3) = 1.73205
mysqrt(4) = 2
mysqrt(5) = 2.23607
mysqrt(6) = 2.44949
mysqrt(7) = 2.64575
mysqrt(8) = 2.82843
mysqrt(9) = 3
mysqrt(10) = 3.16228
27

% sudo make install
[ 40%] Built target mathlib
Install the project...
-- Install configuration: ""
-- Installing: /usr/local/bin/Demo2
-- Set runtime path of "/usr/local/bin/Demo2" to ""
-- Installing: /usr/local/include/config.h
-- Installing: /usr/local/lib/libmathlib.so
-- Installing: /usr/local/include/mysqrt.h
28

% ls
CMakeCache.txt CMakeFiles cmake_install.cmake
config.h Demo2 Makefile mathlib
% ls mathlib
CMakeFiles cmake_install.cmake libmathlib.so Makefile
29

Qt Support
• Part of standard CMake
• Requires CMake 3.1.0 or later
• Knows how to find Qt libraries
• Knows how to handle moc, UI files, resources
30

Qt Support
• CMake can find and use Qt 4 and Qt 5 libraries
• Automatically invokes moc, uic, rcc as needed
• AUTOMOC property controls automatic generation of moc
• AUTOUIC property controls automatic invocation of uic for UI files
• AUTORCC property controls automatic invocation of rcc for resource
(.qrc) files
31

Qt Example
Simple Qt Creator wizard generated application:
main.cpp mainwindow.cpp mainwindow.h mainwindow.ui
32

Qt Example
CMakeLists.txt file:
cmake_minimum_required(VERSION 3.1.0)
project(Demo3)
# Find includes in corresponding build directories
set(CMAKE_INCLUDE_CURRENT_DIR ON)
# Instruct CMake to run moc automatically when needed
set(CMAKE_AUTOMOC ON)
# Create code from a list of Qt designer ui files
set(CMAKE_AUTOUIC ON)
33

Qt Example
CMakeLists.txt file (continued):
# Find the QtWidgets library
find_package(Qt5Widgets CONFIG REQUIRED)
# Populate a CMake variable with the sources
set(demo3_SRCS
mainwindow.ui
mainwindow.cpp
main.cpp
)
# Tell CMake to create the Demo3 executable
add_executable(Demo3 WIN32 ${demo3_SRCS})
# Use the Widgets module from Qt 5
target_link_libraries(Demo3 Qt5::Widgets)
34

Qt Example
% cmake ../demo3
-- Configuring done
-- Generating done
35

Qt Example
% make
Scanning dependencies of target Demo3_autogen
[ 20%] Automatic MOC and UIC for target Demo3
[ 20%] Built target Demo3_autogen
[ 40%] Building CXX object CMakeFiles/Demo3.dir/mainwindow.cpp.o
[ 60%] Building CXX object CMakeFiles/Demo3.dir/main.cpp.o
[ 80%] Building CXX object CMakeFiles/Demo3.dir/Demo3_autogen/mocs_compilation.cpp.o
% ./Demo3
36

Qt Example
• Larger spreadsheet program
• Qt 5 port of program from C++ GUI Programming with Qt 4 book
• Widget-based, 13 source files, 2 UI files, resource file, 1300 LOC
37

Qt Example
Original qmake project file spreadsheet.pro:
lessThan(QT_MAJOR_VERSION, 5): error(This project requires Qt 5 or later)
TEMPLATE = app
QT += widgets
HEADERS = cell.h
finddialog.h
gotocelldialog.h
mainwindow.h
sortdialog.h
spreadsheet.h
SOURCES = cell.cpp
finddialog.cpp
gotocelldialog.cpp
main.cpp
mainwindow.cpp
sortdialog.cpp
spreadsheet.cpp
FORMS = gotocelldialog.ui
sortdialog.ui
RESOURCES = spreadsheet.qrc
38

Qt Example
CMakeLists.txt file:
cmake_minimum_required(VERSION 3.1.0)
project(spreadsheet)
# Find includes in corresponding build directories
set(CMAKE_INCLUDE_CURRENT_DIR ON)
# Instruct CMake to run moc automatically when needed
set(CMAKE_AUTOMOC ON)
# Create code from a list of Qt designer ui files
set(CMAKE_AUTOUIC ON)
# Automatically handle resource files
set(CMAKE_AUTORCC ON)
39

Qt Example
CMakeLists.txt file (continued):
# Find the QtWidgets library
find_package(Qt5Widgets CONFIG REQUIRED)
# Populate a CMake variable with the sources
set(spreadsheet_SRCS
cell.cpp
finddialog.cpp
gotocelldialog.cpp
main.cpp
mainwindow.cpp
sortdialog.cpp
spreadsheet.cpp
spreadsheet.qrc
)
# Tell CMake to create the spreadsheet executable
add_executable(spreadsheet WIN32 ${spreadsheet_SRCS})
# Use the Widgets module from Qt 5
target_link_libraries(spreadsheet Qt5::Widgets)
40

Qt Example
% cmake ~/git/spreadsheet/
-- Configuring done
-- Generating done
-- Build files have been written to: /home/tranter/git/jtranter/webinars/CMake/build/work
41

Qt Example
% make
Scanning dependencies of target spreadsheet_autogen
[ 8%] Automatic MOC, UIC, and RCC for target spreadsheet
[ 8%] Built target spreadsheet_autogen
[ 16%] Generating qrc_spreadsheet.cpp
Scanning dependencies of target spreadsheet
[ 25%] Building CXX object CMakeFiles/spreadsheet.dir/cell.cpp.o
[ 33%] Building CXX object CMakeFiles/spreadsheet.dir/finddialog.cpp.o
[ 41%] Building CXX object CMakeFiles/spreadsheet.dir/gotocelldialog.cpp.o
[ 50%] Building CXX object CMakeFiles/spreadsheet.dir/main.cpp.o
[ 58%] Building CXX object CMakeFiles/spreadsheet.dir/mainwindow.cpp.o
[ 66%] Building CXX object CMakeFiles/spreadsheet.dir/sortdialog.cpp.o
[ 75%] Building CXX object CMakeFiles/spreadsheet.dir/spreadsheet.cpp.o
[ 83%] Building CXX object CMakeFiles/spreadsheet.dir/qrc_spreadsheet.cpp.o
CMakeFiles/spreadsheet.dir/spreadsheet_autogen/mocs_compilation.cpp.o
[100%] Linking CXX executable spreadsheet
[100%] Built target spreadsheet
42

Localization Support
FIND_PACKAGE(Qt5LinguistTools)
# Translation files
SET(TS_FILES
spreadsheet_de.ts
spreadsheet_fr.ts
)
qt5_add_translation(QM_FILES ${TS_FILES})
# Tell CMake to create the spreadsheet executable
add_executable(spreadsheet WIN32 ${spreadsheet_SRCS} ${QM_FILES})
43

Localization Support
% cmake ../spreadsheet
...
[ 15%] Generating spreadsheet_fr.qm
Updating '/home/tranter/git/inactive/build/spreadsheet_fr.qm'...
Generated 1 translation(s) (1 finished and 0 unfinished)
Ignored 97 untranslated source text(s)
[ 23%] Generating spreadsheet_de.qm
Updating '/home/tranter/git/inactive/build/spreadsheet_de.qm'...
Generated 1 translation(s) (1 finished and 0 unfinished)
Ignored 97 untranslated source text(s)
...
% LANGUAGE=de ./spreadsheet
44

Qt Creator Support
• New project wizard can create a non-Qt C++ CMake project, but Qt-based
projects all default to qmake
• You can open an existing CMake-based project and use it
• Can edit CMake variables in project settings pane
• Keeps it's settings in a CMakeLists.txt.user file (similar to .pro.user files
with qmake)
• Make sure you enable the CMakeProjectManager plugin in Qt Creator
• Also check settings under Tools / Options... Kits/ CMake
45

Qt Creator Support
46

Qt Creator Support
47

Qt Creator Support
48

CTest
• CMake has support for defining and running unit tests
• Uses the ctest program
• See the documentation for details
49

CPack
• Support for packaging applications via the "cpack" program and
associated configuration files
• See the documentation for details
50

Misc. Tips
• For more verbose output when building: make VERBOSE=1
• Example of a sub-directories only project:
cmake_minimum_required(VERSION 3.0)
add_subdirectory(demo1)
51

Summary
• Use of CMake is increasing
• May be Qt's build system in Qt 6
• Relatively easy to use with Qt projects and Qt Creator
52

References
• https://en.wikipedia.org/wiki/CMake
• https://cmake.org/
• https://cmake.org/cmake-tutorial/
• https://cmake.org/cmake/help/latest/index.html
• https://cmake.org/download/
• https://cmake.org/cmake/help/latest/manual/cmake-qt.7.html#manual:
cmake-qt(7)
• http://doc.qt.io/qt-5/cmake-manual.html
• http://doc.qt.io/qtcreator/creator-project-cmake.html
• https://github.com/tranter/webinars/tree/master/CMake
• https://wiki.qt.io/CMake_Port
53

Q&A
• Questions?
• Any tips to share?
54

An Introduction to CMake

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