How to create a shared library with cmake

Question

I have written a library that I used to compile using a self-written Makefile  but now I want to switch to cmake  The tree looks like this  I removed all the irrelevant files       -- include         -- animation h         -- buffers h         --             -- vertex h         -- world h  -- src      -- animation cpp      -- buffers cpp      --          -- vertex cpp      -- world cpp   So what I am trying to do is just to compile the source into a shared library and then install it with the header files   Most examples that I have found compile executables with some shared libraries but never just a plain shared library  It would also be helpful if someone could just tell me a very simple library that uses cmake  so I can use this as an example

User · Answer

I m trying to learn how to do this myself  and it seems you can install the library like this   cmake minimum required VERSION 2 4 0   project mycustomlib     Find source files file GLOB SOURCES src   cpp     Include header files include directories include     Create shared library add library   PROJECT NAME  SHARED   SOURCES      Install library install TARGETS   PROJECT NAME  DESTINATION lib   PROJECT NAME      Install library headers file GLOB HEADERS include   h  install FILES   HEADERS  DESTINATION include   PROJECT NAME

User · Answer

This minimal CMakeLists txt file compiles a simple shared library   cmake minimum required VERSION 2 8   project  test  set CMAKE BUILD TYPE Release   include directories   CMAKE CURRENT SOURCE DIR  include  add library test SHARED src test cpp    However  I have no experience copying files to a different destination with CMake  The file command with the COPY INSTALL signature looks like it might be useful

User · Answer

Always specify the minimum required version of cmake  cmake minimum required VERSION 3 9    You should declare a project  cmake says it is mandatory and it will define convenient variables PROJECT NAME  PROJECT VERSION and PROJECT DESCRIPTION  this latter variable necessitate cmake 3 9    project mylib VERSION 1 0 1 DESCRIPTION  mylib description     Declare a new library target  Please avoid the use of file GLOB       This feature does not provide attended mastery of the compilation process  If you are lazy  copy-paste output of ls -1 sources   cpp    add library mylib SHARED     sources animation cpp     sources buffers cpp               Set VERSION property  optional but it is a good practice    set target properties mylib PROPERTIES VERSION   PROJECT VERSION     You can also set SOVERSION to a major number of VERSION  So libmylib so 1 will be a symlink to libmylib so 1 0 0   set target properties mylib PROPERTIES SOVERSION 1    Declare public API of your library  This API will be installed for the third-party application  It is a good practice to isolate it in your project tree  like placing it include  directory   Notice that  private headers should not be installed and I strongly suggest to place them with the source files   set target properties mylib PROPERTIES PUBLIC HEADER include mylib h    If you work with subdirectories  it is not very convenient to include relative paths like     include mylib h   So  pass a top directory in included directories   target include directories mylib PRIVATE      or  target include directories mylib PRIVATE include  target include directories mylib PRIVATE src    Create an install rule for your library  I suggest to use variables CMAKE INSTALL  DIR defined in GNUInstallDirs   include GNUInstallDirs    And declare files to install   install TARGETS mylib     LIBRARY DESTINATION   CMAKE INSTALL LIBDIR      PUBLIC HEADER DESTINATION   CMAKE INSTALL INCLUDEDIR     You may also export a pkg-config file  This file allows a third-party application to easily import your library    with Makefile  see pkg-config with Autotools  see PKG CHECK MODULES with cmake  see pkg check modules   Create a template file named mylib pc in  see pc 5  manpage  for more information    prefix  CMAKE INSTALL PREFIX  exec prefix  CMAKE INSTALL PREFIX  libdir   exec prefix   CMAKE INSTALL LIBDIR  includedir   prefix   CMAKE INSTALL INCLUDEDIR   Name   PROJECT NAME  Description   PROJECT DESCRIPTION  Version   PROJECT VERSION   Requires  Libs  -L  libdir  -lmylib Cflags  -I  includedir    In your CMakeLists txt  add a rule to expand   macros   ONLY ask to cmake to not expand variables of the form   VAR     configure file mylib pc in mylib pc  ONLY    And finally  install generated file   install FILES   CMAKE BINARY DIR  mylib pc DESTINATION   CMAKE INSTALL DATAROOTDIR  pkgconfig    You may also use cmake EXPORT feature  However  this feature is only compatible with cmake and I find it difficult to use   Finally the entire CMakeLists txt should looks like   cmake minimum required VERSION 3 9  project mylib VERSION 1 0 1 DESCRIPTION  mylib description   include GNUInstallDirs  add library mylib SHARED src mylib c  set target properties mylib PROPERTIES     VERSION   PROJECT VERSION      SOVERSION 1     PUBLIC HEADER api mylib h  configure file mylib pc in mylib pc  ONLY  target include directories mylib PRIVATE    install TARGETS mylib     LIBRARY DESTINATION   CMAKE INSTALL LIBDIR      PUBLIC HEADER DESTINATION   CMAKE INSTALL INCLUDEDIR   install FILES   CMAKE BINARY DIR  mylib pc     DESTINATION   CMAKE INSTALL DATAROOTDIR  pkgconfig

User · Answer

First  this is the directory layout that I am using      -- include       -- class1 hpp       --           -- class2 hpp  -- src      -- class1 cpp      --          -- class2 cpp   After a couple of days taking a look into this  this is my favourite way of doing this thanks to modern CMake   cmake minimum required VERSION 3 5  project mylib VERSION 1 0 0 LANGUAGES CXX   set DEFAULT BUILD TYPE  Release    if NOT CMAKE BUILD TYPE AND NOT CMAKE CONFIGURATION TYPES    message STATUS  Setting build type to    DEFAULT BUILD TYPE   as none was specified      set CMAKE BUILD TYPE    DEFAULT BUILD TYPE   CACHE STRING  Choose the type of build   FORCE      Set the possible values of build type for cmake-gui   set property CACHE CMAKE BUILD TYPE PROPERTY STRINGS  Debug   Release   MinSizeRel   RelWithDebInfo   endif    include GNUInstallDirs   set SOURCE FILES src class1 cpp src class2 cpp   add library   PROJECT NAME        target include directories   PROJECT NAME  PUBLIC       lt BUILD INTERFACE   CMAKE CURRENT SOURCE DIR  include gt        lt INSTALL INTERFACE include gt      PRIVATE src   set target properties   PROJECT NAME  PROPERTIES     VERSION   PROJECT VERSION      SOVERSION 1   install TARGETS   PROJECT NAME  EXPORT MyLibConfig     ARCHIVE  DESTINATION   CMAKE INSTALL LIBDIR      LIBRARY  DESTINATION   CMAKE INSTALL LIBDIR      RUNTIME  DESTINATION   CMAKE INSTALL BINDIR   install DIRECTORY include  DESTINATION   CMAKE INSTALL INCLUDEDIR    PROJECT NAME    install EXPORT MyLibConfig DESTINATION share MyLib cmake   export TARGETS   PROJECT NAME  FILE MyLibConfig cmake    After running CMake and installing the library  there is no need to use Find    cmake files  it can be used like this   find package MyLib REQUIRED    No need to perform include directories      target link libraries   TARGET  mylib    That s it  if it has been installed in a standard directory it will be found and there is no need to do anything else  If it has been installed in a non-standard path  it is also easy  just tell CMake where to find MyLibConfig cmake using   cmake -DMyLib DIR  non standard install path      I hope this helps everybody as much as it has helped me  Old ways of doing this were quite cumbersome

[c++] How to create a shared library with cmake?

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