Difference between revisions of "CMake"

Revision as of 20:22, 7 May 2018

CMake is a build system which replaces automake/autoconf (the "autotools") and the shell scripts which were produced by the autotools. Similar to the autotools, the actual build on Linux is done through Makefiles. CMake supports Linux, Windows/mingw, Windows/MSVC and other platforms.

• http://www.cmake.org/Wiki/CMake_FAQ FAQ
• http://www.cmake.org/HTML/Download.html - Download
• http://www.cmake.org/HTML/Documentation.html - The same page which you also get by "man cmake".
• http://websvn.kde.org/trunk/KDE/kdelibs/cmake/modules/ - Potentially helpful additional macros
• A blog post about handling dependencies and targets for custom build commands.
• LLVM's CMake Primer, a more programmer-oriented tutorial than the one in the CMake documentation.

Building

CMake actively encourages the user to build the project in a "separate build directory". That is, if the source is located in $HOME/gnucash, you should create a new directory for where the build is located - e.g. $HOME/gnucash/build, or also $HOME/gnucash-builds/my-build.

Currently in gnucash, there is an experimental cmake build system. Hence, to build this experiment yourself, run the following commands from the top-level gnucash directory:

mkdir build-cmake
cd build-cmake
cmake ..

The general syntax here is "cmake <path to source>". Once the build directory is set up (which is the case if the build directory contains a file named CMakeCache.txt), you can re-run cmake by typing "cmake <path to build directory>", e.g.

cd build-cmake
cmake .

To run the build, as usual type

make

GnuCash Configuration Variables

GnuCash's CMakeLists.txt defines the following configuration options and defaults:

To change from a default define the option on the cmake command line, e.g. -DWITH_PYTHON=ON. Other CMake variables you may need to define:

• CMAKE_INSTALL_PREFIX: The target installation directory, defaults to /usr/local.
• CMAKE_PREFIX_PATH: A ';' separated list of paths where dependencies are installed. No default.
• GNC_DBD_DIR: The location of the dbi-driver libraries, required for the SQL backends.

FAQ

How can you change between a Debug and Release build

Use the options -DCMAKE_BUILD_TYPE=Debug or -DCMAKE_BUILD_TYPE=Release when calling CMake, or change the Variable CMAKE_BUILD_TYPE directly in the CMakeCache.txt file.

How can I see the actual compiler commands: Verbose mode?

By default, cmake builds the makefiles with verbose mode disabled. You can enable this verbose mode when calling make by the argument VERBOSE=1, like so:

make VERBOSE=1

Alternatively, you can switch on the verbose mode for the cmake configuration by setting the variable CMAKE_VERBOSE_MAKEFILE=on, like so:

cmake -DCMAKE_VERBOSE_MAKEFILE=on .

Which variables are set in CMake when running CMakeLists.txt?

That's a long list. See http://www.cmake.org/Wiki/CMake_Useful_Variables

Which C preprocessor macros tell me whether I'm on Windows or Linux?

See http://www.cmake.org/Wiki/CMake_Platform_Dependent_Issues#The_Platforms_.2F_Compilers_Table:

#ifdef __linux // For linux-only code
// ...
#ifdef _WIN32 // For Windows-MSVC and Windows-Cygwin, but *not* Windows-mingw
// ...
#ifdef __MINGW32__ // For Windows-mingw
// ...
#ifdef _MSC_VER // For only Windows-MSVC
// ...

Note: These macros do not result from CMake; instead, they exist in the respective build system already. Hence, those macros can be used regardless whether cmake is used or not.

How can I check in the CMakeLists.txt code whether I'm on Windows or Linux?

Se http://www.cmake.org/Wiki/CMake_Useful_Variables#System_.26_Compiler_Information

IF (UNIX)  # All unix-like OS's, including Apple OS X (and Cygwin)
# ...
IF (WIN32) # All windows versions (including Cygwin)
# ...
IF (MINGW) # Mingw compiler on windows
# ...
IF (MSVC)  # Microsoft compiler on windows
# ...

In other words:

• For Unix-only stuff you would write IF (UNIX)
• For Windows issues which concern either Mingw or MSVC, you would use IF (MINGW) or IF (MSVC), respectively.
• For Windows issues which hold for both compilers, you would useIF (WIN32).

Why do you use CMake at all?

See http://lists.gnucash.org/pipermail/gnucash-devel/2010-February/027582.html