CMake Useful Variables: Difference between revisions

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; CMAKE_VERBOSE_MAKEFILE : set this to true if you are using makefiles and want to see the full compile and link commands instead of only the shortened ones
; CMAKE_VERBOSE_MAKEFILE : set this to true if you are using makefiles and want to see the full compile and link commands instead of only the shortened ones
; CMAKE_SKIP_INSTALL_ALL_DEPENDENCY : since CMake 2.1 the install rule depends on all, i.e. everything will be built before installing. If you don't like this, set this one to true.
; CMAKE_SKIP_INSTALL_ALL_DEPENDENCY : since CMake 2.1 the install rule depends on all, i.e. everything will be built before installing. If you don't like this, set this one to true.
; CMAKE_SUPPRESS_REGENERATION : this will cause CMake to not put in the rules that re-run CMake. This might be useful if you  want to use the generated build files on another machine.


== Compilers and Tools ==
== Compilers and Tools ==

Revision as of 16:06, 12 May 2005

CMake uses and defines several variables, which can be used in CMakeLists.txt files.

Locations

CMAKE_SOURCE_DIR
this is the directory, from which cmake was started, i.e. the top level source directory
CMAKE_CURRENT_SOURCE_DIR
this is the directory where the currently processed CMakeLists.txt is located in
CMAKE_BINARY_DIR
if you are building in-source, this is the same as CMAKE_SOURCE_DIR, otherwise this is the top level directory of your build tree
CMAKE_CURRENT_BINARY_DIR
if you are building in-source, this is the same as CMAKE_CURRENT_SOURCE_DIR, otherwise this is the directory where the compiled or generated files from the current CMakeLists.txt will go to
CMAKE_ROOT
this is the CMake installation directory

Various Options

CMAKE_SKIP_RULE_DEPENDENCY
set this to true if you don't want to rebuild the object files if the rules have changed, but not the actual source files or headers (e.g. if you changed the some compiler switches)
CMAKE_VERBOSE_MAKEFILE
set this to true if you are using makefiles and want to see the full compile and link commands instead of only the shortened ones
CMAKE_SKIP_INSTALL_ALL_DEPENDENCY
since CMake 2.1 the install rule depends on all, i.e. everything will be built before installing. If you don't like this, set this one to true.
CMAKE_SUPPRESS_REGENERATION
this will cause CMake to not put in the rules that re-run CMake. This might be useful if you want to use the generated build files on another machine.

Compilers and Tools

A simple way to get switches to the compiler is to use ADD_DEFINITIONS(). But there are also two variables exactly for this purpose:

CMAKE_C_FLAGS
the compiler flags for compiling C sources
CMAKE_CXX_FLAGS
the compiler flags for compiling C++ sources

The following variables are detected during the cmake run and set accordingly (e.g. to gcc). If you want to force the use of other tools, you can set these variables manually to the desired tools. E.g. if you want to use the gcc cross compiling toolchain for arm processors, you could do the following: SET(CMAKE_C_COMPILER arm-elf-gcc)

CMAKE_C_COMPILER
the compiler used for C files
CMAKE_CXX_COMPILER
the compiler used for C++ files
CMAKE_COMPILER_IS_GNUCC
if the compiler is a variant of gcc, this should be set to 1
CMAKE_COMPILER_IS_GNUCXX
if the compiler is a variant of g++, this should be set to 1
CMAKE_AR, CMAKE_RANLIB
the tools for creating libraries

Build rules

Build rules are defined in CMakeCInformation.cmake and CMakeCXXInformation.cmake.

Rules for C++ sources:

  • CMAKE_CXX_CREATE_SHARED_LIBRARY
  • CMAKE_CXX_CREATE_SHARED_MODULE
  • CMAKE_CXX_CREATE_STATIC_LIBRARY
  • CMAKE_CXX_COMPILE_OBJECT
  • CMAKE_CXX_LINK_EXECUTABLE

and the equivalents for C sources:

  • CMAKE_C_CREATE_SHARED_LIBRARY
  • CMAKE_C_CREATE_SHARED_MODULE
  • CMAKE_C_CREATE_STATIC_LIBRARY
  • CMAKE_C_COMPILE_OBJECT
  • CMAKE_C_LINK_EXECUTABLE

You can override the variables manually, e.g. replacing some flags in the linker command, but you can't change the value of the variables in sharp braces. Usually you don't have to change these rules, only in rare cases. You should only do this if you know what you are doing and there is no other way.