CMake: Detecting Platform/Operating Systems, Compiler Information

I was searching for this information from last three days. Finally I found the CMake syntax to write the platform specific code inside CMakeLists.txt.

Detecting the Operating System:

CMake actually defines several variables to identify the platform information. These variables will be assigned with the values based on the platform, operating system etc.

For example, In CMake version 2.6 following Variables are present to identify the Operating System Type.

UNIX is TRUE on all UNIX-like OS's, including Apple OS X and Cygwin.
WIN32 is TRUE on Windows, including Cygwin.
APPLE is TRUE on Apple systems.

Note: Having APPLE variable value set to TRUE does not necessarily mean that Operating System is Mac OS X. It only means that in the C/C++ header file __APPLE__ Macro is defined. Use the alternate method of detecting Operating System type, mentioned below instead.

For GNU/Linux: There is NO Variable for GNU/Linux. ie; IF(LINUX) does NOT work. Use the alternative method mentioned below instead.

Alternate method to detect to Operating System:

CMake version 2.6 defines 2 different variables, which can be used to detect the Operating System preciously.

CMAKE_SYSTEM: The complete system name, e.g. "Linux-2.4.22", "FreeBSD-5.4-RELEASE" or "Windows 5.1".
CMAKE_SYSTEM_NAME: The short system name, e.g. "Linux", "FreeBSD" or "Windows".

These variables can be used to detect the Operating System.

Example:

IF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
   # Mac OS X specific code
   SET(OperatingSystem "Mac OS X")
ENDIF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")

for detecting Mac OS X

and for Linux

IF(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
    # Linux specific code
    SET(OperatingSystem "Linux")
ENDIF(${CMAKE_SYSTEM_NAME} MATCHES "Linux")

Detecting the compiler:

Following variables can be used to detect the compilers.

Variable	Value	Meaning
MINGW	TRUE	MinGW compiler in Windows.
MSYS	TRUE	MSYS developer environment in Windows.
BORLAND	TRUE	Borland compiler in Windows.
WATCOM	TRUE	Open Watcom compiler in Windows.
MSVC, MSVC_IDE, MSVC60, MSVC70, MSVC71, MSVC80, CMAKE_COMPILER_2005, MSVC90	TRUE	Microsoft compiler.
CMAKE_COMPILER_IS_GNUCC	TRUE	compiler is a variant of GCC.
CMAKE_COMPILER_IS_GNUCXX	TRUE	compiler is a variant of g++.
CYGWIN	TRUE	Cygwin version of cmake.

Detecting the System Processor:

Following variable can be used to detect the processor family.

CMAKE_SYSTEM_PROCESSOR: the processor name (e.g. "Intel(R) Pentium(R) M processor 2.00GHz")

Example usage:

IF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
    # Mac OS X specific code
    SET(OperatingSystem "Mac OS X")

    IF(${CMAKE_SYSTEM_PROCESSOR } MATCHES "Intel")
        # Intel Mac OS X specific code
        SET(Processor "Intel")
    ENDIF(${CMAKE_SYSTEM_PROCESSOR } MATCHES "Intel")

ENDIF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")

Links:

• CMake wiki

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