7e58e5bb68
Teach CMake to prefer the system default compiler automatically when no
compiler is specified. By default use "cc" for C, "CC" for C++, and
"f95" for Fortran. Load a new Platform/<os>-<lang>.cmake module to
allow each platform to specify for each language its system compiler
name(s) and/or exclude certain names.
Create Platform/(CYGWIN|Darwin|Linux|Windows)-CXX.cmake modules to
specify "c++" as the system C++ compiler name for these platforms. On
systems that use case-insensitive filesystems exclude C++ compiler names
that are distinguished from C compiler names only by case.
This will change the default compiler selection for existing build
scripts that do not specify a compiler when run on machines with
separate system and GNU compilers both installed in the PATH. We do not
make this change in default behavior lightly. However:
(1) If a given build really needs specific compilers one should specify
them explicitly e.g. by setting CC, CXX, and FC in the environment.
(2) The motivating case is to prefer the system Clang on newer OS X
systems over the older GNU compilers typically also installed. On
such systems the names "cc" and "c++" link to Clang. This is the
first platform known to CMake on which "c++" is not a GNU compiler.
The old behavior selected "gcc" for C and "c++" C++ and therefore
chooses GNU for C and Clang for C++ by default. The new behavior
selects GNU or Clang consistently for both languages on older or
newer OS X systems, respectively.
(3) Other than the motivating OS X case the conditions under which the
behavior changes do not tend to exist in default OS installations.
They typically occur only on non-GNU systems with manually-installed
GNU compilers.
(4) The consequences of the new behavior are not dire. At worst the
project fails to compile with the system compiler when it previously
worked with the non-system GNU compiler. Such failure is easy to
work around (see #1).
In short this change creates a more sensible default behavior everywhere
and fixes poor default behavior on a widely-used platform at the cost of
a modest change in behavior in less-common conditions.
This is CMake, the cross-platform, open-source make system. CMake is distributed under the BSD License, see Copyright.txt. For documentation see the Docs/ directory once you have built CMake or visit http://www.cmake.org. Building CMake ============== Supported Platforms ------------------- MS Windows, Mac OS X, Linux, FreeBSD, Solaris, HP-UX, IRIX, BeOS, QNX Other UNIX-like operating systems may work too out of the box, if not it shouldn't be a major problem to port CMake to this platform. Contact the CMake mailing list in this case: http://www.cmake.org/mailman/listinfo/cmake If you don't have any previous version of CMake already installed -------------------------------------------------------------- * UNIX/Mac OSX/MinGW/MSYS/Cygwin: You need to have a compiler and a make installed. Run the bootstrap script you find the in the source directory of CMake. You can use the --help option to see the supported options. You may want to use the --prefix=<install_prefix> option to specify a custom installation directory for CMake. You can run the bootstrap script from within the CMake source directory or any other build directory of your choice. Once this has finished successfully, run make and make install. So basically it's the same as you may be used to from autotools-based projects: $ ./bootstrap; make; make install * Other Windows: You need to download and install a binary release of CMake in order to build CMake. You can get these releases from http://www.cmake.org/HTML/Download.html . Then proceed with the instructions below. You already have a version of CMake installed --------------------------------------------- You can build CMake as any other project with a CMake-based build system: run the installed CMake on the sources of this CMake with your preferred options and generators. Then build it and install it. For instructions how to do this, see http://www.cmake.org/HTML/RunningCMake.html