There are versions out there that neither understand --version nor -V. Try a
completely different approach: execute a small python script that prints the
version number (and only that) in an easily reusable way using
sys.version_info. This is documented to work since Python 2.0. Use sys.version
for older versions, which is documented to exist since 1.5. If even that
doesn't work then simply assume we are on 1.4.0.
On dashmacmini2 the test showed output like this:
-- Found PythonInterp: /usr/bin/python (found version "Unknown option: --
usage: /usr/bin/python [option] ... [-c cmd | file | -] [arg] ...
Try `python -h' for more information.")
On my machine where python outputs "Python 2.7" this worked, but
PYTHON_VERSION_MAJOR, PYTHON_VERSION_MINOR, and PYTHON_VERSION_PATCH were all
set to "2.7".
Add some checks that the version output has the expected form before using it.
This allows the developer to tell FindPythonInterp which Python version should
be searched for. This allows the right version to be chosen for a project
without user assistance if there are specific requirements. This is especially
useful as it is common to have major versions 2 and 3 installed in parallel,
which are partly incompatible.
Using the second mode of FIND_PACKAGE_HANDLE_STANDARD_ARGS allows for
checking the version number. Now a user can require a minimum version of
the python interpreter with find_package(PythonInterp VERSION)
The old approach to determine the python executeable chooses the newest
version from _Python_VERSIONS if no additonal versions are passed.
With python it is possible to install different versions side-by-side.
Therefore a user can install e.g. python 2.5 and 2.7. Python 2.7 maybe
only installed for testing new features and 2.5 for building and running
his software. Thus the default installation for the user would be python
2.5 and then returning PYTHON_EXECUTEABLE python2.7 would be wrong. The
new approuch searches first for the the default python executable e.g.
/usr/bin/python on unix and if it can't be found _Python_VERSIONS is
used.
The FindPackageHandleStandardArgs module was originally created outside
of CMake. It was added for CMake 2.6.0 by commit e118a627 (add a macro
FIND_PACKAGE_HANDLE_STANDARD_ARGS..., 2007-07-18). However, it also
proliferated into a number of other projects that at the time required
only CMake 2.4 and thus could not depend on CMake to provide the module.
CMake's own find modules started using the module in commit b5f656e0
(use the new FIND_PACKAGE_HANDLE_STANDARD_ARGS in some of the FindXXX
modules..., 2007-07-18).
Then commit d358cf5c (add 2nd, more powerful mode to
find_package_handle_standard_args, 2010-07-29) added a new feature to
the interface of the module that was fully optional and backward
compatible with all existing users of the module. Later commit 5f183caa
(FindZLIB: use the FPHSA version mode, 2010-08-04) and others shortly
thereafter started using the new interface in CMake's own find modules.
This change was also backward compatible because it was only an
implementation detail within each module.
Unforutnately these changes introduced a problem for projects that still
have an old copy of FindPackageHandleStandardArgs in CMAKE_MODULE_PATH.
When any such project uses one of CMake's builtin find modules the line
include(FindPackageHandleStandardArgs)
loads the copy from the project which does not have the new interface!
Then the including find module tries to use the new interface with the
old module and fails.
Whether this breakage can be considered a backward incompatible change
in CMake is debatable. The situation is analagous to copying a standard
library header from one version of a compiler into a project and then
observing problems when the next version of the compiler reports errors
in its other headers that depend on its new version of the original
header. Nevertheless it is a change to CMake that causes problems for
projects that worked with previous versions.
This problem was discovered during the 2.8.3 release candidate cycle.
It is an instance of a more general problem with projects that provide
their own versions of CMake modules when other CMake modules depend on
them. At the time we resolved this instance of the problem with commit
b0118402 (Use absolute path to FindPackageHandleStandardArgs.cmake
everywhere, 2010-09-28) for the 2.8.3 release.
In order to address the more general problem we introduced policy
CMP0017 in commit db44848f (Prefer files from CMAKE_ROOT when including
from CMAKE_ROOT, 2010-11-17). That change was followed by commit
ce28737c (Remove usage of CMAKE_CURRENT_LIST_DIR now that we have
CMP0017, 2010-12-20) which reverted the original workaround in favor of
using the policy. However, existing project releases do not set the
policy behavior to NEW and therefore still exhibit the problem.
We introduced in commit a364daf1 (Allow users to specify defaults for
unset policies, 2011-01-03) an option for users to build existing
projects by adding -DCMAKE_POLICY_DEFAULT_CMP0017=NEW to the command
line. Unfortunately this solution still does not allow such projects to
build out of the box, and there is no good way to suggest the use of the
new option.
The only remaining solution to keep existing projects that exhibit this
problem building is to restore the change originally made in commit
b0118402 (Use absolute path to FindPackageHandleStandardArgs.cmake
everywhere, 2010-09-28). This also avoids policy CMP0017 warnings for
this particular instance of the problem the policy addresses.
Introduced an additional variable, Python_ADDITIONAL_VERSIONS, to both
FindPythonLibs and FindPythonInterp. Changed FindPythonInterp to loop
over versions rather than hardcoding all versions (more like libs).
This puts the new search behaviour for included files in action, i.e.
now when a file from Modules/ include()s another file, it also gets the
one from Modules/ included, i.e. the one it expects.
Alex
This adds copyright/license notification blocks CMake's find-modules.
Many of the modules had no notices at all. Some had notices referring
to the BSD license already. This commit normalizes existing notices and
adds missing notices.
FIND_PACKAGE_HANDLE_STANDARD_ARGS(), so cmake modules can specify their own
better failure messages. If the default is ok use "DEFAULT_MSG".
Do this also for FindBoost.cmake (#5349)
Alex
David Cole
Rolf Eike Beer
Björn Ricks
Brad King
Marcus D. Hanwell
Alex Neundorf
Todd Gamblin
Ken Martin
Bill Hoffman
Andy Cedilnik