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.
If the source-file form of try_compile is given a file name with
multiple '.' characters such as "a.b.c" use only the shortest extension
to check the language. This is the expected behavior and is consistent
with normal language extension determination in the method
cmSourceFileLocation::UpdateExtension.
Set CMAKE_RUNTIME_OUTPUT_DIRECTORY explicitly in try_compile projects so
that the COPY_FILE feature knows where to look. This makes the feature
robust against CMAKE_USER_MAKE_RULES_OVERRIDE files that set variables
like CMAKE_RUNTIME_OUTPUT_DIRECTORY or EXECUTABLE_OUTPUT_PATH.
This variable was introduced to help authors override CMake's default
platform information before any of it is cached. State this clearly in
the documentation. Explicitly discourage use for other purposes.
In commit 295b5b60 (Honor CMAKE_USER_MAKE_RULES_OVERRIDE in try_compile,
2010-06-29) we started passing the value of this variable when building
a try_compile project. If the variable contains a relative path it must
be treated with respect to the file where it is first used. Ensure that
the value is converted to a full path so that it is correctly referenced
in the try_compile projects.
aeb6cd8 Merge branch 'honor-explicit-zero-timeout' into resolve/mingw-cross-compile-resources/honor-explicit-zero-timeout
20d87c8 Teach Simple_Mingw_Linux2Win test to use windres
Previously this was used only in multi-configuration generators to
choose the configuration of try_compile and try_run at their build time.
Teach CMake to honor the variable in single-configuration generators as
the CMAKE_BUILD_TYPE.
Factor out generation of SccProjectName, SccLocalPath, and SccProvider
from cmLocalVisualStudio7Generator::WriteProjectStart and call it from
cmLocalVisualStudio7Generator::WriteProjectStartFortran too.
The module header was being placed in the source tree before. Thanks to
Marcel Loose for the patch, this ensures the file is written to the
build tree.
On Windows platforms source files may contain '\' in include directives:
#include "a\b.h"
Normalize these while scanning to use forward slashes. CMake will
convert from forward slashes to the direction preferred by the native
build tools when writing the path to 'depend.make' files.
Show "<variable|string>" explicitly in if() case documentation whenever
auto-dereferencing occurs. Reference its presence from the explanation
at the bottom.
The signature of get_test_property uses argument order
test property VAR
not
test VAR property
Also document the actual behavior when the property is not found.
Brad King
KWSys Robot
David Cole
Clinton Stimpson
Marcus D. Hanwell
Nicolas Despres