Isolation of policy changes inside scripts is important for protecting
the including context. This teaches include() and find_package() to
imply a cmake_policy(PUSH) and cmake_policy(POP) around the scripts they
load, with a NO_POLICY_SCOPE option to disable the behavior. This also
creates CMake Policy CMP0011 to provide compatibility. See issue #8192.
This teaches functions and macros to use policies recorded at creation
time when they are invoked. It restores the policies as a weak policy
stack entry so that any policies set by a function escape to its caller
as before.
This re-organizes the discussion of the policy stack in documentation of
the cmake_policy() command. The new organization clearer and easier to
extend with new information.
It is likely that projects or CMake modules in the future will need to
check the value of a policy setting. For example, if we add a policy
that affects the results of FindXYZ.cmake modules, the module code will
need to be able to check the policy.
- Add a paragraph introducing the policy mechanism
- Explicitly introduce the CMP<NNNN>, OLD, and NEW notation
- Note that setting policies by CMake version is preferred
- Fix SET signature to use CMP<NNNN> notation
- Add more details about the policy stack
- Remove CMP_0001 (no slash in target name) and restore
old CMAKE_BACKWARDS_COMPATIBILITY check for it
- Replace all checks of CMAKE_BACKWARDS_COMPATIBILITY
with cmLocalGenerator::NeedBackwardsCompatibility calls
- Create new CMP_0001 to determine whether or not
CMAKE_BACKWARDS_COMPATIBILITY is used.
(old = use, new = ignore)
- Show CMAKE_BACKWARDS_COMPATIBILITY in cache only when
CMP_0001 is set to OLD or WARN
- Update documentation of cmake_policy and cmake_minimum_required
to indicate their relationship and the 2.4 version boundary
- When no cmake policy version is set in top level makefile
implicitly call cmake_policy(VERSION 2.4) which restores
CMAKE_BACKWARDS_COMPATIBILITY and other 2.4 compatibility
- Fix tests MakeClean and Preprocess to call
cmake_policy(VERSION 2.6) because they depend on new policies
Brad King
Ken Martin