Ubuntu 20.04 is a supported platform and comes with CMake 3.16. The
current state of the Qt build works fine with this CMake version, mainly
because the default build on Linux is single-config.
For multi-config builds we have higher version requirements as
documented in cmake/README.md.
This lowers the barrier for users using single-config builds who don't
want or cannot upgrade to CMake >= 3.18.
For Ninja Multi-Config builds, which were introduced by CMake 3.17, we
yield a warning that 3.18.3 is the lowest supported version.
Pick-to: 6.0
Change-Id: Ia918b9f2b494508e86301ffc0e138d3ad4dbaf86
Reviewed-by: Craig Scott <craig.scott@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
When a CMake release introduces a new policy that affects most Qt
modules, it may be appropriate to make each module aware of that newer
CMake version and use the NEW policy without raising the minimum CMake
version requirement. To reduce the churn associated with making that
change across all Qt modules individually, this change allows it to be
updated in a central place (qtbase), but in a way that allows a Qt
module to override it in its own .cmake.conf file if required (e.g. to
address the issues identified by policy warnings at a later time). The
policies are modified at the start of the call to
qt_build_repo_begin().
For commands defined by the qtbase module, qtbase needs to be in
control of the policy settings at the point where those commands are
defined. The above mechanism should not affect the policy settings for
these commands, so the various *Config.cmake.in files must not specify
policy ranges in a way that a Qt module's .cmake.conf file could
influence.
Starting with CMake 3.12, policies can be specified as a version range
with the cmake_minimum_required() and cmake_policy() commands. All
policies introduced in CMake versions up to the upper limit of that
range will be set to NEW. The actual version of CMake being used only
has to be at least the lower limit of the specified version range.
This change uses cmake_minimum_required() rather than cmake_policy()
due to the latter not halting further processing upon failure.
See the following:
https://gitlab.kitware.com/cmake/cmake/-/issues/21557
Task-number: QTBUG-88700
Pick-to: 6.0
Change-Id: I0a1f2611dd629f847a18186394f500d7f52753bc
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Add a new function that returns the minimum CMake version required to
build Qt. Pass that value to cmake_minimum_required() when building
qtbase and its standalone tests.
The minimum supported CMake version is read from qtbase/.cmake.conf
and its value should be updated when the need arises. It's the main
source of truth for all repos.
Provide a way to lower the minimum CMake version at configure time by
passing a value via QT_FORCE_MIN_CMAKE_VERSION.
This is not an officially supported way of building Qt. If the
specified version is lower than Qt's supported minimum, show a
warning.
Nevertheless the option is useful for testing how Qt builds with a
different minimum CMake version due to different policies being
enabled by default.
Issue warnings for CMake versions that are higher than the minimum
version but are known to cause issues when building Qt.
A counterpart change is needed in qt5 to ensure the minimum CMake
version is set at the proper time for top-level builds.
Ideally we would use the same 'check the CMake minimum version` code
in all our repositories, but that will cause lots of duplication because
we can't really find_package() the code and doing something like
include(../qtbase/foo.cmake) hardcodes assumptions about repo
locations.
So for now we don't bump the minimum version in child repo
cmake_minimum_required calls (qtsvg, qtdeclarative, etc).
Instead we record both the minimum supported version and the computed
minimum version (in case a different version was forced) in
QtBuildInternalsExtra.cmake.
Then we require qtbase's computed min version in
qt_build_repo_begin().
This won't set policies as cmake_minimum_required would, but at least
it propagates what minimum CMake version should be used for child
repos.
We might still have to bump the versions in child repos at some point.
Task-number: QTBUG-88086
Change-Id: Ida1c0d5d3e0fbb15d2aee9b68abab7a1648774b9
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
And create one for QtBase at the same time.
Fixes: QTBUG-83835
Change-Id: Icc6b022165a57bd4e22c23bdb0016522b99a5b80
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
