Backstory.
The main reason why we keep getting "unable to promote 3rd party 'X'
target to global scope" errors when building Qt repositories, is
because we try to promote 3rd party imported targets in a different
scope than where the imported targets were created.
What were the main motivations for promoting 3rd party targets to
global?
1) imported targets are by default local to the directory scope they
were created in
2) we want 3rd party targets to be accessible across subdirectory
scopes, but looked up once, e.g. qt_find_package(JPEG) looked up in
src/gui/CMakeLists.txt, but the target should also be usable in the
sibling scope
src/plugins/imageformats/CMakeLists.txt
Having the package lookup close to the consuming qt module is easier
to maintain, because all the other 3rd party dependency lookups are
in the same file. This goes against the conventional CMake advice
where each subdirectory should look for its own dependencies, or the
dependency should be available directly in the root project scope.
3) to make the 3rd party targets available in the root project scope
as part of the following flow:
QtPostProcess.cmake ->
qt_internal_create_module_depends_file() ->
qt_collect_third_party_deps() ->
get_property(INTERFACE_QT_PACKAGE_NAME) ->
write 3rd party Dependencies.cmake file for each qt module.
Properties can only be queried from an imported target if it's in
the same scope or was promoted to global, otherwise you get
'non-existent target' errors.
4) for prl and pri file generation, where we need the targets to be
available during generator expression evaluation within the
relevant qt module directory scope
Here is a list of approaches I came up with on how to improve the
situation.
1) Make all imported targets global during the Qt build, by iterating
over the directory property IMPORTED_TARGETS and making each one
global.
Requires CMake 3.21.
Status: Already implemented for a long time, but is opt-in.
Pros: Relatively robust
Cons: Minimum CMake version for building Qt is 3.16.
2) Make all imported targets global during the Qt build using the
CMAKE_FIND_PACKAGE_TARGETS_GLOBAL variable.
Requires CMake 3.24.
Status: Not implemented, but can be set by Qt builders directly on
the command line.
Pros: Should be robust
Cons: Minimum CMake version for building Qt is 3.16.
3) Abandon the desire to have a single qt_find_package in a single
directory scope, and embrace the CMake-way of repeating the
dependency in each subdirectory that requires it.
Status: Not implemented.
Pros: Should be robust
Cons: A lot of qt_find_package duplication, will require rewriting
various code paths, QtPostProcess would have to be done at
directory scope, unclear if dependency tracking will still work
work reliably when there might be multiple same-named
directory-scoped targets, other unknown unknowns
4) Move all qt_find_package calls into a $repo_name/dependencies.cmake
file which would be read at project root scope. This would
potentially avoid all scoping issues, because all dependencies will
have to be specified at root scope.
Status: Not implemented.
Pros: No duplication
Cons: Dependencies are not scoped anymore to module directories,
won't be able to conditionally look for dependencies based on
module feature evaluation, not clear yet how this will tie into
standalone tests which are in tests/ subdir, other unknown unknowns
5) Try to promote as many 3rd party libraries at project root scope
as possible.
Currently we have 2 general locations where we look up
dependencies.
One is each qt_find_package call. The other is
Qt6FooDependencies.cmake ->
_qt_internal_find_third_party_dependencies().
Many 3rd party targets are created by
_qt_internal_find_third_party_dependencies() in the root scope, but
not promoted, and then we try to promote them in child scopes using
qt_find_package, which causes the promotion errors.
Starting with 58eefbd0b6169d0749b312268c1ae1e594e04362 and
37a5e001277db9e1392a242171ab2b88cb6c3049 we now record the provided
targets of previous qt_find_package calls.
So instead of waiting to try and promote targets later during the
configuration process, we can make sure we promote the targets at
_qt_internal_find_third_party_dependencies() call time, right
when we lookup the Qt dependencies of the qt repo, in the root
scope.
Status: Implemented in this change
Notably, we only promote 3rd party targets to global for qt builds,
and not user projects, to not accidentally break user project
behaviors.
Also, we only promote 3rd party targets, and not Qt internal
targets like Qt6::Core, Qt6::Platform, Qt6::PlatformCommonInternal,
Qt6::GlobalConfig, etc, for a few reasons:
- the code that requires targets to be global only cares about
3rd party targets
- promoting the internal targets is more prone to breaking, because
there is more than one place where find_package(Qt6Foo) might be
called, and if that ends up being in a different directory scope,
we encounter the same global promotion errors.
Some notable cases where this happens:
- tests/CMakeLists.txt brings in extra Qt packages via
StandaloneTestsConfig.cmake files
- qtbase standalone tests qt_internal_qtbase_pre_project_setup()
calls find_package(Qt6 COMPONENTS BuildInternals) which ends
up creating the Platform target in the root scope instead of
the tests/ scope
- Qt6::BundledLibpng links against Core, which ends up trying to
promote Core's internal dependencies Platform and GlobalConfig
To only promote 3rd party targets, we walk the dependencies of
an initial target recursively, and skip promoting targets that have
the _qt_is_internal_target or
_qt_should_skip_global_promotion_always properties set.
Pros: Improves the situation compared to the status quo
Cons: Still not ideal due to the various filtering of internal
targets and having to mark them as such.
6) Avoid promoting targets to global if we can detect that the target
was created in a different scope than where we are trying to
promote it.
We can do that by comparing the target's BINARY_DIR to the
CMAKE_CURRENT_BINARY_DIR and skip promotion if they are not equal.
Status: Not implemented, but we can consider it because it's
quick to do.
Pros: More robust than newly implemented approach (5)
Cons: Requires CMake 3.18, because trying to read the BINARY_DIR
property on an INTERFACE_LIBRARY would error out.
Also, if we implement it and make it the default when using 3.18+,
we might 'collect' a lot more hidden promotion errors that will
only be revealed later once someone uses CMake 3.16 or 3.17,
because most will probably use newer CMake versions.
Perhaps the trade-off is worth it?
Fixes: QTBUG-89204
Fixes: QTBUG-94356
Fixes: QTBUG-95052
Fixes: QTBUG-98807
Fixes: QTBUG-125371
Change-Id: I088a17a98ef35aa69537a3ad208c61de40def581
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
(cherry picked from commit d2e85cede01c0898ca73cbc3fb9f53aa9612cab5)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
They will used from another Public.cmake file in a follow up commit.
Change-Id: I71b69ed76ca48c391ba45329eb9c305e4a2a238b
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
(cherry picked from commit dad49f5a1e91dbdf91a683e0a68d05cdfa2e1ef1)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
To ensure examples can be built as ExternalProjects, the example
subdirectories need to be added via qt_internal_add_example rather
than just add_subdirectory.
qt_internal_add_example is also needed for correct installation of
example sources.
To catch examples that are still not added via
qt_internal_add_example, set a QT_WARN_ABOUT_EXAMPLE_ADD_SUBDIRECTORY
variable at the top of the examples/CMakeLists.txt directory scope
and show a warning in qt_add_executable whenever that variable is
TRUE.
Calls of qt_internal_add_example will set the variable to FALSE,
making sure the warning is not shown for properly added examples.
This is limited to developer builds and can be opted out of via the
QT_NO_WARN_ABOUT_EXAMPLE_ADD_SUBDIRECTORY_WARNING variable.
qt_add_executable is used as the 'hook' for showing the error, because
that is the most likely function to be used in examples.
We don't use qt_standard_project_setup in all projects yet, so we
don't want to use that one.
Task-number: QTBUG-90820
Task-number: QTBUG-123096
Change-Id: I7a0b0b2cc60c70903db03b56c06494c127a62420
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
When using MinGW compiler and Qt is configured with "-static-runtime",
we should pass "-static" to g++ while linking, like Qt 5, instead of
"-Wl,-Bstatic", to get rid of dependencies on libgcc_s_seh-1.dll,
libwinpthread-1.dll and libstdc++-6.dll.
Because syncqt doesn't link to any Qt library,
"target_link_options(${target} INTERFACE -static)" has no effect on it.
So we should use "PRIVATE" instead of "INTERFACE" for executables.
Pick-to: 6.6 6.5
Change-Id: Icf551783f92ef3615b3840c9af16d163eee09fdb
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
CMakeLists.txt and .cmake files of significant size
(more than 2 lines according to our check in tst_license.pl)
now have the copyright and license header.
Existing copyright statements remain intact
Task-number: QTBUG-88621
Change-Id: I3b98cdc55ead806ec81ce09af9271f9b95af97fa
Reviewed-by: Jörg Bornemann <joerg.bornemann@qt.io>
These TODOs were left as a marker to be checked once the official
CMake 3.21.0 release was made. The things they refer to were included
in the CMake 3.21.0 release, so the TODOs can be removed.
Fixes: QTBUG-94528
Pick-to: 6.2
Change-Id: I769605de85df657ad056123e787ec9849b77e42f
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
The -static argument we used before is supported by ld, but not lld.
The latter requires --static or -Bstatic. Use -Bstatic, which is
supported by both.
Pick-to: 6.2
Fixes: QTBUG-89549
Change-Id: I3c3069661bf4cd20e3298aff4714163b7419d3ef
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
If Qt was configured with -static-runtime which implies MultiThreaded
-MT flag, the plugin initializer object libraries were still compiled
with the default -MD flag.
When an application linked to Qt, that caused linking to fail with
mismatched symbol errors between the application symbols and the
plugin initializer object library symbols.
Make sure to set the MSVC_RUNTIME_LIBRARY property on both plugin
initializer and resource object libraries, depending on the value of
QT_FEATURE_static_runtime.
We did set the property for resources added by
qt_internal_add_resource, but not for the resource created by
the public qt6_add_resources counterpart.
Pick-to: 6.2
Fixes: QTBUG-95043
Change-Id: Ia543cd0241db94a12080be2655ad420fe9ad3f24
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
target_link_options are placed by CMake at the beginning of a linker
line. This gives us an opportunity to use the function to propagate
object libraries. This change adds one more check in the root
Config.cmake file. If CMP0099 policy is enabled, CMake enables
propagating of the linking options when linking two static libraries
using the PRIVATE linking visibility, so we can rely on the correct
linking order and expect object libraries to be propagated.
Note that on the platforms where cmake version is higher than 3.16
Qt uses CMP0099 NEW in functions like qt_add_executable. This means
that at the moment of creating an executable target the TARGET_POLICY
genex will also be NEW, so we do not take into the account the user
defined CMP0099.
If the CMP0099 policy is not available for a certain CMake version
we skip the TARGET_POLICY check and simply disable propagation of
the object libraries using target_link_options for both user and Qt
libraries. This is applicable for the CMake versions 3.16 and less.
Linking approaches have the following priorities(from higher to lower)
after this change:
- target_link_libraries - works if link order matters not or CMake
version greater equal 3.21.
- target_link_options - works if CMP0099 is set to NEW by user or
if the CMake version is greater than or equal to 3.17 and an
executable is created using Qt functions.
- object library finalizer - works if CMake version is greater equal
3.19 or qt6_finalize_target is called explicitly.
- target_sources - is used when all the other approaches could not
be used.
Amends a1fd4f51ada82854f35654158a334454e760a9f7
Amends 3329212815777e33dfb4697b748d10927d73f44c
Pick-to: 6.2
Change-Id: I14f88caeb04e357191c840abeab89b03e210b796
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Ensure that the finalizer approach of
__qt_internal_propagate_object_library considers $<LINK_ONLY:>
libraries when traversing the dependencies of a target.
The issue was discovered when using the Quick.Shapes QML module in a
static build. The module has both a backing library and a plugin.
The backing library has some resource objects associated with it.
When the targets are exported, the plugin INTERFACE_LINK_LIBRARIES
has a $<LINK_ONLY:QuickShapes> dependency.
This ensures that the library will be linked, but depending on which
linking approach in __qt_internal_propagate_object_library is used,
the resources might not be linked to the final executable.
The resources are linked correctly when using the
target_link_libraries approach, but not when using the finalizer or
target_sources approach.
This change fixes the finalizer approach, but the target_sources
approach is still broken.
Amends a1fd4f51ada82854f35654158a334454e760a9f7
Pick-to: 6.2
Change-Id: Ifbb91a17d388c3dc4263e17ec0d3bd5627b57cb4
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Check if link order matters before use the object library finalizer.
Amends 5fb99e3860eb43f4bacacec7f4a4626cb0159b14
Pick-to: 6.2
Change-Id: Ie996bc175ebea36ccda1bb2fe388ae3b7fcde395
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
The linking logic of object libraries should be reusable outside of the
resource context. This introduces a
__qt_internal_propagate_object_library function that prepares all the
necessary genexes to link and propagate the object library to the
end-point executable.
Rename resource object finalizer API to make the naming more generic
to object libraries of any kind.
Amends 5fb99e3860eb43f4bacacec7f4a4626cb0159b14
Pick-to: 6.2
Task-number: QTBUG-93002
Task-number: QTBUG-94528
Change-Id: I69d0f34c0dadbd67232de91035aaa53af93d1fa1
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Remove target specific flags from static_link_order.
Move the check to the common config.tests folder.
Amends 5fb99e3860eb43f4bacacec7f4a4626cb0159b14
Pick-to: 6.2
Task-number: QTBUG-93002
Task-number: QTBUG-94528
Change-Id: I1368075ec6bd1e743b2b89fd93143df38a278ec2
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
For user projects we run the static link order check once
'find_package(Qt6 ...)' is called.
If linker can resolve circular dependencies between static libraries
and object files we set the _qt_link_order_matters property of the
Qt::Platform target. This indicates the use of finalizers is not
required and we may rely on CMake-base propagation of resource
libraries and resource object files.
If linker could not resolve circular dependencies depending on
the _qt_resource_objects_finalizer_mode value:
- Finalizer will be called and collected resource objects will be
linked to the target directly.
- Finalizer will be omitted and resource objects will be linked
using the target_sources function implicitly. This only
propagates resource one level up if consumer links the static
library PUBLICly, but all symbols will be resolved correctly
since object files are placed in the beginning of the linker line.
In the CMake version 3.21 we expect that CMake will take care about
the order of the resource object files in a linker line, it's
expected that all object files are located at the beginning of the
linker line.
TODO: Need to confirm that the CMake 3.21 meets the expectations.
Amends 4e901a2f99cbfda3b479253ea54b16f02e1c3aa5
Pick-to: 6.2
Task-number: QTBUG-93002
Task-number: QTBUG-94528
Change-Id: Ia68976df8182d3d3007b90c475c1e3928a305339
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
CMake 3.21 introduced a new IMPORTED_TARGETS directory property which
we can use to promote all imported targets within a scope to be
global.
This would cover transitive non-Qt imported targets which the Qt build
system does not know about and is thus a more complete solution
compared to promoting only Qt targets.
Run a finalizer at the end of the directory scope where
find_package(Qt6) is called to promote all imported targets within
that scope to global (when requested).
The old promotion method is disabled when the CMake version is new
enough.
Pick-to: 6.2
Task-number: QTBUG-92878
Task-number: QTBUG-94528
Change-Id: I533a3bd4186eba652f878ddd72c76118c2fd8bae
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
User projects can set the QT_PROMOTE_TO_GLOBAL_TARGETS variable to
true so that the various imported targets created by find_package(Qt6)
are promoted to global targets.
This would allow a project to find Qt packages in a subdirectory scope
while using those Qt targets from a different scope.
E.g. it fixes errors like
CMake Error at CMakeLists.txt:5 (target_link_libraries):
Error evaluating generator expression:
$<TARGET_OBJECTS:Qt6::Widgets_resources_1>
Objects of target "Qt6::Widgets_resources_1" referenced but no such
target exists.
when trying to use a static Qt from a sibling scope.
Various 3rd party dependency targets (like Atomic or ZLIB) are not
made global due to limitations in CMake, but as long as those targets
are not mentioned directly, it shouldn't cause issues.
The targets are made global in the generated
QtFooAdditionalTargetInfo.cmake file.
To ensure that resource object libraries promoted, the generation
of the file has to be done at the end of the defining scope
where qt_internal_export_additional_targets_file is called,
which is achieved with a deferred finalizer.
Replaced all occurrences of target promotion with a helper function
which allows tracing of all promoted targets by specifying
--log-level=debug to CMake.
Pick-to: 6.2
Fixes: QTBUG-92878
Change-Id: Ic4ec03b0bc383d7e591a58c520c3974fbea746d2
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
Resource objects might be linked to plugins. Since some plugins may
be present in LINK_LIBRARIES as the complex genexes, need to collect
them explicitly and iterate over plugin targets to find resource object
libraries that need to be exposed to end-point target executable.
Amends a1fd4f51ada82854f35654158a334454e760a9f7
Change-Id: Icd85f54f7bf9d1b7e3382caa5d9aa62449b6adb8
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Avoid getting the LINK_LIBRARY property of the interface libraries
when calling a resource object finalizer.
Amends a1fd4f51ada82854f35654158a334454e760a9f7
Change-Id: I19d625a927c66994902f5c89e6c82183c94af91e
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
In the previous implementation of the resource object finalizer, we
used the name of the resource object library without namespaces when
recording it in the resource libraries list. This causes an issue when
we or users export resource targets.
This approach marks resource object libraries with the exporting
property instead of collecting resource targets when creating them.
Amends 19e789bace887105badae83c0a79429bbf8e8221
Change-Id: I8596815921f2c681ddd78d9b2e9a4e1cafe5000b
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
This proposal collects all the resource objects to the qt-specific
property of the static libraries. This is done to avoid littering
of other static libraries and put resource object files to the
source part of the linker line when linking the end-point
executable.
The way we link object resource libraries is changed back to the
target_link_libraries approach as we may omit using finalizers
with linkers other than ld. Users may enforce finalizers by calling
the qt6_enable_resource_objects_finalizer_mode function if need.
Refactor tests related to the static resources.
Amends ddaa7150d85624ab545ccfe098fe8b2d18241940
Task-number: QTBUG-93002
Change-Id: I74135e291cd82fb54d1b284b4b4a1e002b1fef98
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Needed for the upcoming static plugin mechanism, where we have to
extract the list of Qt module dependencies of a target and then extract
the plugins associated with those modules.
To do that we need to recursively collect the dependencies of a given
target.
Rename the moved functions to contain the __qt_internal prefix.
Also rename the existing QtPublicTargetsHelpers.cmake into
QtPlatformTargetHelpers.cmake to avoid confusion with the newly
introduced QtPublicTargetHelpers.cmake.
Task-number: QTBUG-92933
Change-Id: I48b5b6a8718a3424f59ca60f11fc9e97a809765d
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
