CMake: Move QT_HOST_PATH check and computation into Qt6 package

Instead of trying to compute and validate the QT_HOST_PATH and
QT_HOST_PATH_CMAKE_DIR variables in the generated toolchain file,
do it in the Qt6 package.

This provides better error messages when a project is configured
without using the Qt generated toolchain file.
Because it's not done in the toolchain anymore, remove the various
host variables from __qt_toolchain_used_variables.

Pick-to: 6.4
Task-number: QTBUG-104998
Change-Id: I1ca239ff83b8f783897e171fee352fc43e8ad7a8
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>

cmake/QtConfigDependencies.cmake.in

@@ -1,6 +1,13 @@
 set(@INSTALL_CMAKE_NAMESPACE@_FOUND FALSE)
 
 set(__qt_platform_requires_host_info_package "@platform_requires_host_info_package@")
+set(__qt_platform_initial_qt_host_path "@qt_host_path_absolute@")
+set(__qt_platform_initial_qt_host_path_cmake_dir "@qt_host_path_cmake_dir_absolute@")
+
+_qt_internal_setup_qt_host_path(
+    "${__qt_platform_requires_host_info_package}"
+    "${__qt_platform_initial_qt_host_path}"
+    "${__qt_platform_initial_qt_host_path_cmake_dir}")
 _qt_internal_find_host_info_package(${__qt_platform_requires_host_info_package})
 
 # note: _third_party_deps example: "ICU\\;FALSE\\;1.0\\;i18n uc data;ZLIB\\;FALSE\\;\\;"

cmake/QtPostProcessHelpers.cmake

@@ -371,6 +371,14 @@ endif()")
 
     _qt_internal_determine_if_host_info_package_needed(platform_requires_host_info_package)
 
+    if(platform_requires_host_info_package)
+        # TODO: Figure out how to make the initial QT_HOST_PATH var relocatable in relation
+        # to the target CMAKE_INSTALL_DIR, if at all possible to do so in a reliable way.
+        get_filename_component(qt_host_path_absolute "${QT_HOST_PATH}" ABSOLUTE)
+        get_filename_component(qt_host_path_cmake_dir_absolute
+            "${Qt${PROJECT_VERSION_MAJOR}HostInfo_DIR}/.." ABSOLUTE)
+    endif()
+
     if(third_party_deps OR platform_requires_host_info_package)
         # Setup build and install paths.
         set(path_suffix "${INSTALL_CMAKE_NAMESPACE}")

cmake/QtPublicDependencyHelpers.cmake

@@ -194,7 +194,11 @@ endmacro()
 
 function(_qt_internal_determine_if_host_info_package_needed out_var)
     set(needed FALSE)
-    if(NOT "${QT_HOST_PATH}" STREQUAL "")
+
+    # If a QT_HOST_PATH is provided when configuring qtbase, we assume it's a cross build
+    # and thus we require the QT_HOST_PATH to be provided also when using the cross-built Qt.
+    # This tells the QtConfigDependencies file to do appropriate requirement checks.
+    if(NOT "${QT_HOST_PATH}" STREQUAL "" AND NOT QT_NO_REQUIRE_HOST_PATH_CHECK)
         set(needed TRUE)
     endif()
     set(${out_var} "${needed}" PARENT_SCOPE)
@@ -211,3 +215,73 @@ macro(_qt_internal_find_host_info_package platform_requires_host_info)
                      NO_DEFAULT_PATH)
     endif()
 endmacro()
+
+macro(_qt_internal_setup_qt_host_path
+        host_path_required
+        initial_qt_host_path
+        initial_qt_host_path_cmake_dir
+    )
+    # Set up QT_HOST_PATH and do sanity checks.
+    # A host path is required when cross-compiling but optional when doing a native build.
+    # Requiredness can be overridden via variable.
+    if(DEFINED QT_REQUIRE_HOST_PATH_CHECK)
+        set(_qt_platform_host_path_required "${QT_REQUIRE_HOST_PATH_CHECK}")
+    else()
+        set(_qt_platform_host_path_required "${host_path_required}")
+    endif()
+
+    if(_qt_platform_host_path_required)
+        # QT_HOST_PATH precedence:
+        # - cache variable / command line option
+        # - environment variable
+        # - initial QT_HOST_PATH when qtbase was configured (and the directory exists)
+        if(NOT DEFINED QT_HOST_PATH)
+            if(DEFINED ENV{QT_HOST_PATH})
+                set(QT_HOST_PATH "$ENV{QT_HOST_PATH}" CACHE PATH "")
+            elseif(NOT "${initial_qt_host_path}" STREQUAL "" AND EXISTS "${initial_qt_host_path}")
+                set(QT_HOST_PATH "${initial_qt_host_path}" CACHE PATH "")
+            endif()
+        endif()
+
+        if(NOT QT_HOST_PATH STREQUAL "")
+            get_filename_component(_qt_platform_host_path_absolute "${QT_HOST_PATH}" ABSOLUTE)
+        endif()
+
+        if("${QT_HOST_PATH}" STREQUAL "" OR NOT EXISTS "${_qt_platform_host_path_absolute}")
+            message(FATAL_ERROR
+                "To use a cross-compiled Qt, please set the QT_HOST_PATH cache variable to the "
+                "location of your host Qt installation.")
+        endif()
+
+        # QT_HOST_PATH_CMAKE_DIR is needed to work around the rerooting issue when looking for host
+        # tools. See REROOT_PATH_ISSUE_MARKER.
+        # Prefer initially configured path if none was explicitly set.
+        if(NOT DEFINED QT_HOST_PATH_CMAKE_DIR)
+            if(NOT "${initial_qt_host_path_cmake_dir}" STREQUAL ""
+                  AND EXISTS "${initial_qt_host_path_cmake_dir}")
+                set(QT_HOST_PATH_CMAKE_DIR "${initial_qt_host_path_cmake_dir}" CACHE PATH "")
+            else()
+                # First try to auto-compute the location instead of requiring to set
+                # QT_HOST_PATH_CMAKE_DIR explicitly.
+                set(__qt_candidate_host_path_cmake_dir "${QT_HOST_PATH}/lib/cmake")
+                if(__qt_candidate_host_path_cmake_dir
+                        AND EXISTS "${__qt_candidate_host_path_cmake_dir}")
+                    set(QT_HOST_PATH_CMAKE_DIR
+                        "${__qt_candidate_host_path_cmake_dir}" CACHE PATH "")
+                endif()
+            endif()
+        endif()
+
+        if(NOT QT_HOST_PATH_CMAKE_DIR STREQUAL "")
+            get_filename_component(_qt_platform_host_path_cmake_dir_absolute
+                                   "${QT_HOST_PATH_CMAKE_DIR}" ABSOLUTE)
+        endif()
+
+        if("${QT_HOST_PATH_CMAKE_DIR}" STREQUAL ""
+                OR NOT EXISTS "${_qt_platform_host_path_cmake_dir_absolute}")
+            message(FATAL_ERROR
+                "To use a cross-compiled Qt, please set the QT_HOST_PATH_CMAKE_DIR cache variable "
+                "to the location of your host Qt installation lib/cmake directory.")
+        endif()
+    endif()
+endmacro()

cmake/QtToolchainHelpers.cmake

@@ -2,21 +2,6 @@
 # as well as CMake application projects.
 # Expects various global variables to be set.
 function(qt_internal_create_toolchain_file)
-    set(qt_host_path_required FALSE)
-
-    if(NOT "${QT_HOST_PATH}" STREQUAL "")
-        # If a QT_HOST_PATH is provided when configuring qtbase, we assume it's a cross build
-        # and thus we require the QT_HOST_PATH to be provided also when using the cross-built Qt.
-        # This tells the Qt toolchain file to do appropriate requirement checks.
-        set(qt_host_path_required TRUE)
-
-        # TODO: Figure out how to make the initial QT_HOST_PATH var relocatable in relation
-        # to the target CMAKE_INSTALL_DIR, if at all possible to do so in a reliable way.
-        get_filename_component(qt_host_path_absolute "${QT_HOST_PATH}" ABSOLUTE)
-        get_filename_component(qt_host_path_cmake_dir_absolute
-            "${Qt${PROJECT_VERSION_MAJOR}HostInfo_DIR}/.." ABSOLUTE)
-    endif()
-
     if(CMAKE_TOOLCHAIN_FILE)
         file(TO_CMAKE_PATH "${CMAKE_TOOLCHAIN_FILE}" __qt_chainload_toolchain_file)
         set(init_original_toolchain_file

cmake/qt.toolchain.cmake.in

@@ -3,11 +3,7 @@ set(__qt_toolchain_used_variables
     QT_TOOLCHAIN_INCLUDE_FILE
     QT_TOOLCHAIN_RELOCATABLE_CMAKE_DIR
     QT_TOOLCHAIN_RELOCATABLE_PREFIX
-    QT_HOST_PATH
-    QT_HOST_PATH_CMAKE_DIR
-    QT_REQUIRE_HOST_PATH_CHECK
     QT_ADDITIONAL_PACKAGES_PREFIX_PATH
-    QT_ADDITIONAL_HOST_PACKAGES_PREFIX_PATH
 )
 @init_additional_used_variables@
 
@@ -154,73 +150,6 @@ if(QT_TOOLCHAIN_INCLUDE_FILE)
     endif()
 endif()
 
-# Set up QT_HOST_PATH and do sanity checks.
-# A host path is required when cross-compiling but optional when doing a native build.
-# Requiredness can be overridden via variable.
-if(DEFINED QT_REQUIRE_HOST_PATH_CHECK)
-    set(__qt_toolchain_host_path_required "${QT_REQUIRE_HOST_PATH_CHECK}")
-else()
-    set(__qt_toolchain_host_path_required "@qt_host_path_required@")
-endif()
-set(__qt_toolchain_initial_qt_host_path
-    "@qt_host_path_absolute@")
-set(__qt_toolchain_initial_qt_host_path_cmake_dir
-    "@qt_host_path_cmake_dir_absolute@")
-
-# QT_HOST_PATH precedence:
-# - cache variable / command line option
-# - environment variable
-# - initial QT_HOST_PATH when qtbase was configured (and the directory exists)
-if(NOT DEFINED QT_HOST_PATH)
-    if(DEFINED ENV{QT_HOST_PATH})
-        set(QT_HOST_PATH "$ENV{QT_HOST_PATH}" CACHE PATH "")
-    else(__qt_toolchain_initial_qt_host_path AND EXISTS "${__qt_toolchain_initial_qt_host_path}")
-        set(QT_HOST_PATH "${__qt_toolchain_initial_qt_host_path}" CACHE PATH "")
-    endif()
-endif()
-
-if(NOT QT_HOST_PATH STREQUAL "")
-    get_filename_component(__qt_toolchain_host_path_absolute "${QT_HOST_PATH}" ABSOLUTE)
-endif()
-
-if(__qt_toolchain_host_path_required AND
-      ("${QT_HOST_PATH}" STREQUAL "" OR NOT EXISTS "${__qt_toolchain_host_path_absolute}"))
-    message(FATAL_ERROR
-        "To use a cross-compiled Qt, please set the QT_HOST_PATH cache variable to the location "
-        "of your host Qt installation.")
-endif()
-
-# QT_HOST_PATH_CMAKE_DIR is needed to work around the rerooting issue when looking for host tools
-# See REROOT_PATH_ISSUE_MARKER.
-# Prefer initially configured path if none was explicitly set.
-if(__qt_toolchain_host_path_required AND NOT DEFINED QT_HOST_PATH_CMAKE_DIR)
-    if(__qt_toolchain_initial_qt_host_path_cmake_dir
-          AND EXISTS "${__qt_toolchain_initial_qt_host_path_cmake_dir}")
-        set(QT_HOST_PATH_CMAKE_DIR "${__qt_toolchain_initial_qt_host_path_cmake_dir}" CACHE PATH "")
-    else()
-        # First try to auto-compute the location instead of requiring to set QT_HOST_PATH_CMAKE_DIR
-        # explicitly.
-        set(__qt_candidate_host_path_cmake_dir "${QT_HOST_PATH}/lib/cmake")
-        if(__qt_candidate_host_path_cmake_dir AND EXISTS "${__qt_candidate_host_path_cmake_dir}")
-            set(QT_HOST_PATH_CMAKE_DIR
-                "${__qt_candidate_host_path_cmake_dir}" CACHE PATH "")
-        endif()
-    endif()
-endif()
-
-if(NOT QT_HOST_PATH_CMAKE_DIR STREQUAL "")
-    get_filename_component(__qt_toolchain_host_path_cmake_dir_absolute
-                           "${QT_HOST_PATH_CMAKE_DIR}" ABSOLUTE)
-endif()
-
-if(__qt_toolchain_host_path_required AND
-      ("${QT_HOST_PATH_CMAKE_DIR}" STREQUAL ""
-       OR NOT EXISTS "${__qt_toolchain_host_path_cmake_dir_absolute}"))
-    message(FATAL_ERROR
-        "To use a cross-compiled Qt, please set the QT_HOST_PATH_CMAKE_DIR cache variable to "
-        "the location of your host Qt installation lib/cmake directory.")
-endif()
-
 # Store initial build type (if any is specified) to be read by QtBuildInternals.cmake when building
 # a Qt repo, standalone tests or a single test.
 if(DEFINED CACHE{CMAKE_BUILD_TYPE})