Consider BUILD_SHARED_LIBS when adding libraries using _qt_internal_add_library

It does look safe to consider the value of BUILD_SHARED_LIBS in
_qt_internal_add_library. Current behavior might confuse users that
specify BUILD_SHARED_LIBS explicitly but get the library types
according to Qt build type.

[ChangeLog][CMake] qt6_add_library now considers the value of the
BUILD_SHARED_LIBS variable. If the variable is DEFINED it has
higher priority than the library type detecting logic in
qt6_add_library when adding the library targets.

Change-Id: I1c40e887c4e481424a596c870a8ff2784b08fcbb
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

3 files changed, 21 insertions, 20 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c774e297ab..5e38001cc6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -77,24 +77,24 @@ project(QtBase
     LANGUAGES CXX C ASM
 )
 
-# Should this Qt be static or dynamically linked?
-option(BUILD_SHARED_LIBS "Build Qt statically or dynamically" ON)
-set(QT_BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS})
-
-# This variable is also set in Qt6CoreConfigExtras.cmake, but it's not loaded when building
-# qtbase. Set it here so qt_add_plugin can compute the proper plugin flavor.
-set(QT6_IS_SHARED_LIBS_BUILD ${BUILD_SHARED_LIBS})
-
-# BUILD_SHARED_LIBS influences the minimum required CMake version. The value is set either by:
-#   a cache variable provided on the configure command line
-#   or set by QtAutoDetect.cmake depending on the platform
-#   or specified via a toolchain file that is loaded by the project() call
-#   or set by the option() call above
-include("${CMAKE_CURRENT_SOURCE_DIR}/cmake/QtCMakeVersionHelpers.cmake")
-include("${CMAKE_CURRENT_SOURCE_DIR}/cmake/QtPublicCMakeVersionHelpers.cmake")
-qt_internal_check_and_warn_about_unsuitable_cmake_version()
-
 if(NOT QT_BUILD_STANDALONE_TESTS)
+    # Should this Qt be static or dynamically linked?
+    option(BUILD_SHARED_LIBS "Build Qt statically or dynamically" ON)
+    set(QT_BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS})
+
+    # This variable is also set in Qt6CoreConfigExtras.cmake, but it's not loaded when building
+    # qtbase. Set it here so qt_add_plugin can compute the proper plugin flavor.
+    set(QT6_IS_SHARED_LIBS_BUILD ${BUILD_SHARED_LIBS})
+
+    # BUILD_SHARED_LIBS influences the minimum required CMake version. The value is set either by:
+    #   a cache variable provided on the configure command line
+    #   or set by QtAutoDetect.cmake depending on the platform
+    #   or specified via a toolchain file that is loaded by the project() call
+    #   or set by the option() call above
+    include("${CMAKE_CURRENT_SOURCE_DIR}/cmake/QtCMakeVersionHelpers.cmake")
+    include("${CMAKE_CURRENT_SOURCE_DIR}/cmake/QtPublicCMakeVersionHelpers.cmake")
+    qt_internal_check_and_warn_about_unsuitable_cmake_version()
+
     ## Add some paths to check for cmake modules:
     list(PREPEND CMAKE_MODULE_PATH
         "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
diff --git a/src/corelib/Qt6CoreMacros.cmake b/src/corelib/Qt6CoreMacros.cmake
index 57ff117b6d..e2b49900f7 100644
--- a/src/corelib/Qt6CoreMacros.cmake
+++ b/src/corelib/Qt6CoreMacros.cmake
@@ -2516,7 +2516,7 @@ function(_qt_internal_add_library target)
     # This in contrast to CMake which defaults to STATIC.
     if(NOT arg_STATIC AND NOT arg_SHARED AND NOT arg_MODULE AND NOT arg_INTERFACE
             AND NOT arg_OBJECT)
-        if(QT6_IS_SHARED_LIBS_BUILD)
+        if(BUILD_SHARED_LIBS OR (NOT DEFINED BUILD_SHARED_LIBS AND QT6_IS_SHARED_LIBS_BUILD))
             set(type_to_create SHARED)
         else()
             set(type_to_create STATIC)
diff --git a/src/corelib/doc/src/cmake/qt_add_library.qdoc b/src/corelib/doc/src/cmake/qt_add_library.qdoc
index 66336da4b9..ed6e770516 100644
--- a/src/corelib/doc/src/cmake/qt_add_library.qdoc
+++ b/src/corelib/doc/src/cmake/qt_add_library.qdoc
@@ -45,8 +45,9 @@ library type created depends on how Qt was built. If Qt was built statically,
 a static library will be created. Otherwise, a shared library will
 be created. Note that this is different to how CMake's \c{add_library()}
 command works, where the \c BUILD_SHARED_LIBS variable controls the type of
-library created. The \c{qt_add_library()} command does not consider
-\c BUILD_SHARED_LIBS when deciding the library type.
+library created. The \c{qt_add_library()} command considers
+\c BUILD_SHARED_LIBS when deciding the library type only if the variable is set
+explicitly.
 
 Any \c{sources} provided will be passed through to the internal call to
 \c{add_library()}.