CMake: Fix linkage with lld 16.0

lld 16.0 is more picky about symbol versioning than previous versions
(and other linkers such as ld.bfd, gold or mold).
It now errors out if a symbol is versioned but not defined
(see 8796677de8900dc154aef45f8620c3f987a40291).

Outside of detecting support for symbol versioning (fixed by 462832),
this causes linking Qt6 libraries other than Qt6Core to fail because
their linker scripts try to add versioning to qt_version_tag, which is
defined in Qt6Core rather than the library being linked.

The obvious (and working) fix is to version qt_version_tag only where it is
defined (Qt6Core), but this is not what the original intent seems to be.

Task-number: QTBUG-111514
Change-Id: I963d417befb0f6b2260c57f059eeda1fe79200c9
Reviewed-by: Alexandru Croitor <[email protected]>
(cherry picked from commit 8f8be55c155edcfbec8b798d4eb7e084ae88bc88)

3 files changed, 33 insertions, 14 deletions

diff --git a/cmake/QtFlagHandlingHelpers.cmake b/cmake/QtFlagHandlingHelpers.cmake
index edc1080d5f9..6784232ca9c 100644
--- a/cmake/QtFlagHandlingHelpers.cmake
+++ b/cmake/QtFlagHandlingHelpers.cmake
@@ -33,22 +33,15 @@ function(qt_internal_add_linker_version_script target)
         endif()
         string(APPEND contents "};\n")
         set(current "Qt_${PROJECT_VERSION_MAJOR}")
-        if (QT_NAMESPACE STREQUAL "")
-            set(tag_symbol "qt_version_tag")
-        else()
-            set(tag_symbol "qt_version_tag_${QT_NAMESPACE}")
-        endif()
         string(APPEND contents "${current} { *; };\n")
 
-        foreach(minor_version RANGE ${PROJECT_VERSION_MINOR})
-            set(previous "${current}")
-            set(current "Qt_${PROJECT_VERSION_MAJOR}.${minor_version}")
-            if (minor_version EQUAL ${PROJECT_VERSION_MINOR})
-                string(APPEND contents "${current} { ${tag_symbol}; } ${previous};\n")
-            else()
-                string(APPEND contents "${current} {} ${previous};\n")
-            endif()
-        endforeach()
+        get_target_property(type ${target} TYPE)
+        if(NOT target_type STREQUAL "INTERFACE_LIBRARY")
+            set(property_genex "$<TARGET_PROPERTY:${target},_qt_extra_linker_script_content>")
+            set(check_genex "$<BOOL:${property_genex}>")
+            string(APPEND contents
+                "$<${check_genex}:${property_genex}>")
+        endif()
 
         set(infile "${CMAKE_CURRENT_BINARY_DIR}/${target}.version.in")
         set(outfile "${CMAKE_CURRENT_BINARY_DIR}/${target}.version")
diff --git a/cmake/QtTargetHelpers.cmake b/cmake/QtTargetHelpers.cmake
index 5e41240fdeb..6e7ff4535a4 100644
--- a/cmake/QtTargetHelpers.cmake
+++ b/cmake/QtTargetHelpers.cmake
@@ -14,6 +14,8 @@
 #     module, these files will raise a warning at configure time if the condition is not met.
 #   COMPILE_FLAGS
 #     Custom compilation flags.
+#   EXTRA_LINKER_SCRIPT_CONTENT
+#     Extra content that should be appended to a target linker script. Applicable for ld only.
 #   NO_PCH_SOURCES
 #     Skip the specified source files by PRECOMPILE_HEADERS feature.
 function(qt_internal_extend_target target)
@@ -36,6 +38,7 @@ function(qt_internal_extend_target target)
     )
     set(single_args
         PRECOMPILED_HEADER
+        EXTRA_LINKER_SCRIPT_CONTENT
     )
     set(multi_args
         ${__default_public_args}
@@ -236,6 +239,10 @@ function(qt_internal_extend_target target)
             ${sources_property} "${arg_CONDITION_INDEPENDENT_SOURCES}")
     endif()
 
+    if(arg_EXTRA_LINKER_SCRIPT_CONTENT)
+        set_target_properties(${target} PROPERTIES
+            _qt_extra_linker_script_content "${arg_EXTRA_LINKER_SCRIPT_CONTENT}")
+    endif()
 endfunction()
 
 function(qt_is_imported_target target out_var)
diff --git a/src/corelib/CMakeLists.txt b/src/corelib/CMakeLists.txt
index 80e79146ae6..be7681bf7e7 100644
--- a/src/corelib/CMakeLists.txt
+++ b/src/corelib/CMakeLists.txt
@@ -1391,3 +1391,22 @@ if(APPLE AND QT_FEATURE_framework AND QT_FEATURE_separate_debug_info)
         DESTINATION "${dsym_script_install_dir}"
     )
 endif()
+
+set(linker_script_contents "")
+if (QT_NAMESPACE STREQUAL "")
+    set(tag_symbol "qt_version_tag")
+else()
+    set(tag_symbol "qt_version_tag_${QT_NAMESPACE}")
+endif()
+foreach(minor_version RANGE ${PROJECT_VERSION_MINOR})
+    set(previous "${current}")
+    set(current "Qt_${PROJECT_VERSION_MAJOR}.${minor_version}")
+    if (minor_version EQUAL ${PROJECT_VERSION_MINOR})
+        string(APPEND linker_script_contents "${current} { ${tag_symbol}; } ${previous};\n")
+    else()
+        string(APPEND linker_script_contents "${current} {} ${previous};\n")
+    endif()
+endforeach()
+qt_internal_extend_target(Core
+    EXTRA_LINKER_SCRIPT_CONTENT "${linker_script_contents}"
+)