From e1de70933e3af47f5600ebe5a7b3930e26690c8a Mon Sep 17 00:00:00 2001
From: Tobias Hunger <tobias.hunger@qt.io>
Date: Mon, 4 Mar 2019 13:05:54 +0100
Subject: [PATCH] CMake: Handle gc-sections linker flags

Add a function to set gc-sections flags on the linker.

Change-Id: I9ac02364836d2aa8de239adb8d3a5d29659a4007
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
---
 cmake/QtBuild.cmake | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/cmake/QtBuild.cmake b/cmake/QtBuild.cmake
index 4fc60400f5..1cb8426b30 100644
--- a/cmake/QtBuild.cmake
+++ b/cmake/QtBuild.cmake
@@ -191,15 +191,6 @@ macro(qt_parse_all_arguments result type flags options multiopts)
 endmacro()
 
 
-function(qt_internal_add_link_flags target to_add)
-    get_target_property(flags "${target}" LINK_FLAGS)
-    if ("${flags}" STREQUAL "flags-NOTFOUND")
-        set(flags "")
-    endif()
-    string(APPEND flags " ${to_add}")
-    set_target_properties("${target}" PROPERTIES LINK_FLAGS "${flags}")
-endfunction()
-
 function(qt_internal_add_link_flags_no_undefined target)
     if (GCC OR CLANG)
         if(APPLE)
@@ -209,7 +200,26 @@ function(qt_internal_add_link_flags_no_undefined target)
         else()
             message(FATAL_ERROR "Platform linker doesn't support erroring upon encountering undefined symbols. Target:\"${target}\".")
         endif()
-        qt_internal_add_link_flags("${target}" "${no_undefined_flag}")
+        target_link_options("${target}" PRIVATE "${no_undefined_flag}")
+    endif()
+endfunction()
+
+function(qt_internal_add_link_flags_gc_sections target visibility)
+    set(possible_visibilities PRIVATE INTERFACE PUBLIC)
+    list(FIND possible_visibilities "${visibility}" known_visibility)
+    if (known_visibility EQUAL "-1")
+        message(FATAL_ERROR "Visibitily setting must be one of PRIVATE, INTERFACE or PUBLIC.")
+    endif()
+
+    if (GCC OR CLANG)
+        if(APPLE)
+            set(gc_sections_flag "-Wl,-dead_strip")
+        elseif(LINUX OR BSD OR SOLARIS OR WIN32)
+            set(gc_sections_flag "-Wl,--gc-sections")
+        else()
+            message(FATAL_ERROR "Platform linker doesn't support gc sections. Target:\"${target}\".")
+        endif()
+        target_link_options("${target}" ${visibility} "${gc_sections_flag}")
     endif()
 endfunction()
 
@@ -256,7 +266,7 @@ function(qt_internal_add_linker_version_script target)
                 WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
                 COMMENT "Generating version linker script"
             )
-            qt_internal_add_link_flags("${target}" "-Wl,--version-script,${outfile}")
+            target_link_options("${target}" PRIVATE "-Wl,--version-script,${outfile}")
         endif()
     endif()
 endfunction()