CMake: Port the reduce-relocations feature

As reduce-relocations implies bsymbolic_functions, we also add the
-Bsymbolic-functions linker flag.
Also, handle the .dynlist files that are passed to the linker by
bsymbolic_functions.prf in the qmake build.

Change-Id: I535c33fba888596d2f8975b16864bbe9f0a7caa4
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

1 files changed, 15 insertions, 0 deletions

diff --git a/cmake/QtBuild.cmake b/cmake/QtBuild.cmake
index 4c5a7a6019..8deb9b8cbd 100644
--- a/cmake/QtBuild.cmake
+++ b/cmake/QtBuild.cmake
@@ -1573,6 +1573,7 @@ function(qt_add_module target)
 
     ### Define Targets:
     set(is_interface_lib 0)
+    set(is_shared_lib 0)
     if(${arg_HEADER_MODULE})
         add_library("${target}" INTERFACE)
         set(is_interface_lib 1)
@@ -1580,6 +1581,7 @@ function(qt_add_module target)
         add_library("${target}" STATIC)
     elseif(${QT_BUILD_SHARED_LIBS})
         add_library("${target}" SHARED)
+        set(is_shared_lib 1)
     else()
         add_library("${target}" STATIC)
     endif()
@@ -1596,6 +1598,19 @@ function(qt_add_module target)
         )
     endif()
 
+    if(QT_FEATURE_reduce_relocations AND UNIX AND NOT is_interface_lib)
+        # On x86 and x86-64 systems with ELF binaries (especially Linux), due to
+        # a new optimization in GCC 5.x in combination with a recent version of
+        # GNU binutils, compiling Qt applications with -fPIE is no longer
+        # enough.
+        # Applications now need to be compiled with the -fPIC option if the Qt option
+        # \"reduce relocations\" is active.
+        target_compile_options(${target} INTERFACE -fPIC)
+        if(GCC AND is_shared_lib)
+            target_link_options(${target} PRIVATE LINKER:-Bsymbolic-functions)
+        endif()
+    endif()
+
     if (ANDROID)
         qt_android_apply_arch_suffix("${target}")
     endif()