From 7e7c9ba45554cd4c2f9a80ad61c3d2a0f9599f9b Mon Sep 17 00:00:00 2001
From: Joerg Bornemann <joerg.bornemann@qt.io>
Date: Fri, 21 Aug 2020 12:59:24 +0200
Subject: CMake: Support configure tests of type 'linkerSupportsFlag'

Task-number: QTBUG-86155
Change-Id: I3764d99cd4ad1c432b499ec9ba7c4c48391fa421
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
---
 cmake/QtFeature.cmake              | 28 ++++++++++++++++++++++++++++
 cmake/QtProcessConfigureArgs.cmake |  1 +
 configure.cmake                    | 10 ++++++++++
 util/cmake/configurejson2cmake.py  | 18 ++++++++++++++++++
 4 files changed, 57 insertions(+)

diff --git a/cmake/QtFeature.cmake b/cmake/QtFeature.cmake
index 5002a53352..66242548ed 100644
--- a/cmake/QtFeature.cmake
+++ b/cmake/QtFeature.cmake
@@ -881,6 +881,34 @@ function(qt_config_compiler_supports_flag_test name)
     set(TEST_${name} "${TEST_${name}}" CACHE INTERNAL "${label}")
 endfunction()
 
+function(qt_config_linker_supports_flag_test name)
+    if(DEFINED "TEST_${name}")
+        return()
+    endif()
+
+    cmake_parse_arguments(arg "" "LABEL;FLAG" "" ${ARGN})
+    set(flags "-Wl,${arg_FLAG}")
+
+    # Select the right linker.
+    if(GCC OR CLANG)
+        # TODO: This works for now but is... suboptimal. Once
+        # QTBUG-86186 is resolved, we should check the *features*
+        # QT_FEATURE_use_gold_linker etc. instead of trying to
+        # replicate the feature conditions.
+        if(QT_FEATURE_use_gold_linker_alias OR INPUT_linker STREQUAL "gold")
+            list(PREPEND flags "-fuse-ld=gold")
+        elseif(INPUT_linker STREQUAL "bfd")
+            list(PREPEND flags "-fuse-ld=bfd")
+        elseif(INPUT_linker STREQUAL "lld")
+            list(PREPEND flags "-fuse-ld=lld")
+        endif()
+    endif()
+
+    set(CMAKE_REQUIRED_LINK_OPTIONS ${flags})
+    check_cxx_source_compiles("int main() { return 0; }" TEST_${name})
+    set(TEST_${name} "${TEST_${name}}" CACHE INTERNAL "${label}")
+endfunction()
+
 function(qt_make_features_available target)
     if(NOT "${target}" MATCHES "^${QT_CMAKE_EXPORT_NAMESPACE}::[a-zA-Z0-9_-]*$")
         message(FATAL_ERROR "${target} does not match ${QT_CMAKE_EXPORT_NAMESPACE}::[a-zA-Z0-9_-]*. INVALID NAME.")
diff --git a/cmake/QtProcessConfigureArgs.cmake b/cmake/QtProcessConfigureArgs.cmake
index 7e3f789a7c..5e8e2677e7 100644
--- a/cmake/QtProcessConfigureArgs.cmake
+++ b/cmake/QtProcessConfigureArgs.cmake
@@ -97,6 +97,7 @@ defstub(qt_config_compile_test)
 defstub(qt_config_compile_test_machine_tuple)
 defstub(qt_config_compile_test_x86simd)
 defstub(qt_config_compiler_supports_flag_test)
+defstub(qt_config_linker_supports_flag_test)
 defstub(qt_configure_add_report_entry)
 defstub(qt_configure_add_summary_build_mode)
 defstub(qt_configure_add_summary_build_parts)
diff --git a/configure.cmake b/configure.cmake
index f6863d01fe..e4b632f0db 100644
--- a/configure.cmake
+++ b/configure.cmake
@@ -130,6 +130,16 @@ qt_config_compiler_supports_flag_test(optimize_debug
     FLAG "-Og"
 )
 
+qt_config_linker_supports_flag_test(enable_new_dtags
+    LABEL "new dtags support"
+    FLAG "--enable-new-dtags"
+)
+
+qt_config_linker_supports_flag_test(gdb_index
+    LABEL "gdb index support"
+    FLAG "--gdb-index"
+)
+
 # reduce_relocations
 qt_config_compile_test(reduce_relocations
     LABEL "-Bsymbolic-functions support"
diff --git a/util/cmake/configurejson2cmake.py b/util/cmake/configurejson2cmake.py
index ffe2dd11b7..8b74cf53cb 100755
--- a/util/cmake/configurejson2cmake.py
+++ b/util/cmake/configurejson2cmake.py
@@ -777,6 +777,14 @@ def write_compiler_supports_flag_test(
     cm_fh.write(lineify("FLAG", data.get("flag", "")))
     cm_fh.write(")\n\n")
 
+def write_linker_supports_flag_test(
+    ctx, name, details, data, cm_fh, manual_library_list=None, is_library_test=False
+):
+    cm_fh.write(f"qt_config_linker_supports_flag_test({featureName(name)}\n")
+    cm_fh.write(lineify("LABEL", data.get("label", "")))
+    cm_fh.write(lineify("FLAG", data.get("flag", "")))
+    cm_fh.write(")\n\n")
+
 def parseTest(ctx, test, data, cm_fh):
     skip_tests = {
         "c11",
@@ -814,6 +822,16 @@ def parseTest(ctx, test, data, cm_fh):
 
         write_compiler_supports_flag_test(ctx, test, details, data, cm_fh)
 
+    if data["type"] == "linkerSupportsFlag":
+        knownTests.add(test)
+
+        if "test" in data:
+            details = data["test"]
+        else:
+            details = test
+
+        write_linker_supports_flag_test(ctx, test, details, data, cm_fh)
+
     elif data["type"] == "libclang":
         knownTests.add(test)
 
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