GCC: avoid duplicating objects in linker command line

Long command lines are especially a problem when building statically in
MXE. This commit tries to replicate the logic employed by qmake, where
before adding a new object to the command line, all of its previous
appearences get removed.

Fixes: QBS-1273
Change-Id: I51c843c4a7cfc170ed4fab30deae6c4229690dd0
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

2 files changed, 13 insertions, 0 deletions

diff --git a/share/qbs/modules/cpp/CppModule.qbs b/share/qbs/modules/cpp/CppModule.qbs
index efda896da..bdd6d2750 100644
--- a/share/qbs/modules/cpp/CppModule.qbs
+++ b/share/qbs/modules/cpp/CppModule.qbs
@@ -191,6 +191,7 @@ Module {
     property bool useRPathLink
     property string rpathLinkFlag
     property bool discardUnusedData
+    property bool removeDuplicateLibraries: true
 
     property stringList assemblerFlags
     PropertyOptions {
diff --git a/share/qbs/modules/cpp/gcc.js b/share/qbs/modules/cpp/gcc.js
index 639191da6..574fe769b 100644
--- a/share/qbs/modules/cpp/gcc.js
+++ b/share/qbs/modules/cpp/gcc.js
@@ -80,8 +80,20 @@ function collectLibraryDependencies(product, isDarwin) {
     var objectByFilePath = {};
     var tagForLinkingAgainstSharedLib = product.cpp.imageFormat === "pe"
             ? "dynamiclibrary_import" : "dynamiclibrary";
+    var removeDuplicateLibraries = product.cpp.removeDuplicateLibraries
 
     function addObject(obj, addFunc) {
+        /* If the object is already known, remove its previous usage and insert
+         * it again in the new desired position. This preserves the order of
+         * the other objects, and is analogous to what qmake does (see the
+         * mergeLflags parameter in UnixMakefileGenerator::findLibraries()).
+         */
+        if (removeDuplicateLibraries && (obj.filePath in objectByFilePath)) {
+            var oldObj = objectByFilePath[obj.filePath];
+            var i = objects.indexOf(oldObj);
+            if (i >= 0)
+                objects.splice(i, 1);
+        }
         addFunc.call(objects, obj);
         objectByFilePath[obj.filePath] = obj;
     }