From 438f088ad520ac91ae47dba9a515ab0d1088c89c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rg=20Krause?= <joerg.krause@embedded.rocks>
Date: Fri, 15 Apr 2016 03:32:02 +0200
Subject: [PATCH] Link with -ldl option only when it is supported
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`-ldl` option is used unconditionally in `QMAKE_LIBS_DYNLOAD` while libdl is
not supported when libc is static. As the value of `QMAKE_LIBS_DYNLOAD` goes
into 'Libs.private' field of the pkgconfig files created by qmake, static
linking with qt will fail with:
  /usr/bin/ld: cannot find -ldl

Fix this issue by adding a build test to configure to check if libdl is
supported. `QMAKE_LIBS_DYNLOAD` in "src/corelib/plugin/plugin.pri" is now used
only if libdl is available.

Backported from Qt5:
https://github.com/qtproject/qtbase/commit/f669ea0d54302de31456d57286aa0e4ca1443e98

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
---
 config.tests/unix/libdl/libdl.cpp | 39 +++++++++++++++++++++++++++++++++++++++
 config.tests/unix/libdl/libdl.pro |  3 +++
 configure                         |  6 ++++++
 src/corelib/plugin/plugin.pri     |  2 +-
 4 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 config.tests/unix/libdl/libdl.cpp
 create mode 100644 config.tests/unix/libdl/libdl.pro

diff --git a/config.tests/unix/libdl/libdl.cpp b/config.tests/unix/libdl/libdl.cpp
new file mode 100644
index 0000000..28a8233
--- /dev/null
+++ b/config.tests/unix/libdl/libdl.cpp
@@ -0,0 +1,39 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the config.tests of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <dlfcn.h>
+
+int main(int, char **)
+{
+    dlopen(0, 0);
+}
diff --git a/config.tests/unix/libdl/libdl.pro b/config.tests/unix/libdl/libdl.pro
new file mode 100644
index 0000000..a643934
--- /dev/null
+++ b/config.tests/unix/libdl/libdl.pro
@@ -0,0 +1,3 @@
+SOURCES = libdl.cpp
+CONFIG -= qt dylib
+LIBS += -ldl
\ No newline at end of file
diff --git a/configure b/configure
index 10ad7ca..1c70691 100755
--- a/configure
+++ b/configure
@@ -5506,6 +5506,12 @@ if [ "$CFG_LIBPNG" = "auto" ]; then
     fi
 fi
 
+# detect dl
+if ! compileTest unix/libdl "libdl"; then
+    QMakeVar add DEFINES QT_NO_DYNAMIC_LIBRARY
+    QMAKE_CONFIG="$QMAKE_CONFIG no-libdl"
+fi
+
 # detect accessibility
 if [ "$CFG_ACCESSIBILITY" = "auto" ]; then
     if [ "$XPLATFORM_SYMBIAN" = "yes" ]; then
diff --git a/src/corelib/plugin/plugin.pri b/src/corelib/plugin/plugin.pri
index eb7a7f7..c342f2e 100644
--- a/src/corelib/plugin/plugin.pri
+++ b/src/corelib/plugin/plugin.pri
@@ -32,4 +32,4 @@ integrity {
 	SOURCES += plugin/qlibrary_unix.cpp
 }
 
-LIBS_PRIVATE += $$QMAKE_LIBS_DYNLOAD
+!no-libdl: LIBS_PRIVATE += $$QMAKE_LIBS_DYNLOAD
-- 
2.8.0