146 lines
5.6 KiB
Diff
146 lines
5.6 KiB
Diff
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From 7a2d2a1c3b66308cf03a00757f8fd97f043ccde4 Mon Sep 17 00:00:00 2001
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From: Thiago Macieira <thiago.macieira@intel.com>
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Date: Tue, 2 Jun 2015 11:30:57 -0700
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Subject: [PATCH] Add an automatic use of the ELF-versioned QtCore symbol
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See the comment in the header for an explanation of what it does.
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This trick is enabled for every single .o that is compiled, unless
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QT_NO_VERSION_TAGGING is defined. The assembly expands to a COMDAT
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section, which is mergeable by the linker, so only one copy of the
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output is present in the ELF module.
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The next commit will add a configure-time option to set
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QT_NO_VERSION_TAGGING to qconfig.h.
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This is enabled only for Linux and x86 / x86-64 / x32 due to the
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requirement of writing assembly and relocations, so it needs to be
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tested on each platform, which I have not done. It probably works on the
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BSDs too and might work on Solaris/x86, but again it requires
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testing. Support for other architectures requires different assembly
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output and relocations and can be added as needed, but they are not as
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important since this trick is has most value on desktop systems.
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Change-Id: I049a653beeb5454c9539ffff13e3ff5782a8cb86
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---
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src/corelib/global/global.pri | 3 +-
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src/corelib/global/qglobal.h | 1 +
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src/corelib/global/qversiontagging.h | 80 ++++++++++++++++++++++++++++++++++++
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3 files changed, 83 insertions(+), 1 deletion(-)
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create mode 100644 src/corelib/global/qversiontagging.h
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diff --git a/src/corelib/global/global.pri b/src/corelib/global/global.pri
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index fdbebca..9f31fb9 100644
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--- a/src/corelib/global/global.pri
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+++ b/src/corelib/global/global.pri
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@@ -17,7 +17,8 @@ HEADERS += \
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global/qisenum.h \
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global/qtypetraits.h \
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global/qflags.h \
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- global/qhooks_p.h
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+ global/qhooks_p.h \
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+ global/qversiontagging.h
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SOURCES += \
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global/archdetect.cpp \
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diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h
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index c4e2f76..e7995ac 100644
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--- a/src/corelib/global/qglobal.h
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+++ b/src/corelib/global/qglobal.h
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@@ -1103,6 +1103,7 @@ QT_END_NAMESPACE
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#include <QtCore/qatomic.h>
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#include <QtCore/qglobalstatic.h>
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#include <QtCore/qnumeric.h>
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+#include <QtCore/qversiontagging.h>
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#endif /* __cplusplus */
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diff --git a/src/corelib/global/qversiontagging.h b/src/corelib/global/qversiontagging.h
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new file mode 100644
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index 0000000..94246dd
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--- /dev/null
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+++ b/src/corelib/global/qversiontagging.h
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@@ -0,0 +1,80 @@
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+/****************************************************************************
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+**
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+** Copyright (C) 2015 Intel Corporation.
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+** Contact: http://www.qt.io/licensing/
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+**
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+** This file is part of the QtCore module of the Qt Toolkit.
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+**
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+** $QT_BEGIN_LICENSE:LGPL21$
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+** Commercial License Usage
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+** Licensees holding valid commercial Qt licenses may use this file in
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+** accordance with the commercial license agreement provided with the
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+** Software or, alternatively, in accordance with the terms contained in
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+** a written agreement between you and The Qt Company. For licensing terms
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+** and conditions see http://www.qt.io/terms-conditions. For further
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+** information use the contact form at http://www.qt.io/contact-us.
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+**
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+** GNU Lesser General Public License Usage
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+** Alternatively, this file may be used under the terms of the GNU Lesser
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+** General Public License version 2.1 or version 3 as published by the Free
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+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
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+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
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+** following information to ensure the GNU Lesser General Public License
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+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
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+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
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+**
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+** As a special exception, The Qt Company gives you certain additional
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+** rights. These rights are described in The Qt Company LGPL Exception
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+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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+**
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+** $QT_END_LICENSE$
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+**
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+****************************************************************************/
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+
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+// qglobal.h includes this header, so keep it outside of our include guards
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+#include <QtCore/qglobal.h>
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+
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+#if !defined(QVERSIONTAGGING_H) && !defined(QT_NO_VERSION_TAGGING)
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+#define QVERSIONTAGGING_H
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+
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+QT_BEGIN_NAMESPACE
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+
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+/*
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+ * Ugly hack warning and explanation:
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+ *
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+ * This file causes all ELF modules, be they libraries or applications, to use the
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+ * qt_version_tag symbol that is present in QtCore. Such symbol is versioned,
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+ * so the linker will automatically pull the current Qt version and add it to
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+ * the ELF header of the library/application. The assembly produces one section
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+ * called ".qtversion" containing two pointer-sized values. The first is a
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+ * relocation to the qt_version_tag symbol (which is what causes the ELF
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+ * version to get used). The second value is the current Qt version at the time
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+ * of compilation.
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+ *
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+ * There will only be one copy of the section in the output library or application.
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+ */
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+
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+#if defined(QT_BUILD_CORE_LIB)
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+// skip
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+#elif defined(Q_CC_GNU)
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+# if defined(Q_PROCESSOR_X86) && defined(Q_OS_LINUX)
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+asm (
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+".section .qtversion, \"aG\", @progbits, qt_version_tag, comdat\n"
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+".align 8\n"
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+# ifdef __LP64__
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+".quad " QT_STRINGIFY(QT_MANGLE_NAMESPACE(qt_version_tag)) "@GOTPCREL\n"
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+# elif defined(Q_PROCESSOR_X86_64) // x32
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+".long " QT_STRINGIFY(QT_MANGLE_NAMESPACE(qt_version_tag)) "@GOTPCREL\n"
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+# else // x86
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+".long " QT_STRINGIFY(QT_MANGLE_NAMESPACE(qt_version_tag)) "@GOT\n"
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+#endif
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+".long " QT_STRINGIFY(QT_VERSION) "\n"
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+".align 8\n"
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+".previous"
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+);
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+# endif
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+#endif
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+
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+QT_END_NAMESPACE
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+
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+#endif // QVERSIONTAGGING_H && !QT_NO_VERSION_TAGGING
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--
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2.3.5
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