qversiontagging: Add Windows support
Details in the comment in the header. I haven't recently tested with
MSVC, but I designed this originally in 2015 when I did have access to
Visual Studio so I know it works (I've confirmed with Godbolt).
With MinGW, this produces assembly:
.globl qt_version_tag_used
.section .qtversion,"dr"
.linkonce same_size
.align 16
qt_version_tag_used:
.quad __imp_qt_version_tag_6_4
.quad 394240
394240 is 0x060400. The DLL import table contains:
0015f03c 0015f294 00000000 00000000 00165478 0016012c
DLL Name: Qt6Core.t.dll
vma: Hint/Ord Member-Name Bound-To
161318 7 _Z11qt_assert_xPKcS0_S0_i
...
164cf8 6073 qt_version_tag_6_4
Change-Id: I42e7ef1a481840699a8dffff1404f45b13f60ba6
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
bb10
Thiago Macieira
parent
b2edef557c
commit
13ad42c679
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@ -1,6 +1,6 @@
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/****************************************************************************
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**
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** Copyright (C) 2016 Intel Corporation.
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** Copyright (C) 2022 Intel Corporation.
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** Contact: https://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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@ -38,6 +38,7 @@
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****************************************************************************/
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#include "qglobal.h"
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#include "qversiontagging.h"
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#define SYM QT_MANGLE_NAMESPACE(qt_version_tag)
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//#define SSYM QT_STRINGIFY(SYM)
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@ -47,11 +48,18 @@
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Q_CORE_EXPORT extern const char sym ## _ ## m ## _ ## n = 0; \
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asm(".symver " QT_STRINGIFY(sym) "_" QT_STRINGIFY(m) "_" QT_STRINGIFY(n) ", " \
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QT_STRINGIFY(sym) separator "Qt_" QT_STRINGIFY(m) "." QT_STRINGIFY(n))
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#elif defined(Q_OS_WIN)
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# define make_versioned_symbol2(sym, m, n, separator) \
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Q_CORE_EXPORT extern const char sym ## _ ## m ## _ ## n = 0;
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#else
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# define make_versioned_symbol2(sym, m, n, separator)
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#endif
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#define make_versioned_symbol(sym, m, n, separator) make_versioned_symbol2(sym, m, n, separator)
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QT_BEGIN_NAMESPACE
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extern "C" {
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#if QT_VERSION_MINOR > 0
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make_versioned_symbol(SYM, QT_VERSION_MAJOR, 0, "@");
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@ -108,3 +116,7 @@ make_versioned_symbol(SYM, QT_VERSION_MAJOR, 15, "@");
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// the default version:
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make_versioned_symbol(SYM, QT_VERSION_MAJOR, QT_VERSION_MINOR, "@@");
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}
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static_assert(std::is_trivially_destructible_v<QtPrivate::QVersionTag>);
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QT_END_NAMESPACE
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@ -1,6 +1,6 @@
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/****************************************************************************
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**
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** Copyright (C) 2016 Intel Corporation.
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** Copyright (C) 2022 Intel Corporation.
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** Contact: https://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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@ -46,22 +46,93 @@
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QT_BEGIN_NAMESPACE
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/*
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* Ugly hack warning and explanation:
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* 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 32-bit 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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* This file causes all libraries, plugins, and applications that #include this
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* file to automatically pull in a symbol found in QtCore that encodes the
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* current Qt version number at the time of compilation. The relocation is
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* designed so that it's impossible for the dynamic linker to perform lazy
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* binding. Instead, it must resolve at load time or fail. That way, attempting
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* to load such a library or plugin while an older QtCore is loaded will fail.
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* Similarly, if an older QtCore is found when launching an application, the
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* application will fail to launch.
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*
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* It's also possible to inspect which version is required by decoding the
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* .qtversion section. The second pointer-sized variable is the required
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* version, for example, for Qt 6.4.1:
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*
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* Hex dump of section [18] '.qtversion', 16 bytes at offset 0x1ee48:
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* 0x00000000 b0ffffff ffffffff 01040600 00000000 ................
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* ^^^^^^^^ ^^^^^^^^
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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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* This functionality can be disabled by defining QT_NO_VERSION_TAGGING. It's
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* disabled if Qt was built statically.
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*
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* Windows notes:
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*
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* On Windows, the address of a __declspec(dllimport) variable is not a
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* constant expression, unlike Unix systems. So we instead use the address of
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* the import variable, which is created by prefixing the external name with
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* "__imp_". Using that variable causes an import of the corresponding symbol
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* from QtCore DLL.
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*
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* With MinGW (GCC and Clang), we use a C++17 inline variable, so the compiler
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* and linker automatically merge the variables. The "used" __attribute__
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* tells the compiler to always emit that variable, whether it's used or not.
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*
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* MSVC has no equivalent to that attribute, so instead we create an extern
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* const variable and tell the linker to merge them all via
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* __declspec(selectany).
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*
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* ELF notes (Linux, FreeBSD):
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*
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* The symbol in question is simply "qt_version_tag" in both QtCore and in
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* this ELF module, but it has an ELF version attached to it (see
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* qversiontagging.cpp and QtFlagHandlingHelpers.cmake). That way, the error
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* message from the dynamic linker will say it can't find version "Qt_6.x".
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*
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* This is currently implemented only for x86 by way of inline assembly. We
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* inform the the linker to merge all TUs' .qtversion sections by way of the
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* "comdat" attribute in the .section directive. The first pointer-sized
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* variable is a GOT reference to qt_version_tag (that is: the address of
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* qt_version_tag is stored in the .got section and the linker inserts the
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* displacement to that pointer).
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*/
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namespace QtPrivate {
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struct QVersionTag
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{
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const void *symbol;
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quintptr version;
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constexpr QVersionTag(const void *sym, int currentVersion = QT_VERSION)
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: symbol(sym), version(currentVersion)
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{}
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};
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}
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#if defined(QT_BUILD_CORE_LIB) || defined(QT_BOOTSTRAPPED) || defined(QT_NO_VERSION_TAGGING) || defined(QT_STATIC)
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// don't make tags in QtCore, bootstrapped systems or if the user asked not to
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#elif defined(Q_OS_WIN)
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# ifdef _WIN64
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// 64-bit calling convention does not prepend a _
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# define QT_MANGLE_IMPORT_PREFIX __imp_
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# else
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// 32-bit convention does prepend a _
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# define QT_MANGLE_IMPORT_PREFIX _imp__
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# endif
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# ifdef Q_CC_MSVC
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# pragma section(".qtversion",read,shared)
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# define QT_VERSION_TAG_SECTION __declspec(allocate(".qtversion"))
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# define QT_VERSION_TAG_ATTRIBUTE __declspec(selectany) extern const
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# else
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# define QT_VERSION_TAG_ATTRIBUTE __attribute__((used)) constexpr inline
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# endif
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# define QT_VERSION_TAG2(sym, imp) \
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extern "C" const char * const imp; \
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QT_VERSION_TAG_ATTRIBUTE QT_VERSION_TAG_SECTION QtPrivate::QVersionTag sym ## _used(&imp)
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# define QT_VERSION_TAG(sym, imp) QT_VERSION_TAG2(sym, imp)
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#elif defined(Q_CC_GNU) && !defined(Q_OS_ANDROID)
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# if defined(Q_PROCESSOR_X86) && (defined(Q_OS_LINUX) || defined(Q_OS_FREEBSD_KERNEL))
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# if defined(Q_PROCESSOR_X86_64) && QT_POINTER_SIZE == 8 // x86-64 64-bit
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@ -69,7 +140,7 @@ QT_BEGIN_NAMESPACE
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# else // x86 or x86-64 32-bit (x32)
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# define QT_VERSION_TAG_RELOC(sym) ".long " QT_STRINGIFY(QT_MANGLE_NAMESPACE(sym)) "@GOT\n"
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# endif
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# define QT_VERSION_TAG(sym) \
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# define QT_VERSION_TAG(sym, imp) \
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asm ( \
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".section .qtversion, \"aG\", @progbits, " QT_STRINGIFY(QT_MANGLE_NAMESPACE(sym)) ", comdat\n" \
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".align 8\n" \
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@ -81,8 +152,25 @@ QT_BEGIN_NAMESPACE
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# endif
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#endif
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#ifdef Q_OF_ELF
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# define QT_VERSION_TAG_SYMBOL(prefix, sym, m, n) sym
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#else
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# define QT_VERSION_TAG_SYMBOL2(prefix, sym, m, n) prefix ## sym ## _ ## m ## _ ## n
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# define QT_VERSION_TAG_SYMBOL(prefix, sym, m, n) QT_VERSION_TAG_SYMBOL2(prefix, sym, m, n)
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#endif
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#if defined(QT_VERSION_TAG)
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QT_VERSION_TAG(qt_version_tag);
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# ifndef QT_VERSION_TAG_SECTION
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# define QT_VERSION_TAG_SECTION __attribute__((section(".qtversion")))
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# endif
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# define QT_MANGLED_VERSION_TAG_IMPORT QT_VERSION_TAG_SYMBOL(QT_MANGLE_IMPORT_PREFIX, qt_version_tag, QT_VERSION_MAJOR, QT_VERSION_MINOR)
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# define QT_MANGLED_VERSION_TAG QT_VERSION_TAG_SYMBOL(, QT_MANGLE_NAMESPACE(qt_version_tag), QT_VERSION_MAJOR, QT_VERSION_MINOR)
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QT_VERSION_TAG(QT_MANGLED_VERSION_TAG, QT_MANGLED_VERSION_TAG_IMPORT);
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# undef QT_MANGLED_VERSION_TAG
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# undef QT_MANGLED_VERSION_TAG_IMPORT
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# undef QT_VERSION_TAG_SECTION
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#endif
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QT_END_NAMESPACE
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