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39
40// qglobal.h includes this header, so keep it outside of our include guards
41#include <QtCore/qglobal.h>
42
43#if !defined(QVERSIONTAGGING_H)
44#define QVERSIONTAGGING_H
45
46QT_BEGIN_NAMESPACE
47
48/*
49 * Ugly hack warning and explanation:
50 *
51 * This file causes all ELF modules, be they libraries or applications, to use the
52 * qt_version_tag symbol that is present in QtCore. Such symbol is versioned,
53 * so the linker will automatically pull the current Qt version and add it to
54 * the ELF header of the library/application. The assembly produces one section
55 * called ".qtversion" containing two 32-bit values. The first is a
56 * relocation to the qt_version_tag symbol (which is what causes the ELF
57 * version to get used). The second value is the current Qt version at the time
58 * of compilation.
59 *
60 * There will only be one copy of the section in the output library or application.
61 */
62
63#if defined(QT_BUILD_CORE_LIB) || defined(QT_BOOTSTRAPPED) || defined(QT_NO_VERSION_TAGGING) || defined(QT_STATIC)
64// don't make tags in QtCore, bootstrapped systems or if the user asked not to
65#elif defined(Q_CC_GNU) && !defined(Q_OS_ANDROID)
66# if defined(Q_PROCESSOR_X86) && (defined(Q_OS_LINUX) || defined(Q_OS_FREEBSD_KERNEL))
67# if defined(Q_PROCESSOR_X86_64) && QT_POINTER_SIZE == 8 // x86-64 64-bit
68# define QT_VERSION_TAG_RELOC(sym) ".quad " QT_STRINGIFY(QT_MANGLE_NAMESPACE(sym)) "@GOT\n"
69# else // x86 or x86-64 32-bit (x32)
70# define QT_VERSION_TAG_RELOC(sym) ".long " QT_STRINGIFY(QT_MANGLE_NAMESPACE(sym)) "@GOT\n"
71# endif
72# define QT_VERSION_TAG(sym) \
73 asm ( \
74 ".section .qtversion, \"aG\", @progbits, " QT_STRINGIFY(QT_MANGLE_NAMESPACE(sym)) ", comdat\n" \
75 ".align 8\n" \
76 QT_VERSION_TAG_RELOC(sym) \
77 ".long " QT_STRINGIFY(QT_VERSION) "\n" \
78 ".align 8\n" \
79 ".previous" \
80 )
81# endif
82#endif
83
84#if defined(QT_VERSION_TAG)
85QT_VERSION_TAG(qt_version_tag);
86#endif
87
88QT_END_NAMESPACE
89
90#endif // QVERSIONTAGGING_H
91

source code of qtbase/src/corelib/global/qversiontagging.h