qt5base-lts/tests/auto/other/toolsupport/tst_toolsupport.cpp
Marc Mutz 5f1f0fe0b7 QDateTimePrivate: inherit QSharedData and other cleanups
Don't manage the ref-count yourself, as this requires the code to use
the QAtomic copy ctor, which we want to remove going forward. Using
QSharedData, we can let the compiler write the code for us.

Since 'ref' this way moves to the first spot in the list of effective
members, creating a 4B hole between itself and 'msecs', swap 'status'
and 'msecs' to fill the hole:

  offset:   0       8      16      24
            |       |       |       |
  without   v       v       v       v
  adj.mnt: |*R*|   | msecs | S | U | TZ....
  before:  | msecs | S | U |*R*|   | TZ...
  after:   |*R*| S | msecs | U |   | TZ....

This keeps the padding out of the critical first word, which improves
latency. That said, for accessing the members the old layout surely was
optimal. This layout optimizes copies and pessimizes access to 'msecs'
on 32-bit platforms without the Critical Word First optimization.

Requires adjustments to tst_toolsupport and the qhooks version.

Also default members using NSDMI, consequently drop the manual default
ctor.

Change-Id: I3c48e68694ad29b28a13aa47ea0f283fae52edd7
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
2019-08-07 20:09:13 +00:00

154 lines
4.4 KiB
C++

/****************************************************************************
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#include <QtTest>
//
// Note:
//
// When this test here fails and the change leading to the failure
// intentionally changed a private class, adjust the test here and bump
// the TypeInformationVersion field in src/corelib/global/qhooks.cpp
// in the same commit as the modification to the private class.
//
// Don't do this at home. This is test code, not production.
#define protected public
#define private public
#include <private/qdatetime_p.h>
#include <private/qfile_p.h>
#include <private/qfileinfo_p.h>
#include <private/qobject_p.h>
#include <qobject.h>
#if defined(Q_CC_GNU) || defined(Q_CC_MSVC)
#define RUN_MEMBER_OFFSET_TEST 1
#else
#define RUN_MEMBER_OFFSET_TEST 0
#endif
#if RUN_MEMBER_OFFSET_TEST
template <typename T, typename K>
size_t pmm_to_offsetof(T K:: *pmm)
{
#ifdef Q_CC_MSVC
// Even on 64 bit MSVC uses 4 byte offsets.
quint32 ret;
#else
size_t ret;
#endif
Q_STATIC_ASSERT(sizeof(ret) == sizeof(pmm));
memcpy(&ret, &pmm, sizeof(ret));
return ret;
}
#endif
class tst_toolsupport : public QObject
{
Q_OBJECT
private slots:
void offsets();
void offsets_data();
};
void tst_toolsupport::offsets()
{
QFETCH(size_t, actual);
QFETCH(int, expected32);
QFETCH(int, expected64);
size_t expect = sizeof(void *) == 4 ? expected32 : expected64;
QCOMPARE(actual, expect);
}
void tst_toolsupport::offsets_data()
{
QTest::addColumn<size_t>("actual");
QTest::addColumn<int>("expected32");
QTest::addColumn<int>("expected64");
{
QTestData &data = QTest::newRow("sizeof(QObjectData)")
<< sizeof(QObjectData);
data << 28 << 48; // vptr + 3 ptr + 2 int + ptr
}
#if RUN_MEMBER_OFFSET_TEST
{
QTestData &data = QTest::newRow("QObjectPrivate::extraData")
<< pmm_to_offsetof(&QObjectPrivate::extraData);
data << 28 << 48; // sizeof(QObjectData)
}
{
QTestData &data = QTest::newRow("QFileInfoPrivate::fileEntry")
<< pmm_to_offsetof(&QFileInfoPrivate::fileEntry);
data << 4 << 8;
}
{
QTestData &data = QTest::newRow("QFileSystemEntry::filePath")
<< pmm_to_offsetof(&QFileSystemEntry::m_filePath);
data << 0 << 0;
}
#ifdef Q_OS_LINUX
{
QTestData &data = QTest::newRow("QFilePrivate::fileName")
<< pmm_to_offsetof(&QFilePrivate::fileName);
#ifdef Q_PROCESSOR_X86
// x86 32-bit has weird alignment rules. Refer to QtPrivate::AlignOf in
// qglobal.h for more details.
data << 152 << 224;
#else
data << 156 << 224;
#endif
}
#endif
{
QTest::newRow("QDateTimePrivate::m_msecs")
<< pmm_to_offsetof(&QDateTimePrivate::m_msecs) << 8 << 8;
QTest::newRow("QDateTimePrivate::m_status")
<< pmm_to_offsetof(&QDateTimePrivate::m_status) << 4 << 4;
QTest::newRow("QDateTimePrivate::m_offsetFromUtc")
<< pmm_to_offsetof(&QDateTimePrivate::m_offsetFromUtc) << 16 << 16;
QTest::newRow("QDateTimePrivate::m_timeZone")
<< pmm_to_offsetof(&QDateTimePrivate::m_timeZone) << 20 << 24;
}
#endif // RUN_MEMBER_OFFSET_TEST
}
QTEST_APPLESS_MAIN(tst_toolsupport);
#include "tst_toolsupport.moc"