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IPC: QNativeIpcKey: fix big-endian builds

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We weren't using the LSB in big-endian builds because the bitfield was in
the wrong order: it was either using the MSB (in 32-bit builds) or
something in the middle for 64-bit. So use quintptr in the bitfield to
ensure proper sizing and correct the order.

Additionally, we now store the d "pointer" as a quintptr, so as to avoid
storing the actual pointer to QNativeIpcKeyPrivate with the LSB set.

Change-Id: Idd5e1bb52be047d7b4fffffd17506adb77d52805
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
This commit is contained in:
Thiago Macieira 2023-03-27 17:35:51 -06:00
parent e2a76797e0
commit 05ebf3e54b
1 changed files with 17 additions and 7 deletions
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24
src/corelib/ipc/qtipccommon.h
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@ -18,7 +18,7 @@ class QNativeIpcKey
{
Q_GADGET_EXPORT(Q_CORE_EXPORT)
public:
enum class Type : quint16 {
enum class Type : quintptr {
// 0 is reserved for the invalid type
// keep 1 through 0xff free, except for SystemV
SystemV = 0x51, // 'Q'
@ -57,7 +57,7 @@ public:
}
QNativeIpcKey(QNativeIpcKey &&other) noexcept
: d(other.d), key(std::move(other.key))
: d(std::exchange(other.d, 0)), key(std::move(other.key))
{
if (isSlowPath())
move_internal(std::move(other));
@ -81,7 +81,7 @@ public:
QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_PURE_SWAP(QNativeIpcKey)
void swap(QNativeIpcKey &other)
{
qt_ptr_swap(d, other.d);
std::swap(d, other.d);
key.swap(other.key);
}
@ -119,17 +119,27 @@ public:
private:
struct TypeAndFlags {
quint16 isExtended : 1;
#if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
// this is the LSB
quintptr isExtended : 1;
Type type : 15;
quint16 reserved;
#endif
quintptr reserved : sizeof(quintptr) * 8 - 16;
#if Q_BYTE_ORDER == Q_BIG_ENDIAN
Type type : 15;
quint16 isExtended : 1;
// this was the LSB
#endif
};
// Bit 0: if set, holds a pointer (with the LSB set); if clear, holds the
// the TypeAndFlags structure.
union {
QNativeIpcKeyPrivate *d = nullptr;
quintptr d = 0;
TypeAndFlags typeAndFlags;
static_assert(sizeof(typeAndFlags) <= sizeof(d));
static_assert(sizeof(typeAndFlags) == sizeof(d));
};
QString key;