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Fix undefined behaviour in base::weak_ptr.

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Regression was introduced in 1c79f85d00.

Invalid casts lead to crashes in macOS notifications handling.
Casts were T* -> has_weak_ptr* -> void* -> T* which was not working
in case T had has_weak_ptr as not first base class.

Now it uses just T* -> has_weak_ptr* -> T* casts.
This commit is contained in:
John Preston 2018-10-10 00:17:25 +03:00
parent 9436789d6d
commit b6128b6fe0
1 changed files with 9 additions and 13 deletions
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22
Telegram/SourceFiles/base/weak_ptr.h
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@ -11,14 +11,17 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
#include <memory>
namespace base {
class has_weak_ptr;
namespace details {
struct alive_tracker {
explicit alive_tracker(const void *value) : value(value) {
explicit alive_tracker(const has_weak_ptr *value) : value(value) {
}
std::atomic<int> counter = 1;
std::atomic<const void*> value;
std::atomic<const has_weak_ptr*> value;
};
inline alive_tracker *check_and_increment(alive_tracker *tracker) noexcept {
@ -36,8 +39,6 @@ inline void decrement(alive_tracker *tracker) noexcept {
} // namespace details
class has_weak_ptr;
template <typename T>
class weak_ptr;
@ -69,8 +70,7 @@ private:
details::alive_tracker *incrementAliveTracker() const {
auto current = _alive.load();
if (!current) {
auto alive = std::make_unique<details::alive_tracker>(
static_cast<const void*>(this));
auto alive = std::make_unique<details::alive_tracker>(this);
if (_alive.compare_exchange_strong(current, alive.get())) {
return alive.release();
}
@ -178,15 +178,11 @@ public:
}
T *get() const noexcept {
const auto strong = _alive ? _alive->value.load() : nullptr;
if constexpr (std::is_const_v<T>) {
return _alive
? static_cast<T*>(_alive->value.load())
: nullptr;
return static_cast<T*>(strong);
} else {
return _alive
? const_cast<T*>(
static_cast<const T*>(_alive->value.load()))
: nullptr;
return const_cast<T*>(static_cast<const T*>(strong));
}
}
explicit operator bool() const noexcept {