mirrors/cosmopolitan
1
0
Fork 0
mirror of https://github.com/jart/cosmopolitan.git synced 2025-06-28 15:28:30 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

Fix bugs in in ctl::optional (#1203)

Browse source 
Manually manage the lifetime of `value_` by using an anonymous
`union`. This fixes a bunch of double-frees and double-constructs.

Additionally move the `present_` flag last. When `T` has padding
`present_` will be placed there saving `alignof(T)` bytes from
`sizeof(optional<T>)`.
This commit is contained in:
Alkis Evlogimenos 2024-06-08 02:47:24 +02:00 • committed by GitHub
parent 2ba6b0158f
commit d44a7dc603
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
2 changed files with 32 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

35
ctl/optional.h
View file

@ -14,38 +14,45 @@ class optional
public:
using value_type = T;
~optional() = default;
~optional()
{
if (present_)
value_.~T();
}
optional() noexcept : present_(false)
{
}
optional(const T& value) : present_(true), value_(value)
optional(const T& value) : present_(true)
{
new (&value_) T(value);
}
optional(T&& value) : present_(true), value_(std::move(value))
optional(T&& value) : present_(true)
{
new (&value_) T(std::move(value));
}
optional(const optional& other) : present_(other.present_)
{
if (present_)
if (other.present_)
new (&value_) T(other.value_);
}
optional(optional&& other) noexcept : present_(other.present_)
{
if (present_)
value_ = std::move(other.value_);
if (other.present_)
new (&value_) T(std::move(other.value_));
}
optional& operator=(const optional& other)
{
if (this != &other) {
reset();
if (other.present_)
new (&value_) T(other.value_);
present_ = other.present_;
if (present_)
value_ = other.value_;
}
return *this;
}
@ -53,9 +60,10 @@ class optional
optional& operator=(optional&& other) noexcept
{
if (this != &other) {
reset();
if (other.present_)
new (&value_) T(std::move(other.value_));
present_ = other.present_;
if (present_)
value_ = std::move(other.value_);
}
return *this;
}
@ -102,8 +110,9 @@ class optional
template<typename... Args>
void emplace(Args&&... args)
{
reset();
present_ = true;
value_ = T(std::forward<Args>(args)...);
new (&value_) T(std::forward<Args>(args)...);
}
void swap(optional& other) noexcept
@ -120,8 +129,10 @@ class optional
}
private:
union {
T value_;
};
bool present_;
T value_;
};
} // namespace ctl