C++模板与异常安全结合使用技巧

template <typename T>
class SafeContainer {
    T* data_;
    size_t size_;
public:
    explicit SafeContainer(size_t n) 
        : data_(new T[n]()), size_(n) {} // 可能抛出 bad_alloc
<pre class='brush:php;toolbar:false;'>~SafeContainer() { delete[] data_; }

SafeContainer(const SafeContainer& other)
    : data_(nullptr), size_(0)
{
    if (other.data_) {
        data_ = new T[other.size_]; // 若此处抛出，原对象不变
        std::uninitialized_copy(other.data_, other.data_ + other.size_, data_);
        size_ = other.size_;
    }
}

template <typename T>
class Vector {
    T* data_;
    size_t size_, capacity_;
<pre class='brush:php;toolbar:false;'>friend void swap(Vector& a, Vector& b) noexcept {
    using std::swap;
    swap(a.data_, b.data_);
    swap(a.size_, b.size_);
    swap(a.capacity_, b.capacity_);
}

template <typename T>
class Wrapper {
    T value_;
public:
    Wrapper(Wrapper&& other) noexcept(std::is_nothrow_move_constructible_v<T>)
        : value_(std::move(other.value_)) {}
<pre class='brush:php;toolbar:false;'>Wrapper& operator=(Wrapper&& other) noexcept(std::is_nothrow_move_assignable_v<T>) {
    value_ = std::move(other.value_);
    return *this;
}

~MyTemplate() {
    try {
        cleanup(); // 可能抛出
    } catch (...) {
        // 记录日志，但不抛出
    }
}