在C++中,noexcept是一个异常说明符,用于告知编译器一个函数是否会抛出异常。使用noexcept可以提供编译器有关函数异常处理的信息,从而优化代码。...noexcept有两种形式:noexcept和noexcept(expression)。 noexcept:表示函数不会抛出异常。...void func() noexcept { // 函数体 } 在这个例子中,函数func被声明为noexcept,意味着函数内部不会抛出任何异常。...int divide(int a, int b) noexcept(noexcept(a / b)) { return a / b; } 在这个例子中,函数divide的异常规范(noexcept...(noexcept(a / b)))是一个嵌套的noexcept表达式,它将根据表达式a / b是否会抛出异常来确定函数divide是否会抛出异常。
并提出了关键字noexcept用于指明函数保证自己不会发生异常。 用法 noexcept既可以表征普通函数不发射异常,也可以用于表征成员函数不发射异常。...,那么noexcept是如何保证的呢?...注意事项 只有在时间维度上恒为不发射异常的函数才可标注为noexcept,否则不要做出该函数noexcept的假设。...如果函数标注为noexcept,则该函数调用的所有函数应也是noexcept,否则不要做出该函数noexcept的假设。尽管noexcept调用非noexcept函数会通过编译但不推荐这样做。...释放内存的函数和析构函数默认为noexcept, 补充 noexcept可以作为操作符,用于检测函数是否被标记为noexcept,使用代码如下: void no_exception()noexcept
);自定义函数在没有加noexcept或noexcept(true)声明的时候,其默认是noexcept(false)。...noexcept operator前面提到的noexcept用法都是noexcept specifier,其实它还有另外一个用法是noexcept operator,用于判定一个表达式是否是noexcept...noexcept:" << noexcept(bar()) << endl; return 0;}运行后输出:foo() check noexcept:1bar() check noexcept...所以要使用noexcept(foo())而不是noexcept(foo)。...: bar is not noexcept11 | static_assert(noexcept(bar()), " bar is not noexcept");noexcept operator也可以用来检测
{ return; } auto block_throw = []() noexcept { no_throw(); }; int main() { std::cout <...< std::boolalpha << "may_throw() noexcept?..." << noexcept(may_throw()) << std::endl << "no_throw() noexcept?..." << noexcept(no_throw()) << std::endl << "lmay_throw() noexcept?..." << noexcept(non_block_throw()) << std::endl << "lno_throw() noexcept?
noexcept Reason(原因) To make error handling systematic, robust, and efficient....Example(示例) double compute(double d) noexcept { return log(sqrt(d <= 0 ?...通过将compute函数定义为noexcept,我向编译器和代码的读者传递了可以让它们更容易理解和维护代码的信息。...很多标准库函数被定义为noexcept,包含所有从C标准库继承的标准库函数。...这里的noexcept说明我不愿意或者不能处理局部的vecrot构建失败的情况。也就是说,我认为内存耗尽是严重的设计错误(和硬件错误同样看待),如果这种情况发生,我甘愿终止程序。
如果类的所有的成员的析构函数都是noexcept的,它的析构函数(无论是用户定义的还是编译器生成的)就会被隐式定义为noexcept(这和函数体内的具体代码无关)。...通过显式定义析构函数为noexcept,可以防止析构函数由于类成员被修改而无法成为noexcpet。...noexcept....因此,如果有疑问,就将析构函数定义为noexcept。 Note(注意) Why not then declare all destructors noexcept?...(简单)如果存在抛出异常的风险,则将析构函数定义为noexcept。
其函数声明如下: T* data() noexcept; //C++11 起, C++17 前 constexpr T* data() noexcept; //C++17 起 const T* data...() const noexcept; //C++11 起, C++17 前 constexpr const T* data() const noexcept; //C++17 起 其返回的指针使得范围...end() noexcept; //C++17 前 constexpr iterator end() noexcept; //C++17 起 const_iterator end() const noexcept...它们的声明如下: reverse_iterator rbegin() noexcept; //C++17 前 constexpr reverse_iterator rbegin() noexcept;...() const noexcept; //C++11 起 const_reverse_iterator crend() const noexcept; //C++11 起 2.2.4 容量 empty
_Get_first(); } _NODISCARD const _Dx& get_deleter() const noexcept { return _Mypair...._Myval2; } _NODISCARD pointer operator->() const noexcept { return _Mypair...._Myval2; } explicit operator bool() const noexcept { return static_cast(_Mypair....最后是三个对裸指针的直接操作: _NODISCARD pointer get() const noexcept { return _Mypair...._Myval2; } pointer release() noexcept { return _STD exchange(_Mypair.
: ptr_(nullptr) { } smart_ptr(const T &ptr) noexcept : ptr_(new T(ptr)) {...} smart_ptr(smart_ptr &rhs) noexcept { ptr_ = rhs.release(); // 释放所有权,此时rhs...的ptr_指针为nullptr } smart_ptr &operator=(smart_ptr rhs) noexcept { swap(rhs...); return *this; } void swap(smart_ptr &rhs) noexcept { // noexcept == throw...*ptr = ptr_; ptr_ = nullptr; return ptr; } T *get() const noexcept
显式bool转换函数 explicit operator bool() const noexcept { return data !...= nullptr); return *data; } pointer operator->() const noexcept { assert(data !...() noexcept { if (counter !...= nullptr); return data; } T& operator*() const noexcept { assert(data !...} // 返回当前计数器次数 int use_count() const noexcept { assert(counter !
C.66: Make move operations noexcept C.66:保证移动操作不会抛出异常 Reason(原因) A throwing move violates most people's...Example(示例) template class Vector { public: Vector(Vector&& a) noexcept :elem{a.elem}..., sz{a.sz} { a.sz = 0; a.elem = nullptr; } Vector& operator=(Vector&& a) noexcept { elem = a.elem...Enforcement(实施建议) (Simple) A move operation should be marked noexcept. (简单)移动操作应该被声明为noexcept。...https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c66-make-move-operations-noexcept
noexcept在标准库里部有很重要的应用,具体请阅读原书。 noexcept还是支持表达式计算的。...pair对象进行swap,当前仅当swap(first, p.first)和swap(second, p.second)都是noexcept时,pair::swap才是noexcept。...虽然noexcept很强大,但是乱用是不好的。...譬如如果你声明一个函数是noexcept,但有一天你反悔了,你可能想去掉noexcept声明,但这对客户端代码的影响不小,或者你不管noexcept声明了,硬是在函数里抛出异常!...一来,函数是底层函数,函数内部很可能没有调用其他函数,或者调用的函数也都是noexcept的,于是这个函数可以妥妥地加上noexcept。
=(const basic_string_view&) noexcept = default; template constexpr basic_string_view...; constexpr const_iterator end() const noexcept; constexpr const_iterator cbegin() const noexcept; constexpr...const_iterator cend() const noexcept; const_reverse_iterator rbegin() const noexcept; const_reverse_iterator...rend() const noexcept; const_reverse_iterator crbegin() const noexcept; const_reverse_iterator crend...() const noexcept; 其他核心函数: substr remove_prefix compare find ...
static size_t _S_buffer_size() _GLIBCXX_NOEXCEPT { return(__deque_buf_size( sizeof(_Tp) ) ); } __..._GLIBCXX_NOEXCEPT { return &(operator*()); } ★++与--操作符 ” // 前置++操作符 _Self & operator++() _GLIBCXX_NOEXCEPT...iterator end() _GLIBCXX_NOEXCEPT { return(this->_M_impl...._M_finish); } ★size()函数 ” size_type size() const _GLIBCXX_NOEXCEPT { return(this->_M_impl....bool empty() const _GLIBCXX_NOEXCEPT { return(this->_M_impl._M_finish == this->_M_impl.
array里面所有元素都填充为入参__u void fill(const value_type& __u); //swap是交换两个array数据 void swap(array& __other) noexcept...const_iterator(data() + _Nm); } _GLIBCXX17_CONSTEXPR const_reverse_iterator crbegin() const noexcept...max_size() const noexcept { return _Nm; } constexpr bool empty() const noexcept { return size() ==..., 0); } _GLIBCXX17_CONSTEXPR reference back() noexcept { return _Nm ?...*(end() - 1) : *end(); } constexpr const_reference back() const noexcept { return _Nm ?
: ptr_(new T()) { } smart_ptr(const T &ptr) noexcept : ptr_(new T(ptr)) {...} smart_ptr(smart_ptr &rhs) noexcept { ptr_ = rhs.release(); // 释放所有权,此时rhs...的ptr_指针为nullptr } void swap(smart_ptr &rhs) noexcept { // noexcept == throw() 保证不抛出异常...using std::swap; swap(ptr_, rhs.ptr_); } T *release() noexcept...此时再次拓展上述的代码: // move ctor smart_ptr(smart_ptr &&rhs) noexcept { std::cout << "move ctor" << std::
Note(注意) Deallocation functions, including operator delete, must be noexcept. swap functions must be...noexcept....Most destructors are implicitly noexcept by default. Also, make move operations noexcept....Catch such operations that are not noexcept. 捕捉抛出异常的析构函数,内存释放操作和swap函数。捕捉这些操作中没有声明为noexcept的情况。
C.83: For value-like types, consider providing a noexcept swap function C.83:对于值类类型,考虑提供一个不会抛出异常的交换函数...Example, good(示例) class Foo { public: void swap(Foo& rhs) noexcept { m1.swap(rhs.m1)...(Simple) When a class has a swap member function, it should be declared noexcept....(简单)如果一个类包含一个swap成员函数,这个函数应该被声明为noexcept。...isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c83-for-value-like-types-consider-providing-a-noexcept-swap-function
{ auto guard=lock.read_guard(); return map.max_size(); } iterator begin() noexcept...{ auto guard=lock.read_guard(); return map.cbegin(); } iterator end() noexcept...{ auto guard=lock.write_guard(); map.clear(); } void swap(map_type& __x) noexcept...( noexcept(map.swap(__x....另外在类中增加几个用于多线程环境的函数(见源码中的中文注释), 当你需要对map加锁时需要用到raii write_guard()noexcept和raii read_guard()const noexcept
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