#include <stdio.h> #include <threads.h> void do_once(void) { puts("called once"); } static once_flag flag = ONCE_FLAG_INIT; int func(void* data) { call_once(&flag, do_once); } int main(void) { thrd_t t1, t2, t3,
voidcall_once(std::once_flag&flag, Callable&&f, Args&&...args); (since C++11) Executes theCallableobjectfexactly once, even if called concurrently from several threads. In detail: If, by the timestd::call_onceis called,flagindicates thatfwas already called,std::call_oncereturns right away...
如果多个线程试图同时初始化同一静态局部变量,那么初始化严格发生一次(类似的行为也可对任意函数以std::call_once来达成)。 此功能特性的通常实现都会使用双检查锁定模式的变体,这使得对已初始化的局部静态变量检查的运行时开销减少为单次非原子的布尔比较。
call_oncestd::condition_variable创建条件变量等待条件变量被通知std::condition_variable::notify_onestd::condition_variable::notify_all获取线程的运行结果创建异步任务获取异步任务的返回值std::async 的额外参数返回值的状态多个返回值C++ 预处理器预处理器IncludesDefinesIfError宏令牌连接字符串化文件和行各种各样...
If multiple threads attempt to initialize the same static local variable concurrently, the initialization occurs exactly once (similar behavior can be obtained for arbitrary functions withstd::call_once). Usual implementations of this feature use variants of the double-checked locking pattern, which red...
Once we have a HepMC3::Reader instance and have checked that it can read events, we can loop over events and process each one like so: // re-open the file to start from the first event rdr = HepMC3::deduce_reader(inf); while (true) { // read an event and check that you haven...
std::once_flag flag; void foo() { } std::call_once(flag, foo); std::condition_variable 创建条件变量 std::condition_variable cond; 等待条件变量被通知 std::unique_lock<std::mutex> lock; extern bool predicate(); // 调用方式 1 cond.wait(lock); // 调用方式 2 cond.wait(lock, predicat...
Thema Support-Bibliothek Wenn das Makro konstanten__STDC_NO_THREADS__(C11)durch den Compiler definiert ist, werden die Header<threads.h>und alle hier aufgeführten Namen nicht vorgesehen . Original: If the macro constant__STDC_NO_THREADS__(C11)is defined by the compiler, the header<threads...
// Program to illustrate call by references.#include <iostream>usingnamespacestd;// function call by referencevoidfun(int&x) { x+=10; }intmain() {intm=100; fun(m); cout<<"\nValue of m is : "<<m<<endl;return0; } Output ...
std::once_flag flag; void foo() { } std::call_once(flag, foo); std::condition_variable 创建条件变量 std::condition_variable cond; 等待条件变量被通知 std::unique_lock<std::mutex> lock; extern bool predicate(); // 调用方式 1 cond.wait(lock); // 调用方式 2 cond.wait(lock, predic...