用法3:const修饰函数传入参数 将函数传入参数声明为const,以指明使用这种参数仅仅是为了效率的原因,而不是想让调用函数能够修改对象的值。同理,将指针参数声明为const,函数将不修改由这个参数所指的对象。 通常修饰指针参数和引用参数: void Fun( const A *in); // 修饰指针型传入参数 void Fun(const A &in);
pc2 is a pointer to const char. 用法3:const修饰函数传入参数 将函数传入参数声明为const,以指明使用这种参数仅仅是为了效率的原因,而不是想让调用函数能够修改对象的值。同理,将指针参数声明为const,函数将不修改由这个参数所指的对象。 通常修饰指针参数和引用参数: void Fun( const A *in); // 修饰指针型...
One of the great use of volatile and const keyword together is at the time ofaccessing the GPIO registers. In the case of GPIO, its value will be changed by the ‘external factors’ (if a switch or any output device is attached with GPIO), if it is configured as an input. In that ...
In C, you use the type qualifier const to prevent code in an application from assigning a new value to a variable. In an application where an external actor (for example, a hardware device) can manipulate the value of a variable, you use the keyword volatile to prevent a compiler from ...
Does it ever make sense to declare a variable in C or C++ as both volatile (in other words, "ever-changing") and const ("read-only")? If so, why? And how should you combine volatile and const properly?Michael BarrInter-noise & Noise-con Congress & Conference...
4) const volatile int * volatile s4; 5) volatile int * (*f)(volatile int *); Check your answers. Summary The volatile keyword is relatively unknown. There are times when its use is required for correct operation of C/C++ programs. In general, whenever a variable may be altered asynchron...
in which case the Java Memory Model ensures that all threads see a consistent value for the variable 从这段描述中我们可以知道 volatile 的语义了,它可以修饰 Java 对象中的字段,一旦某个字段被 volatile 修饰了,那么 Java 虚拟机会保证它在多个线程之间的可见性,也就是说,一个线程修改了这个字段,那么其他...
a = 1; // C – write to a local = 1; // D’ – apply “constant propagation” This reordering is also legal according to the rules of the compiler. However, it’s easy to see how this can be a problem in a multi-threaded environment where another thread is writing toaconcurrently...
1.2 IN C/C++ 在C/C++语言中,使用 volatile 关键字声明的变量(或对象)通常具有与优化、多线程相关的特殊属性。通常,volatile 关键字用来阻止(伪)编译器对其认为的、无法“被代码本身”改变的代码(变量或对象)进行优化。如在C/C++中,volatile 关键字可以用来提醒编译器使用 volatile 声明的变量随时有可能改变,因此...
const and volatile objects When an object is first created, the cv-qualifiers used (which could be part ofdecl-specifier-seqor part of adeclaratorin adeclaration, or part oftype-idin anew-expression) determine the constness or volatility of the object, as follows: ...