字符数组的文字字符串初始值设定项 [英] Literal string initializer for a character array

问题描述

对于数组衰减为指针的情况，规则如下:

In the following rules for the case when array decays to pointer:

出现在表达式中的array-of-T类型的左值[见问题2.5]衰减(三个例外)为指向其第一个元素的指针；结果指针的类型是指向T的指针.

An lvalue [see question 2.5] of type array-of-T which appears in an expression decays (with three exceptions) into a pointer to its first element; the type of the resultant pointer is pointer-to-T.

(例外情况是数组是 sizeof 或 & 运算符的操作数，或者是字符数组的文字字符串初始值设定项.)

(The exceptions are when the array is the operand of a sizeof or & operator, or is a literal string initializer for a character array.)

如何理解数组是字符数组的文字字符串初始化器"的情况?请举个例子.

How to understand the case when the array is "literal string initializer for a character array"? Some example please.

谢谢！

推荐答案

数组不会衰减为指针的三个例外如下:

The three exceptions where an array does not decay into a pointer are the following:

异常 1. — 当数组是 sizeof 的操作数时.

Exception 1. — When the array is the operand of sizeof.

int main()
{
   int a[10];
   printf("%zu", sizeof(a)); /* prints 10 * sizeof(int) */

   int* p = a;
   printf("%zu", sizeof(p)); /* prints sizeof(int*) */
}

异常 2. — 当数组是 & 运算符的操作数时.

Exception 2. — When the array is the operand of the & operator.

int main()
{
    int a[10];
    printf("%p", (void*)(&a)); /* prints the array's address */

    int* p = a;
    printf("%p", (void*)(&p)); /*prints the pointer's address */
}

异常 3. — 当数组用文字字符串初始化时.

Exception 3. — When the array is initialized with a literal string.

int main()
{
    char a[] = "Hello world"; /* the literal string is copied into a local array which is destroyed after that array goes out of scope */

    char* p = "Hello world"; /* the literal string is copied in the read-only section of memory (any attempt to modify it is an undefined behavior) */
}

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