c - 数组变量的 "value"是什么？

Question

我在一本书里有这个例子:

#define ALLOCSIZE 10000 /* size of available space */

static char allocbuf[ALLOCSIZE]; /* storage for alloc */
static char *allocp = allocbuf; /* next free position */

char *alloc(int n) /* return pointer to n characters */
{
    if (allocbuf + ALLOCSIZE - allocp >= n) { /* it fits */
        allocp += n;
        return allocp - n; /* old p */
    } else /* not enough room */
      return 0;
}

void afree(char *p) /* free storage pointed to by p */
{
     if (p >= allocbuf && p < allocbuf + ALLOCSIZE)
         allocp = p;
}

我需要知道 allocbuf 代表什么(它的值)，以便将其用于:

if (allocbuf + ALLOCSIZE - allocp >= n) 

Answer 1

引用 C11，第 §6.3.2.1/p3 章，(强调我的)

Except when it is the operand of the sizeof operator, the _Alignof operator, or the unary & operator, or is a string literal used to initialize an array, an expression that has type ‘‘array of type’’ is converted to an expression with type ‘‘pointer to type’’ that points to the initial element of the array object and is not an lvalue. [...]

因此，在您的代码中，allocbuf，它是一个数组类型，当用作

if (allocbuf + ALLOCSIZE - allocp >= n) {

将衰减到指向数组第一个元素的指针。