c

202302, c

类型声明 #

char** args;
char **ap, *args[max];
ap = args;

char *args[max]; args是个数组, 数组有max个元素, 元素类型是指针类型, 指向char类型元素

Symbol	Meaning
static	1. Inside a function, retains its value between calls 2. At the function level, visible only in this file
extern	1. Applied to a function definition, has global scope (and is redundant) 2. Applied to a variable, defined elsewhere
void	1. As the return type of a function, doesn’t return a value 2. In a pointer declaration, the type of a generic pointer 3. In a parameter list, takes no parameters
*	1. The multiplication operator 2. Applied to a pointer, indirection 3. In a declaration, a pointer
&	1. Bitwise AND operator 2. Address-of operator
= ==	1.Assignment operator 2. Comparison operator
<= «=	1. Less-than-or-equal-to operator 2. Compound shift-left assignment operator
< <	1. Less-than operator 2. Left delimiter in #include directive
()	1. Enclose formal parameters in a function definition 2. Make a function call 3. Provide expression precedence 4. Convert (cast) a value to a different type 5. Define a macro with arguments 6.Make a macro call with arguments 7.Enclose the operand of the sizeof operator when it is a typename

Precedence problem	Expression	What People Expect	What They Actually Get
.的优先级高于* ->操作符用于消除这个问题	*p.f	p所指向对象的字段f (*p.f)	对p取f偏移, 作为指针, 然后进行解除引用操作 *(p.f)
[]高于*	int *ap[]	ap是个指向int数组的指针 int(*ap)[]	ap是个元素为int指针的数组 int *(ap[])
函数()高于*	int *fp()	fp是个函数指针, 所指函数返回int 即:int(*fp)()	fp是个函数, 返回 int* 即:int *(fp())
==和!=高于位操作运算符	(val & mask != 0)	(val & mask) != 0	val & (mask != 0)
==和!=高于赋值符	c=getchar() != EOF	(c=getchar()) != EOF	c = (getchar() != EOF)
算数运算符高于位运算符	msb « 4 + lsb	(msb « )4 + lsb	msb « (4 + lsb)
逗号运算符在所有运算符中优先级最低	i=1, 2	i=(1, 2)	(i=1), 2 其中2被丢弃

int i, a[10] 在内存由高位向地位分配时, i在高位, a[0]在最低位, 内存连续分配的, a[10]与i的地址相同, 具体内存分配由编译器实现不同而不同