C 關鍵字

C reserved keywords

存儲類型說明符 storage-class specifier

keywords	meaning
auto	automatic duration storage-class specifier with no linkage
extern	static duration storage-class specifier with either internal or more usually external linkage
register	automatic duration storage-class specifier with no linkage. Hints that the variable will be used heavily
static	static duration storage-class specifier with internal linkage at file scope and no linkage at block scope
	static array indices in function parameter declarations (since C99)

跳轉, 條件, 循環語句聲明符 statement declarator

keywords	meaning
break
continue
goto
return
if	if statement
else	if statement: alternative branch
switch	switch statement
case	switch statement: case labels
default	switch statement: efault case label
	type-generic expression: as the declaration of the default generic association(since C11)
do	do-while loop
for	for loop
while	while loop
	do-while loop: terminating condition of the loop

類型聲明符 type declarator

keywords	meaning
char
int
double
enum	enumeration type
float
inline	inline function specifier
struct	compound type
union
typedef
void	incomplete type
	in a function with no parameter or no return value

類型修飾符 type modifier

keywords	meaning
long	long type modifier
short	short type modifier
signed	signed type modifier
unsigned	unsigned type modifier

類型限定符 type qualifier

keywords	meaning
const	const type qualifier
restrict	restrict type qualifier
volatile	volatile type qualifier

操作符 operator

keywords	meaning
sizeof	sizeof operator

inline

1. 使用 inline 關鍵字聲明內聯函數 Inline function, 內聯函數在某些情況下類似於宏, 直接將代碼內嵌到調用它的父函數中
2. 編譯時需要指定優化等級爲 -O3 才能被內嵌, 也可以指定內嵌函數屬性 #pragma always_inline 強制內嵌
3. 使用 ISO C 標準的時候，可以使用 __inline__ 關鍵字代替 inline 關鍵字

有幾種情況將不內嵌，而作爲普通函數調用：

1. 可變參數的函數
2. 調用 alloca 類庫的函數
3. 有可變尺寸數組聲明的函數
4. 非本地 goto 的函數
5. 嵌套調用的函數

const

1. 使用 const 限定符修飾形參可以防止函數修改傳入的參數
2. 使用 const 限定符修飾指針和引用

參考

1. cppreference