虽然这个问题是关于整数的，但值得注意的是，如果需要常量结构或字符串，#define和enum是无用的。它们通常都作为指针传递给函数。(对于字符串，它是必需的;有了结构，效率就高多了。)

As for integers, if you're in an embedded environment with very limited memory, you might need to worry about where the constant is stored and how accesses to it are compiled. The compiler might add two consts at run time, but add two #defines at compile time. A #define constant may be converted into one or more MOV [immediate] instructions, which means the constant is effectively stored in program memory. A const constant will be stored in the .const section in data memory. In systems with a Harvard architecture, there could be differences in performance and memory usage, although they'd likely be small. They might matter for hard-core optimization of inner loops.

的定义

const int const_value = 5;

并不总是定义一个常数值。一些编译器(例如tcc 0.9.26)只分配名称为“const_value”的内存。使用标识符“const_value”你不能修改这个内存。但是你仍然可以使用另一个标识符来修改内存:

const int const_value = 5;
int *mutable_value = (int*) &const_value;
*mutable_value = 3;
printf("%i", const_value); // The output may be 5 or 3, depending on the compiler.

这意味着定义

#define CONST_VALUE 5

是定义一个不能用任何方法修改的常数值的唯一方法。

一般来说:

static const

因为它尊重作用域并且是类型安全的。

我能看到的唯一警告是:如果您希望变量可能在命令行上定义。还有另一种选择:

#ifdef VAR // Very bad name, not long enough, too general, etc..
  static int const var = VAR;
#else
  static int const var = 5; // default value
#endif

尽可能使用类型安全的替代方法，而不是宏/省略号。

如果你真的需要使用宏(例如，你想要__FILE__或__LINE__)，那么你最好非常小心地命名你的宏:在它的命名约定中，Boost推荐所有大写字母，以项目的名称(这里是BOOST_)开头，而仔细阅读库，你会注意到这(通常)后面是特定区域(库)的名称，然后是一个有意义的名称。

它通常会产生很长的名字:)

这取决于你需要这个值做什么。你(和目前所有人一样)忽略了第三种选择:

Static const int var = 5; #定义var 5 枚举{var = 5};

忽略名字的选择问题，那么:

If you need to pass a pointer around, you must use (1). Since (2) is apparently an option, you don't need to pass pointers around. Both (1) and (3) have a symbol in the debugger's symbol table - that makes debugging easier. It is more likely that (2) will not have a symbol, leaving you wondering what it is. (1) cannot be used as a dimension for arrays at global scope; both (2) and (3) can. (1) cannot be used as a dimension for static arrays at function scope; both (2) and (3) can. Under C99, all of these can be used for local arrays. Technically, using (1) would imply the use of a VLA (variable-length array), though the dimension referenced by 'var' would of course be fixed at size 5. (1) cannot be used in places like switch statements; both (2) and (3) can. (1) cannot be used to initialize static variables; both (2) and (3) can. (2) can change code that you didn't want changed because it is used by the preprocessor; both (1) and (3) will not have unexpected side-effects like that. You can detect whether (2) has been set in the preprocessor; neither (1) nor (3) allows that.

因此，在大多数情况下，优先选择“enum”而不是其他选项。否则，第一个和最后一个要点很可能是控制因素——如果你需要同时满足这两个点，你必须更努力地思考。

如果你问的是c++，那么你每次都应该使用option (1) - static const。

静态const和#define之间的区别在于前者使用内存，而后者不使用内存进行存储。其次，您不能传递#define对象的地址，而可以传递静态const对象的地址。实际上，这取决于我们所处的环境，我们需要在这两者中选择一个。两者在不同的情况下都处于最佳状态。请不要认为一个比另一个好。: -)

如果是这样的话，丹尼斯·里奇会把最好的留下来……哈哈哈……: -)

C中const的另一个缺点是不能在初始化另一个const时使用该值。

static int const NUMBER_OF_FINGERS_PER_HAND = 5;
static int const NUMBER_OF_HANDS = 2;

// initializer element is not constant, this does not work.
static int const NUMBER_OF_FINGERS = NUMBER_OF_FINGERS_PER_HAND 
                                     * NUMBER_OF_HANDS;

即使这对const也不起作用，因为编译器不会将其视为常量:

static uint8_t const ARRAY_SIZE = 16;
static int8_t const lookup_table[ARRAY_SIZE] = {
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}; // ARRAY_SIZE not a constant!

我很乐意在这些情况下使用类型化的const，否则…