Google C++ 编程规范 1.3
Inline Functions
内联函数
▽Define functions inline only when they are small, say, 10 lines or less.
只有函数非常小，10行以内才定义为内联。
Definition: You can declare functions in a way that allows the compiler to expand them inline rather than calling them through the usual function call mechanism.
定义：一种函数调用机制，你将函数声明为内联，编译器会将整个函数体在调用处展开。
Pros: Inlining a function can generate more efficient object code, as long as the inlined function is small. Feel free to inline accessors and mutators, and other short, performance-critical functions.
前题条件：当内联一个很小函数时会产生更有效率的代码，考虑类成员访问函数或其他短小，性能要求严格的函数。
Cons: Overuse of inlining can actually make programs slower. Depending on a function's size, inlining it can cause the code size to increase or decrease. Inlining a very small accessor function will usually decrease code size while inlining a very large function can dramatically increase code size. On modern processors smaller code usually runs faster due to better use of the instruction cache.
限制：过度使用内联函数实际上会使减慢程序运行，取决于函数体大小，它决定了代码增加或减少。内联一个非常小成员访问函数会减少代码，而内联一个非常大的函数代码会戏剧性的增长。在现代处理器上由于广泛使用指令缓存，小代码通常会运行得更快。
Decision:
决策：
A decent rule of thumb is to not inline a function if it is more than 10 lines long. Beware of destructors, which are often longer than they appear because of implicit member- and base-destructor calls!
一个合适的经验法则：不要内联一个超过10行函数，但要小心析构函数，它并没有表面看上去那么小，因为它会调用类成员和基类的析构函数。 www.2cto.com
Another useful rule of thumb: it's typically not cost effective to inline functions with loops or switch statements (unless, in the common case, the loop or switch statement is never executed).
其他有用的经验法则：一个函数如果有判断或循环语句通常是没效率的。（除非在通常的情况下循环语句或判断语句不会执行）。
It is important to know that functions are not always inlined even if they are declared as such; for example, virtual and recursive functions are not normally inlined. Usually recursive functions should not be inline. The main reason for making a virtual function inline is to place its definition in the class, either for convenience or to document its behavior, e.g., for accessors and mutators.
知道哪些函数即使你声明了内联也不会内联很重要：比如说虚函数和递归函数在一般情况下不会内联。通常情况下递归函数不应内联。使虚函数内联的主要原因在于类定义，主要是方便的原因，比如说成员访问函数。
