使用do {...} while（0） [英] use of do{...}while(0)
问题描述
上述做什么用途。这只是一个样式问题。
由于上述相同条件将应用do-while（0）;
因为循环只执行一次。我经历了faq部分10.4
但我很少被人理解。请问有什么答案吗？
-
组合是国际象棋的核心
A.Alekhine
邮寄地址：
sathyashrayan at gmail DOT com
What is the use of the above do-while. Is it simply a style issue.
Since the above same condition will applied with out a do-while(0);
because the loop executes only once. I went through the faq section 10.4
but I am little understood. Any answers please?
--
"combination is the heart of chess"
A.Alekhine
Mail to:
sathyashrayan AT gmail DOT com
推荐答案
sathyashrayan <螺**************** @ nomail.com>潦草地写着以下内容：
sathyashrayan <lo****************@nomail.com> scribbled the following:
上述do-while有什么用处。它只是一个样式问题。
由于上述相同的条件将应用do-while（0）;
因为循环只执行一次。我经历了常见问题10.4节，但我很少被人理解。请问有什么答案吗？
What is the use of the above do-while. Is it simply a style issue.
Since the above same condition will applied with out a do-while(0);
because the loop executes only once. I went through the faq section 10.4
but I am little understood. Any answers please?
这是一个聪明的方法，使多语句宏看起来像
函数。
考虑：
#define DO_MAGIC_STUFF（x）{foo（x）; bar（x）;}
if（willDoMagic）
DO_MAGIC_STUFF（quux）;
else
printf（ 不会做神奇的东西！\ n;）;
这不会编译（练习：为什么？）。但是，将定义
更改为：
#define DO_MAGIC_STUFF（x）do {foo（x）; bar（x）;} while（0）
它会编译（练习：为什么？）。
-
/ - Joona Palaste（pa*****@cc.helsinki.fi）-------------芬兰-------- \
\ ------------------------------------------ --------------规则！ -------- /
我希望我们认识的人会死，所以我们可以给他们留下鲜花。
- 一个6岁的孩子女孩，在墓地里看到鲜花
It''s a clever way to make a multi-statement macro appear to work like a
function.
Consider:
#define DO_MAGIC_STUFF(x) {foo(x); bar(x);}
if (willDoMagic)
DO_MAGIC_STUFF(quux);
else
printf("Won''t do magic stuff!\n");
This won''t compile (exercise: why?). However, change the definition
to:
#define DO_MAGIC_STUFF(x) do {foo(x); bar(x);} while (0)
and it will compile (exercise: why?).
--
/-- Joona Palaste (pa*****@cc.helsinki.fi) ------------- Finland --------\
\-------------------------------------------------------- rules! --------/
"I wish someone we knew would die so we could leave them flowers."
- A 6-year-old girl, upon seeing flowers in a cemetery
sathyashrayan写道：
sathyashrayan wrote:
上面做什么用途。它只是一个样式问题。
由于上述相同的条件将应用do-while（0）;
因为循环只执行一次。我经历了常见问题10.4节，但我很少被人理解。请问有什么答案吗？
What is the use of the above do-while. Is it simply a style issue.
Since the above same condition will applied with out a do-while(0);
because the loop executes only once. I went through the faq section 10.4
but I am little understood. Any answers please?
10.4的答案文本可能是一个很好的解释，如果您了解上下文，则需要b / b
。它是关于编写一个C语言宏，
有效地扩展到几个独立的C语句中。
只是在心理上思考做什么{... } while（0）包装器正在做，你会看到
看看技巧是怎么回事工作。
- Larry Weiss
The answer text at 10.4 is probably about as good an explanation as is needed
if you understand the context. It''s about writing a C language macro that
expands effectively into several standalone C statements.
Just mentally think about what the do{...}while(0) wrapper is doing and you''ll
see how the "trick" works.
- Larry Weiss
2005年1月26日星期三15:16:16 +0000，Joona I Palaste写道：
On Wed, 26 Jan 2005 15:16:16 +0000, Joona I Palaste wrote:
sathyashrayan< lo **************** @ nomail.com>潦草地写着以下内容：
sathyashrayan <lo****************@nomail.com> scribbled the following:
上述do-while有什么用处。它只是一个样式问题。
由于上述相同的条件将应用do-while（0）;
因为循环只执行一次。我经历了常见问题10.4节，但我很少被人理解。请问有什么答案吗？
这是一个聪明的方法，使多语句宏看起来像
函数。
What is the use of the above do-while. Is it simply a style issue.
Since the above same condition will applied with out a do-while(0);
because the loop executes only once. I went through the faq section 10.4
but I am little understood. Any answers please?
It''s a clever way to make a multi-statement macro appear to work like a
function.
不是这样的功能，一个声明要求;最后以
完成它。
考虑：
#define DO_MAGIC_STUFF（x）{foo（x）; bar（x）;} if（willDoMagic）
DO_MAGIC_STUFF（quux）;
你是对的，虽然它很可能出现在类似函数的
宏中。
else
printf（不要做魔术！\ n）;
这不会编译（练习：为什么？）。但是，将定义更改为：
#define DO_MAGIC_STUFF（x）do {foo（x）; bar（x）;} while（0）
它会编译（练习：为什么？）。
Not a function as such, a single statement requiring a ; at the end to
complete it.
Consider:
#define DO_MAGIC_STUFF(x) {foo(x); bar(x);} if (willDoMagic)
DO_MAGIC_STUFF(quux);
You''re right though that it is very likely to appear in a function-like
macro.
else
printf("Won''t do magic stuff!\n");
This won''t compile (exercise: why?). However, change the definition to:
#define DO_MAGIC_STUFF(x) do {foo(x); bar(x);} while (0)
and it will compile (exercise: why?).
并且有一个我的回复中有很大的线索。 :-)
劳伦斯
And there''s a big clue in my reply. :-)
Lawrence
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