评论：我的C FAQ页面 [英] Review: My C FAQ Page
问题描述
您好c.l.c.
我认为现在是时候提起它了。在过去的2-3个月里，
我一直在努力建立我的C常见问题解答页面，其中包含大约
40 C的问题。很少有人从c.l.c.采用。
同一页面有3个Linux问题，可以忽略。
也是其他几个部分，这里有点OT，并且可以
也被忽略。
（天啊！火焰会倒进......）
-
Vijay Kumar R Zanvar
C常见问题解答 - http://www.geocities.com/vijoeyz/faq/
Vijay Kumar R Zanvar写道：我认为是时候了我提出来了。在过去的2-3个月里，我一直在努力构建我的C FAQ页面，其中包含40个问题。很少有人从c.l.c.采用。
同一页面有3个Linux问题，可以忽略。还有很少的其他部分，这里有点OT，也可以忽略。
不幸的是很大比例您页面上的信息是误导或错误的
。以下是两个例子：
[关于 http://www.geocities.com/vijoeyz/faq/c/struct_cmp.txt]
使用memcmp（）比较结构是一个坏主意，因为
"当一个值存储在结构或联合类型的对象中时，
包括在一个成员对象中，该对象的字节为
表示与任何填充字节对应的
未指定的值。 [6.2.6.1]
这意味着memcmp可能表明两个结构不是
相等，即使它们根据成员相等
比较。换句话说，以下内容可能会打印false：
struct {int a; char b; } a = {3,2}，b = a;
if（memcmp（& a，& b，sizeof a）== 0）
puts（ " true"）;
else
puts（" false"）;
[关于 http://www.geocities.com/vijoeyz/faq/c/sizeof_impl.txt ，
其中宏
#define sizeof_type（类型）（size_t）（（类型*）0 + 1）
出现]
这会调用未定义的行为：空指针上的指针算术
未定义。即使算术保证有效，从指针到整数的转换也是实现定义的，并且可能不会给出你期望的结果。
Jeremy。
Vijay Kumar R Zanvar写道：
（哦，天啊！火焰会倒in ...）
现实的态度很好。
这一个
http://www.geocities.com/vijoeyz/faq/knr/1 /swap.txt
与峰会的对面常见问题解答：
第一次交换有多个副作用且
其他两个交换，对于签名的ineger类型有溢出问题。
http://www.eskimo.com/~scs/C-faq/q10.3.html
-
pete
Em周五，2004年2月6日16:17:08 +0530，Vijay Kumar R Zanvar escreveu：
你好clc
你好。
Vijay Kumar R Zanvar
C常见问题解答 - http：/ /www.geocities.com/vijoeyz/faq/
尽管NG中的其他地方出现了问题，但我还是喜欢DMR对
你的一个问题...
-
Quidquid latine dictum sit altum viditur
Hi c.l.c.
I think it''s time that I bring it up. Over the last 2-3 months,
I have been trying to build my C FAQ page which has around
40 C questions. Few of them have been adopted from c.l.c. The
same page has 3 Linux questions, and can be ignored. There
are few other sections, too, which are are a little OT here, and can
also be ignored.
(Oh My God! Flames are gonna pour in...)
--
Vijay Kumar R Zanvar
C FAQs - http://www.geocities.com/vijoeyz/faq/
Vijay Kumar R Zanvar wrote:I think it''s time that I bring it up. Over the last 2-3 months,
I have been trying to build my C FAQ page which has around
40 C questions. Few of them have been adopted from c.l.c. The
same page has 3 Linux questions, and can be ignored. There
are few other sections, too, which are are a little OT here, and can
also be ignored.
Unfortunately a large proportion of the information on your page is
misleading or simply wrong. Here are two examples:
[Regarding http://www.geocities.com/vijoeyz/faq/c/struct_cmp.txt]
Using memcmp() to compare structures is a bad idea, because
"When a value is stored in an object of structure or union type,
including in a member object, the bytes of the object
representation that correspond to any padding bytes take
unspecified values." [6.2.6.1]
This means that memcmp may indicate that two structures are not
"equal", even though they are equal according to a memberwise
comparison. In other words, the following may print "false":
struct { int a; char b; } a = { 3, 2 }, b = a;
if (memcmp(&a, &b, sizeof a) == 0)
puts("true");
else
puts("false");
[Regarding http://www.geocities.com/vijoeyz/faq/c/sizeof_impl.txt,
where the macro
#define sizeof_type( type ) (size_t)((type*)0 + 1 )
appears]
This invokes undefined behaviour: pointer arithmetic on null pointers
is not defined. Even if the arithmetic were guaranteed to work, the
conversion from pointer to integer is implementation-defined and may
not give the results you expect.
Jeremy.
Vijay Kumar R Zanvar wrote:
(Oh My God! Flames are gonna pour in...)
A realistic attitude is good.
This one
http://www.geocities.com/vijoeyz/faq/knr/1/swap.txt
is the opposite of Summits FAQ:
The first swap has unsequenced multiple side-effects and the
other two swaps, have overflow problems for signed ineger types.
http://www.eskimo.com/~scs/C-faq/q10.3.html
--
pete
Em Fri, 06 Feb 2004 16:17:08 +0530, Vijay Kumar R Zanvar escreveu:
Hi c.l.c.
Hi.
Vijay Kumar R Zanvar
C FAQs - http://www.geocities.com/vijoeyz/faq/
Despite the problems pointed elsewhere in this NG, I liked DMR''s answer to
your One Question...
--
Quidquid latine dictum sit altum viditur
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