char *按值传递 [英] char * pass-by-value

问题描述

抱歉新手问题;阅读常见问题后，我仍然离开

想知道这是否合法：


void strip（char * in）

{

in [strlen（in）-1] =''\ 0'';

返回;

}


我认为是这样，因为变量''in''的内存位置是正确传递的，所以strlen（）函数寻找''\\ \\ 0''

获得其值的字符。这是真的吗？


谢谢，


Andrej

解决方案

< blockquote> Andrej Prsa写道：

抱歉新手问题;在阅读常见问题解答后，我仍然离开
想知道这是否合法：

void strip（char * in）
{
in [strlen（in） - 1] =''\ 0'';
返回;
}
我认为是，因为变量''in''的内存位置是字符来获取它的值。这是真的吗？

是的，这是完全合法的，是的，这就是strlen的工作方式。


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====================================== ============ =============

Andrej Prsa写道：

抱歉新手问题;在阅读常见问题解答后，我仍然离开
想知道这是否合法：

void strip（char * in）
{
in [strlen（in） - 1] =''\ 0'';
返回;
}
我认为是，因为变量''in''的内存位置是字符来获取它的值。这是真的吗？

谢谢，

Andrej

void strip2（char in []）

{

in [strlen（in）-1] =''\ 0'';

return;

}


与

相同
void strip1（char * in）

{

*（in + strlen（in）-1）=''\''';

返回;

}

NB

char * s与char s []不等同，如下所示：


char string [32] =" litte string" ;;

char * ptr = string;

sizeof（string）==> 32

sizeof（ptr）==> 4 / *（在一个4字节指针的机器上）* /

NB
$ strite（in）-1中的
因为减法而不是很好...

用指针减去是不是很有意义......

在这种情况下它就像（在+（strlen（in）-1））


xavier

Andrej Prsa写道：

抱歉新手问题;在阅读常见问题解答后，我仍然离开
想知道这是否合法：

void strip（char * in）
{
in [strlen（in） - 1] =''\ 0'';
返回;
}
我认为是，因为变量''in''的内存位置是字符来获取它的值。这是真的吗？

字符串`in`最好至少包含一个字符，或者`in`

必须指向一个字符（或更多）字符存入合法存储。因为

strlen（in）== 0意味着你有`in [-1] = 0`。


BOOM今天 - 如果你是幸运。否则，BOOM明天。


-

Chris理解是一把三刃剑 Dollin

Hi,

sorry for the newbie question; after reading the FAQ, I am still left
wondering if this is legal:

void strip (char *in)
{
in[strlen(in)-1] = ''\0'';
return;
}

I figure it is, because the memory location of the variable ''in'' is
passed properly and I guess that the strlen() function seeks the ''\0''
character to obtain its value. Is this true?

Thanks,

Andrej

解决方案

Andrej Prsa wrote:

Hi,

sorry for the newbie question; after reading the FAQ, I am still left
wondering if this is legal:

void strip (char *in)
{
in[strlen(in)-1] = ''\0'';
return;
}

I figure it is, because the memory location of the variable ''in'' is
passed properly and I guess that the strlen() function seeks the ''\0''
character to obtain its value. Is this true?

Yes, it''s perfectly legal, and yes, that''s how strlen works.

--
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In an attempt to reduce ''unwanted noise'' on the ''signal'' ...

Disclaimer:

Any comment/code I contribute might =NOT= be 100% portable, nor
semantically correct [read - ''not 100% pedantically correct''].
I don''t care too much about that though, and I reckon it''s the
same with most ''visitors'' here. However, rest assured that any
''essential'' (?) corrections WILL almost certainly appear v.soon
[read - ''to add noise as they see fit, *a pedant* will be along
shortly''].

WARNINGS: Always read the label. No beside-the-point minutiae
filter supplied. Keep away from children. Do not ignite.
================================================== =============

Andrej Prsa wrote:

Hi,

sorry for the newbie question; after reading the FAQ, I am still left
wondering if this is legal:

void strip (char *in)
{
in[strlen(in)-1] = ''\0'';
return;
}

I figure it is, because the memory location of the variable ''in'' is
passed properly and I guess that the strlen() function seeks the ''\0''
character to obtain its value. Is this true?

Thanks,

Andrej

void strip2 (char in[])
{
in[strlen(in)-1] = ''\0'';
return;
}

same as

void strip1 (char *in)
{
*(in+strlen(in)-1) = ''\0'';
return;
}
N.B.
char * s is not equivalent to char s[] as you can see with the following :

char string[32] = "litte string";
char *ptr = string;
sizeof (string) ==> 32
sizeof (ptr) ==> 4 /* (on a machine with 4 byte pointers) */
N.B.
in+strlen(in)-1 is not very nice because of the substract ...
it''s not very meaningfull to substract with pointers ...
in this case it''s like (in + (strlen(in)-1))

xavier

Andrej Prsa wrote:

Hi,

sorry for the newbie question; after reading the FAQ, I am still left
wondering if this is legal:

void strip (char *in)
{
in[strlen(in)-1] = ''\0'';
return;
}

I figure it is, because the memory location of the variable ''in'' is
passed properly and I guess that the strlen() function seeks the ''\0''
character to obtain its value. Is this true?

The string `in` had better have at least one character in it, or `in`
must point one (or more) character(s) into legal storage. Because
strlen(in) == 0 would mean you had `in[-1]=0`.

BOOM today - if you''re lucky. Otherwise, BOOM tomorrow.

--
Chris "understanding is a three-edged sword" Dollin

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