通过索引访问char *的总线错误？！ [英] bus errors accessing a char * by index?!
问题描述
我似乎无法弄清楚为什么这段代码拒绝工作：
char * s =" hello";
printf（ "％s"，s [0]）;
i在运行时遇到总线错误。 whyyyyyy？
i在尝试strncpy等时也会遇到同样类型的错误。
请帮助。
i can''t seem to figure out why this code refuses to work:
char *s = "hello";
printf("%s", s[0]);
i keep getting bus errors when i run this. whyyyyyy?
i also get the same type of errors when trying to do strncpy and such.
please help.
推荐答案
在文章< 11 ********************** @ e3g2000cwe.googlegroups 。 com>，
< cr ******* @ gmail.comwrote：
In article <11**********************@e3g2000cwe.googlegroups. com>,
<cr*******@gmail.comwrote:
>我看上去不行弄清楚为什么这段代码拒绝工作：
char * s =" hello";
printf（"％s"，s [0]）;
<当我运行这个时，我不断收到总线错误。 whyyyyyy？
我在尝试strncpy等时也遇到了同样的错误。
请帮忙。
>i can''t seem to figure out why this code refuses to work:
char *s = "hello";
printf("%s", s[0]);
i keep getting bus errors when i run this. whyyyyyy?
i also get the same type of errors when trying to do strncpy and such.
please help.
听起来像是有缺陷的RAM芯片。你需要买一台新电脑。
Sounds like a defective RAM chip. You need to buy a new computer.
cr * ******@gmail.com 写道：
i似乎无法弄清楚为什么这段代码拒绝工作：
char * s =" hello";
printf（"％s"，s [0]）;
i can''t seem to figure out why this code refuses to work:
char *s = "hello";
printf("%s", s[0]);
您使用的是％s格式说明符，用于打印C
字符串，即指向空终止序列的指针chars。
s [0]，在你的例子中，是一个字符。
看到问题？
[提示：％c格式说明符有什么作用？]
You are using the %s format specifier, which is used to print a C
string, i.e. a pointer to a null terminated sequence of chars.
s[0], in your example, is a char.
See the problem?
[hint: what does the %c format specifier do?]
>
i当我遇到总线错误跑这个。 whyyyyyy？
i在尝试strncpy等时也会遇到同样类型的错误。
请帮忙。
>
i keep getting bus errors when i run this. whyyyyyy?
i also get the same type of errors when trying to do strncpy and such.
please help.
HTH，
--ag
-
Artie Gold - 奥斯汀，德克萨斯州
http://goldsays.blogspot.com
你不能亲吻*除非你想念**
[* - 保持简单，愚蠢。 ** - 简单，愚蠢。]
HTH,
--ag
--
Artie Gold -- Austin, Texas
http://goldsays.blogspot.com
"You can''t KISS* unless you MISS**"
[*-Keep it simple, stupid. **-Make it simple, stupid.]
char * s =" hello";
printf（"％s"，s [0]）;
i在运行时遇到总线错误。 whyyyyyy？
char *s = "hello";
printf("%s", s[0]);
i keep getting bus errors when i run this. whyyyyyy?
您可能想要这样做：
printf（"％s"，s）; / *打印整个字符串* /
或
printf（"％s"，& s [0]）; / *打印整个字符串;另一种说法是
同样的事情* /
或
printf（"％c"，s [0]）; / *只打印第一个字符。 * /
以下几行正在发生（虽然这是定义的实现
，所以可能不是这样）：
让我们说s存储在内存位置0x123456
我的版本1说''打印从内存位置开始的字符串
0x123456' '
我的版本2说''打印从内存位置开始的字符串
这是s''的第一个字符的地址（反过来，
0x123456，这很好。
我的版本3说''打印字符s [0]''''h''是
ascii 0x68。
现在这里是踢球者：
你的版本说''打印从内存位置开始的字符串
0x68。''但谁知道什么是0x68？可能是垃圾。或者更糟。
Michael
You probably want to do either:
printf("%s", s); /* print the whole string */
or
printf("%s", &s[0]); /* print the whole string; another way to say
the same thing */
or
printf("%c", s[0]); /* print just the first character. */
Something along the following lines is happening (although this is
implementation defined, so it may not be exactly this):
Let''s say s is stored at memory location 0x123456
My version 1 says ''print the string starting at memory location
0x123456''
My version 2 says ''print the string starting at the memory location
that is the address of the first character of s'' (which is, in turn,
0x123456, which is fine).
My version 3 says ''print the character s[0]'' which is ''h'' which is
ascii 0x68.
Now here''s the kicker:
Your version says ''print the string starting at memory location
0x68.'' But who knows what is at 0x68? Probably garbage. Or worse.
Michael
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