i**p
发帖数: 902 | 1 char s1[] = "Hello ";
char s2[] = "world";
char *s3;
s3 = strcat(s1, s2);
It is Ok. Both s1 and s3 will be "Hello world".
char *s1 = "Hello ";
char s2[] = "world";
char *s3;
s3 = strcat(s1, s2);
It is runtime error. Can you explain? |
P********e
发帖数: 2610 | 2 strcat(char*, const char*)
s1必须是char *;
char *s1 = "hello";
s1是指向 const char*的，因为s1是desti
【在 i**p 的大作中提到】
: char s1[] = "Hello ";
: char s2[] = "world";
: char *s3;
: s3 = strcat(s1, s2);
: It is Ok. Both s1 and s3 will be "Hello world".
: char *s1 = "Hello ";
: char s2[] = "world";
: char *s3;
: s3 = strcat(s1, s2);
: It is runtime error. Can you explain?
|
i**p
发帖数: 902 | 3 Do you mean
char *s1 = "hello"; s1 points to a const string?
【在 P********e 的大作中提到】
: strcat(char*, const char*)
: s1必须是char *;
: char *s1 = "hello";
: s1是指向 const char*的，因为s1是desti
|
P********e
发帖数: 2610 | 4 恩
【在 i**p 的大作中提到】
: Do you mean
: char *s1 = "hello"; s1 points to a const string?
|
d****2
发帖数: 6250 | 5 you totally mess up the memory. s1 must be allocated with enough space first
. |
i**p
发帖数: 902 | 6 How about
char s1[] = "hello";
I think the size of s1 has been set to 6. how does it work?
【在 P********e 的大作中提到】
: 恩
|
i**p
发帖数: 902 | 7 How does it work?
char s1[] = "Hello ";
char s2[] = "world";
char *s3;
s3 = strcat(s1, s2);
Both s1 and s3 will be "Hello world".
【在 i**p 的大作中提到】
: How about
: char s1[] = "hello";
: I think the size of s1 has been set to 6. how does it work?
|
d****2
发帖数: 6250 | 8
it does not work. any c programmer writes this way should be hanged.
【在 i**p 的大作中提到】
: How does it work?
: char s1[] = "Hello ";
: char s2[] = "world";
: char *s3;
: s3 = strcat(s1, s2);
: Both s1 and s3 will be "Hello world".
|
i**p
发帖数: 902 | 9 I run it by VC. It prints both s1 and s3 as "hello world".
【在 d****2 的大作中提到】
:
: it does not work. any c programmer writes this way should be hanged.
|
t****t
发帖数: 6806 | 10 运行结果正确不代表你的程序就是正确的
【在 i**p 的大作中提到】
: I run it by VC. It prints both s1 and s3 as "hello world".
|
|
|
i**p
发帖数: 902 | 11 then what tool can help us to find this programming error?
【在 t****t 的大作中提到】
: 运行结果正确不代表你的程序就是正确的
|
d****2
发帖数: 6250 | 12
that is a good research question. MSFT will be very interested to fix their
crappy code base.
【在 i**p 的大作中提到】
: then what tool can help us to find this programming error?
|
i**p
发帖数: 902 | 13 A good compiler should at least give a waring, but VC++ does not.
their
【在 d****2 的大作中提到】
:
: that is a good research question. MSFT will be very interested to fix their
: crappy code base.
|
d****2
发帖数: 6250 | 14
google buffer overflow.
【在 i**p 的大作中提到】
: A good compiler should at least give a waring, but VC++ does not.
:
: their
|
c*****t
发帖数: 1879 | 15 Just forget using strcat function. sprintf and strcpy are
less error prone.
【在 i**p 的大作中提到】
: A good compiler should at least give a waring, but VC++ does not.
:
: their
|
t****t
发帖数: 6806 | 16 name a compiler that will give a warning for this.
【在 i**p 的大作中提到】
: A good compiler should at least give a waring, but VC++ does not.
:
: their
|
m*****e
发帖数: 4193 | 17
It's not ok. You just got lucky.
【在 i**p 的大作中提到】
: A good compiler should at least give a waring, but VC++ does not.
:
: their
|
O*******d
发帖数: 20343 | 18 如果你把s1和s2中间插一个，看看能不能运行。再看一看_s1变成了什么。
char s1[] = "Hello ";
char _s1[] = "whatever";
char s2[] = "world";
char *s3;
s3 = strcat(s1, s2);
printf("s1 %s _s1 %s\n", s1, _s1);
【在 i**p 的大作中提到】
: I run it by VC. It prints both s1 and s3 as "hello world".
|
i**p
发帖数: 902 | 19 I know what all of you talk about. see my original post. My qustion is s1[]
and *s1 have different result, which means *s1 is more protective than s1[].
Why not make them the same?
char s1[] = "Hello ";
char *s1 = "Hello ";
【在 O*******d 的大作中提到】
: 如果你把s1和s2中间插一个，看看能不能运行。再看一看_s1变成了什么。
: char s1[] = "Hello ";
: char _s1[] = "whatever";
: char s2[] = "world";
: char *s3;
: s3 = strcat(s1, s2);
: printf("s1 %s _s1 %s\n", s1, _s1);
|
d****2
发帖数: 6250 | 20 char [] has space allocated on stack
char * is a pointer to static text area, write protected.
BTW, char [] and char * are different thing. Compiler does some translation
for you so you won't notice the difference most of time. Try sizeof(s1) in
both cases and you will know why. |
|
|
i**p
发帖数: 902 | 21 Of course, s1[] and *s1 are different. I have seen lots of programmer tried
to do something like “strcpy (s2, s1, sizeof(s1))” with s1 defined as *s1.
When is happened, I partly blame the programmer and mostly blame why C does
not do something to prevent this from the beginning or a latter improvement
. Anyway, this is a dangerous pitfall for a beginner and mostly to be an
interview question.
For the strcat(), it is much easier to generate a compiler warning or
runtime error for s1[] than *s1, b
【在 d****2 的大作中提到】
: char [] has space allocated on stack
: char * is a pointer to static text area, write protected.
: BTW, char [] and char * are different thing. Compiler does some translation
: for you so you won't notice the difference most of time. Try sizeof(s1) in
: both cases and you will know why.
|
t****t
发帖数: 6806 | 22 在你指责一个语言有这样那样的问题的时候, 有必要考虑语言设计时的历史环境. 为了
保持高速度, C语言里本来就没有数组边界检查, 更何况数组在函数调用里自动退化为指
针,数组尺寸信息早就没有了.
嫌C语言不安全的话,有很多更安全的语言可以用.就算是C++, 也有string class.
不过, 会在strcpy()里写上三个参数的, 可以想见你连门都没入. (FYI, 有三个参数的
那个叫做strncpy().) 门都没入的人还是虚心一点的好, 不要连纸上谈兵都谈不来,被人
笑掉大牙.
tried
s1.
does
improvement
an
【在 i**p 的大作中提到】
: Of course, s1[] and *s1 are different. I have seen lots of programmer tried
: to do something like “strcpy (s2, s1, sizeof(s1))” with s1 defined as *s1.
: When is happened, I partly blame the programmer and mostly blame why C does
: not do something to prevent this from the beginning or a latter improvement
: . Anyway, this is a dangerous pitfall for a beginner and mostly to be an
: interview question.
: For the strcat(), it is much easier to generate a compiler warning or
: runtime error for s1[] than *s1, b
|
d****2
发帖数: 6250 | 23 funny, OP is asking beginner questions yet acts like a pro wannabe. no wonder such forums are boring. compiler is harder than you think. |
i**p
发帖数: 902 | 24 小屁孩拣了个大包子，乐得找不到了北。老哥虽民工出身，码砖的事早就不干了。听说
过大博士不知道 １０００００００是负几吗？没听说过只能说你太嫩。我到是在民工
学徒其间老听到同道笑话师傅打字没他快，你也就和他有一比了。
为指
被人
【在 t****t 的大作中提到】
: 在你指责一个语言有这样那样的问题的时候, 有必要考虑语言设计时的历史环境. 为了
: 保持高速度, C语言里本来就没有数组边界检查, 更何况数组在函数调用里自动退化为指
: 针,数组尺寸信息早就没有了.
: 嫌C语言不安全的话,有很多更安全的语言可以用.就算是C++, 也有string class.
: 不过, 会在strcpy()里写上三个参数的, 可以想见你连门都没入. (FYI, 有三个参数的
: 那个叫做strncpy().) 门都没入的人还是虚心一点的好, 不要连纸上谈兵都谈不来,被人
: 笑掉大牙.
:
: tried
: s1.
|
m*****e
发帖数: 4193 | 25 Please take your troll somewhere else.
【在 i**p 的大作中提到】
: 小屁孩拣了个大包子，乐得找不到了北。老哥虽民工出身，码砖的事早就不干了。听说
: 过大博士不知道 １０００００００是负几吗？没听说过只能说你太嫩。我到是在民工
: 学徒其间老听到同道笑话师傅打字没他快，你也就和他有一比了。
:
: 为指
: 被人
|
t****t
发帖数: 6806 | 26 虽然不知道你说的是啥,不过常来的都知道,我不是靠写程序吃饭的
【在 i**p 的大作中提到】
: 小屁孩拣了个大包子，乐得找不到了北。老哥虽民工出身，码砖的事早就不干了。听说
: 过大博士不知道 １０００００００是负几吗？没听说过只能说你太嫩。我到是在民工
: 学徒其间老听到同道笑话师傅打字没他快，你也就和他有一比了。
:
: 为指
: 被人
|
n******t
发帖数: 4406 | 27 你真是小母牛选美啊。
【在 i**p 的大作中提到】
: 小屁孩拣了个大包子，乐得找不到了北。老哥虽民工出身，码砖的事早就不干了。听说
: 过大博士不知道 １０００００００是负几吗？没听说过只能说你太嫩。我到是在民工
: 学徒其间老听到同道笑话师傅打字没他快，你也就和他有一比了。
:
: 为指
: 被人
|
i**p
发帖数: 902 | 28 Please understand it is not shame to 靠写程序吃饭. My point is you pay more
attention to my example strcpy. Thank you anyway since you posted a lot for
this topic even though I do not agree most of your answer.
【在 t****t 的大作中提到】
: 虽然不知道你说的是啥,不过常来的都知道,我不是靠写程序吃饭的
|
f**y
发帖数: 138 | 29 You guys don't mention s2 at all? It probably will be "orld".
【在 i**p 的大作中提到】
: Please understand it is not shame to 靠写程序吃饭. My point is you pay more
: attention to my example strcpy. Thank you anyway since you posted a lot for
: this topic even though I do not agree most of your answer.
|
