字符串文字的类型 [英] Type of a string literal

问题描述

我听说字符串文字的类型为''char *''（即指向

a char对象的指针） ）。但我很困惑为什么这样做：


char * GetString（void）

{

return"你好;

}


int main（无效）

{

printf（" ％s \ n"，GetString（））;


返回0;

}


它打印''你好''。但是如果GetString（）返回的指针

指向一个本地对象，那么当

函数返回时，不会释放缓冲区，从而使指针指向没有？或者

是否意味着字符串文字的类型为''static char *''？或者更多

'，''static const char *''？


谢谢，

塞巴斯蒂安

解决方案

s0****@gmail.com 写道：

我听说字符串文字的类型为''char *''（即指向

a char对象的指针。但我很困惑为什么这样做：

字符串文字的字符数组为char，但它自动转换为
指向它在大多数情境下的第一个元素的指针，对于C中的所有数组类型都是常见的

char * GetString（void）

{

return" hello" ;;

}


int main （无效）

{

printf（"％s \ n"，GetString（））;


返回0 ;

}


它会打印''你好''。但是如果GetString（）返回的指针

指向一个本地对象，那么当

函数返回时，不会释放缓冲区，从而使指针指向没有？或者

是否意味着字符串文字的类型为''static char *''？或者更多

，''static const char *''？


谢谢，

Sebastian

源代码字符串文字放在静态数组中。它们的类型是char或wchar_t类型的
并且没有用const限定，但是修改

它们无论如何都会调用未定义的行为。

7月26日上午9:22，s0s ... @ gmail.com写道：

我听说字符串文字的类型为''char *''（即指向

a char对象的指针）。但我很困惑为什么这样做：


char * GetString（void）

{

return"你好;


}

见n1256.pdf中的6.4.5 p 5。字符串文字是不可变的，并且

被替换在TP 7中通过静态存储持续时间数组。它们实际的

类型是char [N]，其中N是sizeof返回的整数，或者是wchar_t

[N]（对于宽字符串文字）。

评估时，这些变为char *和wchar_t *。


请注意，GetString对程序员有用;返回值

无法修改！除非你记录下来，否则你的功能是误导的。

7月26日，5：03 * am，vipps ... @ gmail。 com写道：

7月26日上午9:22，s0s ... @ gmail.com写道：

您好，

我听说字符串文字的类型为''char *''（即指向

a char对象）。但我很困惑为什么这样做：

char * GetString（void）

{

* * return" hello" ;;

}

见n1256.pdf中的6.4.5 p 5。字符串文字是不可变的，并且

被替换在TP 7中通过静态存储持续时间数组。它们实际的

类型是char [N]，其中N是sizeof返回的整数，或者是wchar_t

[N]（对于宽字符串文字）。

评估时，这些变为char *和wchar_t *。


请注意，GetString对程序员有用;返回值

无法修改！除非你记录下来，否则你的功能是误导的。
误导。

谢谢。至于最后一部分：用'const'来限定

函数定义是不错的做法？

Hi,

I''ve heard that a string literal has type ''char *'' (i.e., a pointer to
a char object). But I''m confused as to why this works:

char *GetString(void)
{
return "hello";
}

int main(void)
{
printf("%s\n", GetString());

return 0;
}

And it does print ''hello''. But if the pointer that GetString() returns
points to a local object, wouldn''t the buffer be deallocated when the
function returns, thus making the pointer point to nothing? Or does
that mean that a string literal has type ''static char *''? Or more
precisely, ''static const char *''?

Thanks,
Sebastian

解决方案

s0****@gmail.com wrote:

Hi,

I''ve heard that a string literal has type ''char *'' (i.e., a pointer to
a char object). But I''m confused as to why this works:

A string literal has type array of char, but it automatically is
converted to a pointer to it''s first element under most contexts, as is
common for all array types in C.

char *GetString(void)
{
return "hello";
}

int main(void)
{
printf("%s\n", GetString());

return 0;
}

And it does print ''hello''. But if the pointer that GetString() returns
points to a local object, wouldn''t the buffer be deallocated when the
function returns, thus making the pointer point to nothing? Or does
that mean that a string literal has type ''static char *''? Or more
precisely, ''static const char *''?

Thanks,
Sebastian

Source code string literals are placed in static arrays. Their type is
of type char or wchar_t and are not qualified with const, but modifying
them invokes undefined behaviour anyway.

On Jul 26, 9:22 am, [e-mail] wrote:

Hi,

I''ve heard that a string literal has type ''char *'' (i.e., a pointer to
a char object). But I''m confused as to why this works:

char *GetString(void)
{
return "hello";

}

See 6.4.5 p 5 from n1256.pdf. string literals are immutable and
"replaced" in TP 7 by static storage duration arrays. Their actual
type is char [N] where N is the integer returned by sizeof, or wchar_t
[N] (for wide string literals).
When evaluated, these become char * and wchar_t *.

Notice that GetString lies to the programmer; the returned value
cannot be modified! Unless you document that, your function is
misleading.

On Jul 26, 5:03*am, [e-mail] wrote:

On Jul 26, 9:22 am, [e-mail] wrote:

Hi,

I''ve heard that a string literal has type ''char *'' (i.e., a pointer to
a char object). But I''m confused as to why this works:

char *GetString(void)
{
* * return "hello";

}

See 6.4.5 p 5 from n1256.pdf. string literals are immutable and
"replaced" in TP 7 by static storage duration arrays. Their actual
type is char [N] where N is the integer returned by sizeof, or wchar_t
[N] (for wide string literals).
When evaluated, these become char * and wchar_t *.

Notice that GetString lies to the programmer; the returned value
cannot be modified! Unless you document that, your function is
misleading.

Thanks. As for the last part: would it be good practice to qualify the
function definition with ''const''?

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