See the Forum on the discussion of this issue, the feeling is also involved in a relatively broad, and many people have made this mistake, such as declaring char *p = "Hello world!"; I tried to change the string content with the P pointer, so I summed up the question. The reprint indicates the author Logic0 and the source. Main analytic issues: Issue 1:
#include "stdio.h"
Char *get_string_1 ()
{
Char p[] = "Hello world!";
return p;
}
Char *get_string_2 ()
{
char *p = "Hello world!";
return p;
}
int main ()
{
Char *p;
p = get_string_1 ();
printf ("get_string_1:%s\n", p);
p = get_string_2 ();
printf ("get_string_2:%s\n", p);
return 0;
}
Output:
Get_string_1: (garbled or no output), Linux does not have any output
Get_string_2:hello world!
Why is that? Question 2:
char *p = "Hello world!"; It is not possible to write this in the actual application. Question 3:
char *p = "Hello world!"; with char p[]= "Hello world!"; What is the difference between the details and the operation. Analytical:
char *p = "Hello world!"; With char p[] = "Hello world!"; Both are used to declare a string and initialize it to Hello world!, but the meaning of the expression is very different.
From the object it declares:
Char p[] = "Hello world!"; Used to declare an array p with an array size of 12 bytes.
char *p = "Hello world!"; Used to declare a pointer p, pointing to "Hello world!" The starting position of the string.
From the storage location:
Char p[] = "Hello world!"; The p array is stored as a local variable in the stack area;
char *p = "Hello world!"; In this statement, "Hello world!" is stored in the static data area, and is global, p is just a pointer to this area. If you don't believe it, you can try the code below to see if it's the same address:
char *p1 = "Hello world!";
char *p2 = "Hello world!";
printf ("p1:%x\np2:%x\n", P1,P2);
From the completion of the function after the work to see:
c function after the execution of the stack area cleanup operations, the static data area and the heap is not, so the first problem is not difficult to explain, the get_string_1 () function after the release of the stack memory, so there is no "Hello world!" When declaring the memory, it is impossible to output. Well, write char *p = "Hello world!"; How does it fit? Can you write like this?
This is a historical issue, before the Const keyword was introduced in C, it is legal, and there is a long period of time, a lot of code in this period, the use of this notation, the new version of C language for compatibility, it is allowed to write, but it is best not to do so, because this writing will eventually be eliminated, Perhaps one day your code with a new version of the compiler, and then inexplicable problem, to find this bug is not an easy thing to estimate. Now it's best to write:
const char *p = "Hello world!";
Or
Char p[] = "Hello world!";
What difference do they have in the operation and the details?
A lot of difference, because I caishuxueqian, only summed up the following points, forget to add:
1. Char *p = "Hello world!"; Can be operated with p++, sizeof (p) = = 4;
2.char p[]= "Hello world!"; sizeof (P) = = 12; See the Forum on the discussion of this issue, the feeling is also involved in a relatively broad, and many people have made this mistake, such as declaring char *p = "Hello world!"; I tried to change the string content with the P pointer, so I summed up the question. The reprint indicates the author Logic0 and the source. Main analytic issues: Issue 1:
#include "stdio.h"
Char *get_string_1 ()
{
Char p[] = "Hello world!";
return p;
}
Char *get_string_2 ()
{
char *p = "Hello world!";
return p;
}
int main ()
{
Char *p;
p = get_string_1 ();
printf ("get_string_1:%s\n", p);
p = get_string_2 ();
printf ("get_string_2:%s\n", p);
return 0;
}
Output:
Get_string_1: (garbled or no output), Linux does not have any output
Get_string_2:hello world!
Why is that? Question 2:
char *p = "Hello world!"; It is not possible to write this in the actual application. Question 3:
char *p = "Hello world!"; with char p[]= "Hello world!"; What is the difference between the details and the operation. Analytical:
char *p = "Hello world!"; With char p[] = "Hello world!"; Both are used to declare a string and initialize it to Hello world!, but the meaning of the expression is very different.
From the object it declares:
Char p[] = "Hello world!"; Used to declare an array p with an array size of 12 bytes.
char *p = "Hello world!"; Used to declare a pointer p, pointing to "Hello world!" The starting position of the string.
From the storage location:
Char p[] = "Hello world!"; The p array is stored as a local variable in the stack area;
char *p = "Hello world!"; In this statement, "Hello world!" is stored in the static data area, and is global, p is just a pointer to this area. If you don't believe it, you can try the code below to see if it's the same address:
char *p1 = "Hello world!";
char *p2 = "Hello world!";
printf ("p1:%x\np2:%x\n", P1,P2);
From the completion of the function after the work to see:
c function after the execution of the stack area cleanup operations, the static data area and the heap is not, so the first problem is not difficult to explain, the get_string_1 () function after the release of the stack memory, so there is no "Hello world!" When declaring the memory, it is impossible to output. Well, write char *p = "Hello world!"; How does it fit? Can you write like this?
This is a historical issue, before the Const keyword was introduced in C, it is legal, and there is a long period of time, a lot of code in this period, the use of this notation, the new version of C language for compatibility, it is allowed to write, but it is best not to do so, because this writing will eventually be eliminated, Perhaps one day your code with a new version of the compiler, and then inexplicable problem, to find this bug is not an easy thing to estimate. Now it's best to write:
const char *p = "Hello world!";
Or
Char p[] = "Hello world!";
What difference do they have in the operation and the details?
A lot of difference, because I caishuxueqian, only summed up the following points, forget to add:
1. Char *p = "Hello world!"; Can be operated with p++, sizeof (p) = = 4;
2.char p[]= "Hello world!"; sizeof (P) = = 12; See the Forum on the discussion of this issue, the feeling is also involved in a relatively broad, and many people have made this mistake, such as declaring char *p = "Hello world!"; I tried to change the string content with the P pointer, so I summed up the question. The reprint indicates the author Logic0 and the source. Main analytic issues: Issue 1:
#include "stdio.h"
Char *get_string_1 ()
{
Char p[] = "Hello world!";
return p;
}
Char *get_string_2 ()
{
char *p = "Hello world!";
return p;
}
int main ()
{
Char *p;
p = get_string_1 ();
printf ("get_string_1:%s\n", p);
p = get_string_2 ();
printf ("get_string_2:%s\n", p);
return 0;
}
Output:
Get_string_1: (garbled or no output), Linux does not have any output
Get_string_2:hello world!
Why is that? Question 2:
char *p = "Hello world!"; It is not possible to write this in the actual application. Question 3:
char *p = "Hello world!"; with char p[]= "Hello world!"; What is the difference between the details and the operation. Analytical:
char *p = "Hello world!"; With char p[] = "Hello world!"; Both are used to declare a string and initialize it to Hello world!, but the meaning of the expression is very different.
From the object it declares:
Char p[] = "Hello world!"; Used to declare an array p with an array size of 12 bytes.
char *p = "Hello world!"; Used to declare a pointer p, pointing to "Hello world!" The starting position of the string.
From the storage location:
Char p[] = "Hello world!"; The p array is stored as a local variable in the stack area;
char *p = "Hello world!"; In this statement, "Hello world!" is stored in the static data area, and is global, p is just a pointer to this area. If you don't believe it, you can try the code below to see if it's the same address:
char *p1 = "Hello world!";
char *p2 = "Hello world!";
printf ("p1:%x\np2:%x\n", P1,P2);
From the completion of the function after the work to see:
c function after the execution of the stack area cleanup operations, the static data area and the heap is not, so the first problem is not difficult to explain, the get_string_1 () function after the release of the stack memory, so there is no "Hello world!" When declaring the memory, it is impossible to output. Well, write char *p = "Hello world!"; How does it fit? Can you write like this?
This is a historical issue, before the Const keyword was introduced in C, it is legal, and there is a long period of time, a lot of code in this period, the use of this notation, the new version of C language for compatibility, it is allowed to write, but it is best not to do so, because this writing will eventually be eliminated, Perhaps one day your code with a new version of the compiler, and then inexplicable problem, to find this bug is not an easy thing to estimate. Now it's best to write:
const char *p = "Hello world!";
Or
Char p[] = "Hello world!";
What difference do they have in the operation and the details?
A lot of difference, because I caishuxueqian, only summed up the following points, forget to add:
1. Char *p = "Hello world!"; Can be operated with p++, sizeof (p) = = 4;
2.char p[]= "Hello world!"; sizeof (P) = = 12;
(go) parse char *p and char[]
