Thread: Confusing pointers, Prints wierd result

Hi All,

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

//First funtion
void func(char *p)
{
      p = "Hello";  // Statement 1
}

int main()
{
 
 char *p = NULL;
 func(&p,&c);
 printf("Val of p:%s\n",p);
 
}

Alternative function declaration: //Function 2

Code:

void func(char **p)
{
    
    *p = "Hello";         // Statement 2
    
}

What is confusing to me is the outputs:

With the function declared as in Function 1:
<NULL>

With the function declared as in Function 2:
Hello

Doubts:
1. How come Statement 1 is valid?
2. Will address be assigned to the pointer variable p in Statement 1?
3. What is the difference b/w *p="Hello" and p="Hello"?
4. how is that by calling Function 2 instead of Function 1 it prints Hello?


Thanks in advance

Thanks for your time...

1. How come Statement 1 is valid?
2. Will address be assigned to the pointer variable p in Statement 1?
3. What is the difference b/w *p="Hello" and p="Hello"?


More doubts follow

Code:

int main()
{
 
 char *p = NULL;
 func(&p,&c);
 printf("Val of p:%s\n",p);
}

Function 3
void func(char **p)
{
    char *q = "test"
    *p = &q;         // Statement 3
    
}

Ouput :
Test

What my doubts are while introducing Function 3:

1. Now that i have declared char *q which is local to the Function, how come output is "test"?
2. Is this dangling pointer? As the memory location is cleared once the function comes out?

Thanks..

1. How come Statement 1 is valid?

Why wouldn't it be? You're creating a local variable char *p, and setting it to point to the address of string "Hello" in static storage. Function exits and local variable p is destroyed. Sounds valid. The value of p in main() remains untouched.

2. Will address be assigned to the pointer variable p in Statement 1?

Yes. To the address of "Hello" in static storage.

1. Now that i have declared char *q which is local to the Function, how come output is "test"?

All string literals (e.g. everything inside double quotes) persist for the duration of the program.

2. Is this dangling pointer? As the memory location is cleared once the function comes out?

See above.