Constant Pointer

Question

Please tell me about all the variations of these above types of questions that can be asked?

Comments

https://www.geeksforgeeks.org/const-qualifier-in-c/

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it will give error

preincrement or post increment operator will not work on constant pointer

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@srestha , could u please tell me ,what should be output for this code :-

#include<stdio.h>
int main()
{
   const int *p =(int*) 10;
  printf("%d",(*p));
}

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p is not initialized. I guess the garbage value that p has will be treated as address and the program will try to store 10 there which will result in an error. Run-time error?

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it is showing segmentation fault(core dumped) on gcc

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@ankit

here u r trying to store the value of general pointer into a constant int pointer

right?

it is trying to get some address, but getting another integer pointer value

So, will give runtime error

https://stackoverflow.com/questions/21476869/constant-pointer-vs-pointer-to-constant

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@ankit @gaurav

can u explain tis code plz

https://ideone.com/7rt9cz

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@srestha , I don't know why it is showing segmentation fault on my machine and online gdb compiller..

is it accessing memory area of any other process ?

I think , in your code , a=(int *) 10 , a= (int)10 , a=10 all are same and will give the same output..we use int* in case of pointer variable but here we r not using any pointer variable . so it will not affect anything

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* is a de-referencing operator.
*anyPtr would mean "go to the address pointed by anyPtr and then print value in it"

In your case,

 a=(int *) 10

Address 10 in memory has nothing or is in your program's bounds. So, when you are getting segfault.

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yea, rt

I think it is finding some hex value(as address are always in hex) and getting an integer value

that is why giving seg fault

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I didn't get it

@Arunav Khare .. The code srestha sent has no error. Are you getting confused between the two questions? Cause you are associating a line from her code to result of the code in the question

@srestha .. The code u sent https://ideone.com/7rt9cz is not yet clear to me.

I experimented a lot with that first line.. the code works fine even if u replace int* with float*, double* etc.. 

int a=(double*) 10; works but 

float a=(double*) 10; doesn't .. I guess it's ambiguous.

@ankitgupta.1729 in the given question p will be assigned value 10.. When *p is printed, it causes segmentation fault as it's outside address space of it

Answer 1

Refer these two link, these two posts are enough to understand about the pointers(some basic are required). Feel free to ask if you don't get something.

https://stackoverflow.com/questions/5727/what-are-the-barriers-to-understanding-pointers-and-what-can-be-done-to-overcome?rq=1

https://stackoverflow.com/questions/18481740/pointer-expressions-ptr-ptr-and-ptr (examples like you asked in your question).