C Programming

Question

Can someone explain the output of the following program? Need the logic behind the Output.

The Output is:

4
8
1
1
4
8
8
(nil)
0x1
4

Comments

Please type the code instead of the snapshot. It would be easier to evaluate then.

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Can you tell me why do the following code sniplets result in different output?

 

printf("%d", sizeof(NULL));
printf("%d", sizeof *(NULL));

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For 

printf("%d", sizeof(NULL));

See this:

https://stackoverflow.com/questions/4141666/why-sizeof-is-equivalent-to-1-and-sizeofnull-is-equivalent-to-4-in-c-langu

For 

printf("%d", sizeof *(NULL));

I think it gives 1 because we are asking about the size of value stored at NULL, and its size is 1.

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Thanks.
Can you please explain what is happening over here:
 

printf("%d", sizeof*(1?NULL:(int*)1));

How exactly is it evaluted.

 

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1?NULL:(int*)1

I could be wrong, but this is what I think happened here. This ternary operator evaluates to NULL, which is typecasted to integer because we used "1" in the expression and thus size of integer pointer, which is same as integer, is returned.

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For

printf("%d", sizeof *(NULL));

I think it gives 1 because we are asking about the size of value stored at NULL, and its size is 1.

 
Whose size is 1? The size of value stored at NULL is 1? How can anything be stored at NULL.
From what I understood, sizeOf(NULL), its returning 4, since its returning size of Pointer pointing to NULL.

But what is *(NULL) returning? Its de-referrencing a void pointer basically, right? is it a char? Will sizeof *(NULL) always return 1?

Also, for the next question:

1?NULL:(int*)1

I could be wrong, but this is what I think happened here. This ternary operator evaluates to NULL, which is typecasted to integer because we used "1" in the expression and thus size of integer pointer, which is same as integer, is returned.

But that's not the case here. I tried executing it on a compiler where Pointer, and Integer have different size and Even when the size of Integer Pointer, is not same as Size of Integer, its still returning size of Integer.
Have a look: https://ideone.com/YjM1Pj

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Hmm, then my thinking was wrong. Maybe it is compiler dependent. I can't really say for sure. I'm clueless like you now.