Writing void fun(int *tab); and void fun(int tab[]) is the same?

Question

As in topics title. When I write: void fun(int *tab){} is it the same as writing void fun(int tab[]){} ?

For readability if a function is expecting base address of an array, you can write the later one. If its just a pointer, you can write former one. — Sam, Nov 02 '13 at 17:09

score 3 · Accepted Answer · answered Nov 02 '13 at 16:53

3

Yes.

void fun(int *tab){}
void fun(int tab[]){}
void fun(int tab[10]){}  //whatever the size is

are all the same to the compiler. The array, with the size or not, decays to a pointer when passed as a function argument.

In practice, avoid using the last one, as it may give the implication that the size is known to the function, while actually it's not.

answered Nov 02 '13 at 16:53

Yu Hao

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which makes it some of the most misleading syntactic sugar to a novice programmer... – StoryTeller - Unslander Monica Nov 02 '13 at 16:54
@YuHao: just one more question before I accept your answer ;) Why would I ever write the last one, I mean: `void fun(int tab[10]){}` - whats the point of doing this? What exactly does it mean? – nullpointer Nov 02 '13 at 17:08
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@nullpointer Arrays have a size, like `int arr[10];`, just when an array is passed as function argument, it's converted to a pointer to the first element, so the size is ignored. – Yu Hao Nov 02 '13 at 17:10

score 2 · Answer 2 · answered Nov 02 '13 at 16:49

2

Yes it is, and no, the second version won't let you figure out the size of the array inside the function. It still decays to a pointer. :)

answered Nov 02 '13 at 16:49

Luchian Grigore

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How could I figure out the size of the array with the first version? – nullpointer Nov 02 '13 at 16:51
@nullpointer, You can't. Use `std::array` or `std::vector` or something. – chris Nov 02 '13 at 16:51
@nullpointer directly you can't. Use a `std::vector`, pass the size as a parameter, or mark the last element with a special value. – Luchian Grigore Nov 02 '13 at 16:52
@nullpointer, you can't do that in the first version either. But some use the second in a misguided attempt to do so. – StoryTeller - Unslander Monica Nov 02 '13 at 16:52
@jrok: I always do that. But it was interesting what Luchian Grigore wrote, I thought that there is another 'magic' way of doing this ;) – nullpointer Nov 02 '13 at 16:53
@nullpointer also read http://stackoverflow.com/questions/7966964/what-does-this-c-code-mean – Luchian Grigore Nov 02 '13 at 16:54

score 1 · Answer 3 · answered Nov 02 '13 at 17:16

Yes it is same..Whenever you declare an array say int tab[] in your program.. and if you want to pass that array to some other function then you actually pass the base address location of that array i.e. &tab[0], which is pointed by pointer that you use as argument in function, int *tab... This actually is call by reference..

Writing void fun(int *tab); and void fun(int tab[]) is the same?

3 Answers3