What is the significance of asterisks postfixing a variable type in a method header?

Question

I have been trying to learn C as a programming language, and have been trying to solve sample problems on site like LeetCode in C programs. When I was reading over some of the skeleton code that was provided as a function header for a problem on LeetCode that I want to solve in C, the function header had asterisks post fixing some of the types, specifically like this:

int* twoSum(int* nums, int numSize, int target, int* returnSize) {
   /* Code goes here */
}

After doing a fair bit of reading, I learned that prefixing a variable with an asterisk when declaring a variable reserves the variable as a pointer, but I have not been able to find anything about what it means when the type specifier itself is post fixed with an asterisk.

A more interesting function declaration can look like for example void f( size_t, size_t, int [][*] ); where the asterisk is between square braces.:) — Vlad from Moscow, Jul 11 '19 at 17:24
Please get yourself a [proper **C book**](https://stackoverflow.com/q/562303/918959). If there is any language that should not be self-taught from random websites it would be C. — Antti Haapala -- Слава Україні, Jul 12 '19 at 07:43

score 3 · Accepted Answer · answered Jul 11 '19 at 17:09

3

The spaces there don't matter.

int* nums is identical to int *nums. So are int * nums and int*nums.

All four of these declare nums as pointer to int.

It's a matter of style preference (though I wouldn't use that last one), with no effect on the generated code.

answered Jul 11 '19 at 17:09

Thomas Jager

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A site that is sometimes useful when trying to parse C declarations is [cdecl](https://cdecl.org/). – Thomas Jager Jul 11 '19 at 17:14
So to clarify, the header means that in the method header, I was passed two integer pointers, two actual integer variables, and I am expected to return a pointer to an array of integers? – Fuse Jul 11 '19 at 17:17
You return a pointer to `int`. Whether that is to be treated as an array is for the context. – Weather Vane Jul 11 '19 at 17:19
Thank you very much. This was very helpful. – Fuse Jul 11 '19 at 17:21
Quite often, it is the same as the destination pointer that was passed, and returning `NULL` is used to indicate failure - cf `fgets()`. – Weather Vane Jul 11 '19 at 17:23
The last one is horrible. I'd never use it. – S.S. Anne Jul 11 '19 at 17:58
But beware in declarations: `int* a, b;` makes `a` a pointer to int, but `b` jjust an int. – FredK Jul 11 '19 at 18:55

What is the significance of asterisks postfixing a variable type in a method header?

1 Answers1