C++ Passing an array of struct as function argument

Question

C++: What's the difference between the code as shown below AND simultaneously omitting the keyword struct in the functional declaration and definition -- code seems to work the same both ways ?

#include <iostream>
#include <string>

struct student{
            int age;
            int number;
        };

void printme( struct student m[]);    // if 'struct' is omitted the code works as fine

int main()
{        
    student s[3];
    s[0].age = 10;
    s[0].number = 333;

    printme(s);

    return 0;
}

void printme( struct student m[]){
        printf("George age and number: %d, %d \n", m[0].age, m[0].number);
    }

It's mostly backward compatibility with c - both options are the same. — Daniel, Jun 12 '16 at 19:42
Doesn' [this work fine](http://coliru.stacked-crooked.com/a/ce2d2f77caad639d) actually? I don't get your quesiton. — πάντα ῥεῖ, Jun 12 '16 at 19:44
Change the keyword `struct` to `class` and you'll see why it works. [C++ Does Not Have Structs](http://stackoverflow.com/questions/32719880/why-theres-not-stdis-struct-type-trait/34108140#34108140) — Carey Gregory, Jun 12 '16 at 19:52
@πάνταῥεῖ OP is asking why it works _without_ the `struct` keyword in the function declaration. — Carey Gregory, Jun 12 '16 at 19:55
@πάνταῥεῖ I don't think it's a dup. Very close, but not quite. — Carey Gregory, Jun 12 '16 at 19:57
If you make a typo (e.g. `struct studten m[]`) then you get an error message in a different place , or even silent undefined behaviour, depending whether or not you included `struct` — M.M, Jun 12 '16 at 21:52

score 0 · Answer 1 · edited May 23 '17 at 12:24

0

Notice that you are using c++ and not c, so here there is no difference, you can use both of these options.

Check this: Passing structs to functions for more.

edited May 23 '17 at 12:24

Community

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1

answered Jun 12 '16 at 19:43

gsamaras

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I assume that in C you HAVE TO use the 'struct', while in CPP it's optional ? Probably for code compatibility ? Thanx – Ivo Peev Jun 12 '16 at 19:45
Yes @IvoPeev. In [tag:C], unless you had some `typedef` you would receive a compiler error! – gsamaras Jun 12 '16 at 19:46
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Why `class` instead of `struct` if both are the same thing? – juanchopanza Jun 12 '16 at 19:55
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_"I would encourage you to use a class instead of a struct"_ Why's that? The keyword `class` and the keyword `struct` both introduce classes. – Lightness Races in Orbit Jun 12 '16 at 20:00
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@IvoPeev By the way, the language is called C++ (and cpp is the C preprocessor). – melpomene Jun 12 '16 at 20:00
Oh OK @LightnessRacesinOrbit and juanchopanza, edited. :) – gsamaras Jun 12 '16 at 20:02

score 0 · Answer 2 · answered Jun 12 '16 at 19:46

This comes from C, where you had to specify struct (or use typedef). In C++, there's no difference as long as you don't use the same id for both a struct and an object. Please, don't do it, but if your really want to, then you'll need to write e.g. struct student for the type and student for the object (which is not necessarily of type student, if you really want to confuse everyone). Basically, C+ coding standards tend to recommend skipping struct and never having the same id for struct and object.

C++ Passing an array of struct as function argument

2 Answers2