Difference between identifier list and parameter list in function?

Question

For this quote:

An identifier list in a function declarator that is not part of a definition of that function shall be empty.

what is the difference between identifier list and parameter list and can someone provide an example for this quote.

It would be useful to specify which section of which document you are using, when you give standard quotes. — M.M, Feb 21 '17 at 12:51
i think you can find your answer here... http://stackoverflow.com/questions/18820751/identifier-list-vs-parameter-type-list-in-c — Isha Goyal, Feb 21 '17 at 12:53
@Sabrina there is no 6.7.5.3 in the current standard. Which is why I suggested specifying which document you are reading. You must have some old standard. — M.M, Feb 21 '17 at 12:59

score 7 · Accepted Answer · edited May 23 '17 at 12:00

7

The "identifier list" is only used in obsolete "K&R style" functions. New code written today would never use it. You can see more details here: https://stackoverflow.com/a/3092074/4323

It's something like this:

void func(identifier-list)
declaration-list
{
    body
}

When they say it shall be empty, they mean that even admitting the possibility of ancient code, you are not allowed to have this in a declaration which does not define a function. So for example this is not allowed:

void func(x) int x;

edited May 23 '17 at 12:00

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answered Feb 21 '17 at 12:52

John Zwinck

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What about `shall be empty` ? – Sabrina Feb 21 '17 at 12:52
It is the opposite switch them . – Sabrina Feb 21 '17 at 12:53
@Sabrina that's pretty clear isn't it? "shall be empty" means there cannot be anything in between the parentheses, for a declaration that is not a definition. So you cannot write `void func(x);` – M.M Feb 21 '17 at 12:54
@M.M so the quote is only restricted to old style.( K&R ) – Sabrina Feb 21 '17 at 12:58
The standard is written this way because the grammar rules for function declarations treat `func()` as having an empty identifier-list between the parentheses. So identifier-lists have to be allowed in function declarations ... but only if they are empty. – zwol Feb 23 '17 at 18:58

Vlad from Moscow · Answer 2 · 2017-02-21T13:17:33.283

Identifier list without identifiers' definitions says nothing about the types of function parameters. So it does not make sense to specify an identifier list for a function declaration when it is not at the same time a function definition.

So this restriction of the cited quote is used.

Here is an example

#include <stdio.h>

void f();

int main(void) 
{
    int x = 10;
    f( x );

    return 0;
}

void f( x ) 
int x;
{
    printf( "x = %d\n", x );
}

When a parameter list is used the compiler can check a call of a function that valid arguments are passed to the function. So it is better always to use parameter list instead of identifier list.

Difference between identifier list and parameter list in function?

2 Answers2