What use is void?

[Kevin Bracey]

In message <[email protected]>

Or not even fall through -- you can insert a blank

return;

in the function for the same effect (immediate return to caller,
undefined return value).

Not as of C99. Both of your examples are illegal in C99.

In such cases, the Prime Directive of Misplaced Efficiency Tuning
dictates that we use 'return;' in place of 'return 0;', to save
the single "load" instruction.

Indeed. I don't think there was a Misplaced Efficiency Tuning representative
on the C99 committee, alas.

 

[Arthur J. O'Dwyer]

Not as of C99. Both of your examples are illegal in C99.

Hmm... N869 says you're right.

6.8.6.4 The return statement

Constraints

[#1] A return statement with an expression shall not appear
in a function whose return type is void. A return statement
without an expression shall only appear in a function whose
return type is void.


I wonder where I became so sure of what I posted earlier... I
distinctly remember seeing the opinion I posted, somewhere else
recently. I thought it was somewhere in N869, but apparently
not.

Thanks for the correction.

-Arthur

 

[Kevin Bracey]

In message <[email protected]>

I wonder where I became so sure of what I posted earlier... I
distinctly remember seeing the opinion I posted, somewhere else
recently. I thought it was somewhere in N869, but apparently
not.

Well, it was perfectly legal to "return;" in a non-void function before C99;
maybe you saw it in a C90 context.

 

[Darrell Grainger]

Hello, I was wondering, does it make any difference if you write

void foo(int x)
{
/* insert code here */
}

or

foo(int x)
{
/* insert code here */
}

What is the difference?? Both ways the function wont return anything,
right? What is the point in writing void? Is it merely a cosmetic feature?

Incorrect. The second version will return an int. All too often new
programmers assume that having no return value indicates no return value
is necessary. The truth is that the second version returns an int. These
are the same:

int foo(int x)
{
/* insert code here */
/* make sure you return an int */
}

foo(int x)
{
/* insert code here */
/* make sure you return an int */
}

The purpose of void is to tell the compiler the function does not default
to returning an int.

--
Ian Tuomi
Jyväskylä, Finland

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--
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