K&R-style variadic functions

[Jacob Carlborg]

On 2012-07-17 17:11, Regan Heath wrote:

> Ahh, I've been looking at the ANSI C spec and assuming that is what
> you're basing things off, K&R C was pre-ANSI C and may have different
> rules.  I think you should probably aim to be ANSI C compliant and
> above, and ignore K&R.

This page says otherwise:

http://en.wikipedia.org/wiki/ANSI_C#Compliance_detectability

"...while an obsolescent non-prototype declaration is used otherwise. 
Those are still ANSI-compliant as of C99 and C90, but their use is 
discouraged".

> Looking at the ANSI C spec again, section 6.7.5.3, item 10 says:
>
> "The special case of an unnamed parameter of type void as the only item
> in the list specifies that the function has no parameters."
>
> So, "void" indicates no parameters..
>
> Item 14 is also applicable and says:
>
> "An identifier list declares only the identifiers of the parameters of
> the function. An empty list in a function declarator that is part of a
> definition of that function specifies that the function has no
> parameters. The empty list in a function declarator that is not part of
> a definition of that function specifies that no information about the
> number or types of the parameters is supplied." 124)
>
> The latter part of that is applicable to declarations in header files
> (the former is for definitions in c files);  "The empty list in a
> function declarator that is /not part of a definition of that function/
> specifies that /no information about the number or types of the
> parameters is supplied/."
>
> So, a function like:
>      int foo();
>
> in a header "specifies that no information about the number or types of
> the parameters is supplied".
>
> However footnote 124) says see 6.1.6, and 6.1.6 says:
>
> 6.11.6 Function declarators
> The use of function declarators with empty parentheses (not
> prototype-format parameter type declarators) is an obsolescent feature.
>
> So, coming full circle, it seems like I'm right after all .. I think.
> "void" is required to indicate no parameters and () is obsolete in ANSI C.

It's still in the standard.

-- 
/Jacob Carlborg