RFR: 8308031: Linkers should reject unpromoted variadic parameters [v2]

[Jorn Vernee]

On Wed, 31 May 2023 23:36:33 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/foreign/Linker.java line 368:
>> 
>>> 366:  * <h3 id="variadic-funcs">Variadic functions</h3>
>>> 367:  *
>>> 368:  * Variadic functions (e.g. a C function declared with a trailing ellipses {@code ...} at the end of the formal parameter
>> 
>> Optional suggestion for improvement (maybe now, or maybe later). When reading this great para, I understand that there are two things that fall under the "variadic function" umbrella. Some are declared with `...` and some with `()`. This is a very good definition and I wonder if we should expand a bit more on it - e.g. in a way, we never explain what a variadic function is - we merely define it by saying how it is declared in C. I wonder if we might very very briefly explain that in C, some functions (variadic functions) can take a variable number of parameters. Then we go on to say that these functions can be declared in two ways (e.g. ellipsis and prototype-less). Perhaps if we used a bullet-list to define the two ways in which variadic function can be declared, the definition could stand out even more?
>
> Also, should we say somewhere that, for prototype-less functions, `firstVariadicArg` should always have an index of 0 (e.g. any other value is illegal, trivially). It's not super important, just one of those little things that can reinforce understanding.

> Perhaps if we used a bullet-list to define the two ways in which variadic function can be declared, the definition could stand out even more?

Yes, I think this is a good idea. I'll do another pass.

> Also, should we say somewhere that, for prototype-less functions, firstVariadicArg should always have an index of 0

I think this is also a good idea. It help hammer the point home.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14225#discussion_r1212426680