RFR: 7903586: Revisit jextract constant classes

[Jorn Vernee]

On Wed, 29 Nov 2023 10:58:56 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This PR removes the use of jextract constant classes, and falls back to a simpler code generation strategies which move the various constants closer to where they belong:
> 
> * for structs and callbacks, the constants are added to the class/interface being generated;
> * for the header class, we use a local holder class per function to hold the method handle and function descriptor constants.
> 
> This scheme results in much less generated code (as no constant class is emitted), but with the same performance and laziness as the old scheme.
> 
> When working with the code, I've decided to simplify the handling of constant generation, in the spirit of what was recently done with the introduction of string templates. That is, instead of using a magic `Constant` class, which has methods to generate getters/setters for a given constant, I converted much of the code into "static" string templates, so that it's easier to see which code gets generated when staring at the jextract code. As a result, the `Constant` class has been removed.

src/main/java/org/openjdk/jextract/impl/FunctionalInterfaceBuilder.java line 40:

> 38: final class FunctionalInterfaceBuilder extends ClassSourceBuilder {
> 39: 
> 40:     private static final String MEMBER_MODS = "static";

Seems unused? (I think I prefer just 'inlining' the mods in the string template if they don't change, as you've done)

-------------

PR Review Comment: https://git.openjdk.org/jextract/pull/145#discussion_r1409134312