RFR: 8329086: Clean up java.desktop native compilation

[Magnus Ihse Bursie]

On Tue, 26 Mar 2024 19:46:00 GMT, Phil Race <prr at openjdk.org> wrote:

>> This is a follow-up on [JDK-8328680](https://bugs.openjdk.org/browse/JDK-8328680), making the same kind of cleanup to java.desktop. Some code needed more special treatment here, so there is some additional effects outside of the modules/java.desktop directory. The code was also in worse shape than other modules, so some additional changes to the build logic where needed.
>
> make/modules/java.desktop/lib/Awt2dLibraries.gmk line 569:
> 
>> 567: LIBJAWT_EXTRA_HEADER_DIRS := \
>> 568:     include \
>> 569:     #
> 
> A syntax question - what does the trailing # do / mean here ?
> Superficially I'd expect this to expand to "include #"
> which means there'd be a # embedded when you append the other folders below ..

`#` is the line comment marker in makefiles.

What you see here is a common pattern in our makefiles, typically used in multi-line lists. The trailing # is a trick to avoid having a special treatment on the last line (without a ``), which is all too easy to forget, and very hard to debug.

This particular list is very short, so `LIBJAWT_EXTRA_HEADER_DIRS := include` would have yielded the same result, and I would normally have chosen that syntax, but in this case the list will be conditionally appended to just below, so in a conceptual sense the list is much longer, but the limited syntax in makefiles does not allow for us to express this in a better way.

> make/modules/java.desktop/lib/Awt2dLibraries.gmk line 848:
> 
>> 846:           -framework Metal \
>> 847:           -framework OpenGL \
>> 848:           -framework QuartzCore \
> 
> The re-ordering here happens to be small, and it looks like some one already might have been doing somethings lexically, but this again points to the need for running tests as well as building.

Here, as in many places, there have been attempts at keeping the lists sorted, but unfortunately this has not been kept 100%. :-(

The extraction of -ljava is essential for the upcoming JDK_LIB rewrite.

Once again, if you have any suggestions to what tests you think I should run, let me know!

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PR Review Comment: https://git.openjdk.org/jdk/pull/18486#discussion_r1540223963
PR Review Comment: https://git.openjdk.org/jdk/pull/18486#discussion_r1540225111