OpenJDK 11.0.27 on macOS 15: expression is not an integral constant expression

[Dave Allured - NOAA Affiliate]

On Sun, Apr 20, 2025 at 11:29 AM Joshua Root <jmr at macports.org> wrote:

> On 21/4/2025 01:27, Nils Breunese wrote:
> > I created a draft pull request to bump the openjdk11 port to version
> 11.0.27 (https://github.com/macports/macports-ports/pull/28212), but it
> looks like this line:
> >
> >       AO_UNUSED_MBZ = (-1)<<13, // options bits reserved for future use.
> >
> > in src/jdk.pack/share/native/common-unpack/constants.h results in this
> error on macOS 15:
> >
> >       expression is not an integral constant expression
> >
> > On macOS 13 and 14 the build succeeds without this error.
> >
> > I am not too familiar with C++, but does this seem related to a change
> in macOS 15? Any idea what should be done to fix the build on macOS 15?
>
> It would be a compiler change rather than a change in the OS. I believe
> using bitwise shift operators on a negative value has undefined
> behaviour. The fix would be to express the constant in a well-defined
> way, for example directly as a hex value, or by shifting a positive
> value and then negating afterwards. I don't know how this constant is
> used, so I can't say what would be most appropriate.


cppreference.com says that is undefined behavior.  That constant is defined
as an enum, which I think means only that it needs to be a correctly
defined integer.  Try something like this:

     AO_UNUSED_MBZ = (~((1<<13) - 1))
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