There was a remark from Thomas Stuefe https://github.com/openjdk/jdk24u/pull/175

Hmm, okay.

That means that when we build on an older machine, and Linux kernels change the constant in newer kernel releases, we may use the wrong number.

What I would do is this:

#define SEGV_BNDERR_value 3
#if defined(SEGV_BNDERR)
STATIC_ASSERT(SEGV_BNDERR == SEGV_BNDERR_value);
#else
#define SEGV_BNDERR SEGV_BNDERR_value
#endif
The static assert will alert us if we build on a newer Linux version and turns out we were wrong with our assumed number.