RFR: JDK-8266506: [aix] Treat mapping attempt too close to BRK as a mapping error

[Thomas Stuefe]

On Tue, 4 May 2021 15:28:21 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> On AIX, in os::attempt_reserve_memory_at(), if the user specified a wish address too close to the BRK segment, we silently ignore the wish address and just map anywhere.
> 
> This is not the right behavior since the normal behavior when failing to map to a wish address is to return NULL (see JDK-8266419). Therefore we should return NULL in these cases instead.
> 
> This is a day zero bug.

Note that since we don't have that many AIX reviewers, and this only concerns AIX code, I go ahead and push. It is our port anyway, if something breaks we will have to fix it.

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PR: https://git.openjdk.java.net/jdk/pull/3859