I've been getting segfaults when running 1.14 prerelease 3 on Linux. These segfaults didn't occur on 1.14 prerelease 2. Here's a sample error:

https://pastebin.com/raw/7kZYXVSM

I checked out the error report for more details, and noticed it happens when LWJGL calls into jemalloc via JNI. The exact stack trace in LWJGL varies, but it's always the same JNI call to je_malloc. Here's a sample stack trace (with Yarn deobfuscated mappings for readability):

https://pastebin.com/raw/TJ7xzs2j

I also noticed the LWJGL version changed between Prerelease 2 and Prerelease 3. Prerelease 2 used LWJGL 3.2.1, while Prerelease 3 reverted to LWJGL 3.1.6. Suspecting this version change caused the issue, I checked out the LWJGL changelog. Sure enough, the jemalloc version was bumped to 5.2.0 from 5.1.0 in LWJGL 3.2.1, which means pre3 ships with the older jemalloc (5.1.0). To confirm this is the cause, I forced the game to run with lwjgl-jemalloc:3.2.1 and sure enough, the segfault stopped happening.

I see MC-144107 appears to have been fixed on Linux by reverting the LWJGL version, but unfortunately this is also triggering segfaults on Linux.