Byron Marohn

Would it be possible to add another variant to /forceload that has this synchronous behavior? As mentioned, a lot of mechanisms rely on this for correctness, even if it causes lag.

We did this ourselves in 1.16 on a Bukkit/Paper server -

/forceload add x1 z1 x2 z2

• loads synchronously (vanilla behavior in 1.16), allowing subsequent commands to access everything in that chunk the same tick

/forceload addlazy x1 z1 x2 z2 [namespace:myfunction]

• loads chunks asynchronously (sounds like the new behavior in 1.17, possibly taking several ticks) and optionally runs a function when those chunks have all finished loading

I have this same problem using the Linux/other .jar launcher.

Same two errors. Removing the -XX:+CMSIncrementalMode java argument removes the incremental CMS warning. That done, still getting:
Error: Could not find or load main class net.minecraft.client.main.Main

Tested with latest jar-based launcher version available on the Minecraft.net website (1.6.82-j)

Tested on two different Windows 10 systems with up-to-date Java version 1.8.0_151 from Oracle.

I also tried deleting the .minecraft folder and the launcher jar and starting from a clean re-download of the jar - same deal.

This worked yesterday (10/24/2017 midnight PST) but no longer worked this morning (10/25/2017 noon PST)

Additionally, it seems to be independent of what minecraft version you select or is even installed in a directory the launcher knows about. I have several old copies with independent minecraft versions each in different %APPDATA%/.minecraft directories (via changing that environment variable) and at least 1.10.2, 1.12.1, and 1.12.2 are affected, which leads me to believe it is strictly a launcher bug.

Also, launching a version of Minecraft Forge has exactly the same problem as launching the Vanilla minecraft version.