Stand on a partial block, like cake, slab, or chest. Run the command "/setblock ~ ~ ~ stone" The block above the one you are standing on will be set to stone. This only occurs if the block is thick enough, if run on a carpet for example, it will work correctly. Interestingly, if run on a 4-layer thick snow cover, it will work correctly, even though that is the same height as cake, which doesn't work correctly. This is because the player sinks 2 pixels into snow.
This bug only occurs when the command is directly run by the player, if you instead run "/execute @p ~ ~ ~ setblock ~ ~ ~ stone", it will work correctly.
Linked issues
Comments
Sonicwave
Sonicwave
Coordinates in commands run by players
Nvm, it seems that I've misread the title. On second thought this seems different than MC-67515, since that issue doesn't involve partial blocks at all; rather it seems that entities are being summoned from the center of the command block (as opposed to the bottom, as with players). Using either
"/summon Creeper ~ ~2 ~ {NoAI:1}"or an execute with it summons a NoAI Creeper exactly 2 blocks above the player's feet, so /summon seems to work differently.
Basically this is the opposite of MC-56253 (execute places the block 1 block higher than just using /setblock).
If it is setblock, I think that the Y coordinates will round up instead of down. If for example, if the block you are standing on is 0.850 blocks high, the setblock will round up.
Actually this is a dupe of MC-67515 (which based on this report seems to affect all relative coordinates, not just with /summon).While 56253 has command blocks in the background, it talks about /execute from the player, not a command block (notice the command in the chat in the 1st screenshot).