Attached screenshot and minimal world repro. If you stand at the location indicated in the screenshot and save/reload the world, you will hit the bug.
Root cause has been narrowed down to:
Item frame with some contained item at X=0 / Z=0 in chunk
Mounted on block in adjacent chunk
Behind that block, a comparator is sensing the item frame
Stand in a chunk adjacent to the chunk containing the item frame, save and load the world, and all❓ entities in the chunk with the item frame will be duplicated a huge number of times.
From MC-56077:
This is an item duplication glitch that involves the new comparator measuring item frame feature in snapshot 14w18.
How to Replicate This Bug:
1.) Find the east/west edge of a chunk. (Preferably using F3)
2.) Place any redstone current-carrying block on the west side of the chunk edge.
3.) Place an item frame on the block, facing east.
4.) Place a comparator next the block, pointing the opposite direction that the item frame is facing, so that the comparator is in a different chunk than the item frame.
5.) Put any block you want to duplicate into the item frame.
6.) Quit and re-join the world. You will now have a stack of item frames and the item you put in the frame.
Related issues
is duplicated by
MC-53219
Item frames and comparators, multiplies entities
MC-55073
Entity Duplication Glitch
MC-56077
Item Duplication Glitch Using Item Frames, Comparators [14w18-14w21]
MC-56233
dupe glitch
MC-56582
Duplication glitch
MC-56844
Dupelication Glitch (Chunk Glitch)
MC-56908
Contents of Chests spilled in front of them (whilst also being in the chests)+ 100s of item frames on the ground
MC-56940
Item frames spawning loads of what was inside them and the item frame itself
MC-58954
Duplication glitch in chunk
MC-59257
item / entity duplication glitch
MC-59717
Item frame facing east + Comparator out the back = duplication bug
MC-61299
Important Entities Multiplication
MC-62398
Minecraft dupe crashes online multipler servers CAUSES CRASH ON SMP
MC-62745
Item Duplication Glitch using Comparators - Dupe 1 block to 8 stacks
MC-62945
Extreme entity duplication using Item Frames
MC-64373
Duplication glitch using item frames
MC-64904
Bug of Item Frame and Redstone.
MC-66196
Dupe glitch with Item frames & comparators
MC-67789
Long-standing duplication bug.
MC-68286
duplication glitch in survival with the new item frames putting out a redstone signal
MC-68704
Duilpiction bug
relates to
Attachments
Comments
migrated
kumasasa
Confirmed.
migrated
Also attaching log file, which has some nice long stack overflow exceptions that were ignored when loading. Last level load in the log is related to the screenshot.
kumasasa
Duplication causes exception (or exception causes duplication):
[07:21:34 INFO]: Client> [07:21:30] [Server thread/ERROR]: Couldn't load chunk
[07:21:34 INFO]: Client> s: Exception getting block type in world
[07:21:34 INFO]: Client> at tj.f(SourceFile:1168) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at tp.a(SourceFile:158) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at ave.a(SourceFile:291) ~[14w11b.jar:?]
...
[07:21:34 INFO]: Client> at ny.d(SourceFile:117) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at akh.b(SourceFile:287) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at akh.f(SourceFile:282) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at akh.c(SourceFile:218) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at akh.a(SourceFile:2360) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> Caused by: java.lang.StackOverflowError
[07:21:34 INFO]: Client> at java.lang.Package.<init>(Unknown Source) ~[?:1.7.0_51]
[07:21:34 INFO]: Client> at java.lang.Package.<init>(Unknown Source) ~[?:1.7.0_51]
[07:21:34 INFO]: Client> at java.lang.Package$1.run(Unknown Source) ~[?:1.7.0_51]
[07:21:34 INFO]: Client> at java.lang.Package$1.run(Unknown Source) ~[?:1.7.0_51]
[07:21:34 INFO]: Client> at java.security.AccessController.doPrivileged(Native Method) ~[?:1.7.0_51]
[07:21:34 INFO]: Client> at java.lang.Package.defineSystemPackage(Unknown Source) ~[?:1.7.0_51]
[07:21:34 INFO]: Client> at java.lang.Package.getSystemPackage(Unknown Source) ~[?:1.7.0_51]
[07:21:34 INFO]: Client> at java.lang.Package.getPackage(Unknown Source) ~[?:1.7.0_51]
[07:21:34 INFO]: Client> at java.lang.Class.getPackage(Unknown Source) ~[?:1.7.0_51]
[07:21:34 INFO]: Client> at org.apache.logging.log4j.core.impl.ThrowableProxy.resolvePackageElement(ThrowableProxy.java:437) ~[log4j-core-2.0-beta9.jar:2.0-beta9]
[07:21:34 INFO]: Client> at org.apache.logging.log4j.core.impl.ThrowableProxy.resolvePackageData(ThrowableProxy.java:395) ~[log4j-core-2.0-beta9.jar:2.0-beta9]
[07:21:34 INFO]: Client> at org.apache.logging.log4j.core.impl.ThrowableProxy.<init>(ThrowableProxy.java:115) ~[log4j-core-2.0-beta9.jar:2.0-beta9]
[07:21:34 INFO]: Client> at org.apache.logging.log4j.core.impl.ThrowableProxy.<init>(ThrowableProxy.java:98) ~[log4j-core-2.0-beta9.jar:2.0-beta9]
[07:21:34 INFO]: Client> at org.apache.logging.log4j.core.impl.Log4jLogEvent.<init>(Log4jLogEvent.java:114) ~[log4j-core-2.0-beta9.jar:2.0-beta9]
[07:21:34 INFO]: Client> at org.apache.logging.log4j.core.impl.Log4jLogEvent.<init>(Log4jLogEvent.java:90) ~[log4j-core-2.0-beta9.jar:2.0-beta9]
[07:21:34 INFO]: Client> at org.apache.logging.log4j.core.impl.DefaultLogEventFactory.createEvent(DefaultLogEventFactory.java:49) ~[log4j-core-2.0-beta9.jar:2.0-beta9]
[07:21:34 INFO]: Client> at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:365) ~[log4j-core-2.0-beta9.jar:2.0-beta9]
[07:21:34 INFO]: Client> at org.apache.logging.log4j.core.Logger.log(Logger.java:110) ~[log4j-core-2.0-beta9.jar:2.0-beta9]
[07:21:34 INFO]: Client> at org.apache.logging.log4j.spi.AbstractLogger.error(AbstractLogger.java:609) ~[log4j-api-2.0-beta9.jar:2.0-beta9]
[07:21:34 INFO]: Client> at ny.f(SourceFile:139) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at ny.c(SourceFile:81) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at ny.d(SourceFile:117) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at akh.b(SourceFile:287) ~[14w11b.jar:?]
...
[07:21:34 INFO]: Client> at akh.x(SourceFile:2377) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at akh.c(SourceFile:2398) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at anw.g(SourceFile:168) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at ann.g(SourceFile:131) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at ann.i(SourceFile:101) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at ann.b(SourceFile:197) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at anw.a(SourceFile:133) ~[14w11b.jar:?]
[07:21:34 INFO]: Client> at akh.f(SourceFile:2821) ~[14w11b.jar:?]Duplication does not occur if comparator gets removed.
migrated
Still exists in latest snapshot. I noticed the duplication also occurs if you stand in the same chunk in the repro world; there may be some conditions to it as I didn't observe this in a previous repro environment.
migrated
I testet it and it still works in 14w20b.
The item frame has to be in a different chunk than the block it's hanging on in positive X or Z direction
Not only the item frame and its content get duplicated but also every other entity in the chunk the item frame is in.
migrated
Confirmed for 14w21a/b.
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If you execute this bug with a villager you will get duplicates of the villager - the only way this seems to happen in the game.
migrated
Confirmed for 14w26a
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confirmed for 14w26c
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Confirmed for 14w27b
migrated
I should mention also that we originally discovered this issue accidentally in a multiplayer world: Besides the minimal repro, if you nether-portal in to an adjacent chunk in an area away from spawn (rather than just loading a single player world standing in an adjacent chunk) it also triggers the bug (and may crash the server, I think depending on the number of entities it results in)
migrated
Confirmed for 14w28a
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Confirmed for 14w28b.
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Confirmed for 14w29b.
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Confirmed for 14w30a
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Confirmed in 14w30b.
migrated
I cant run my snapshot server because of this and will not be able to update to 1.8 as this bug crashes online servers
migrated
Confirmed for 14w31a
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Confirmed for 14w32a
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I can also confirm for 14w32a. Screenshot attached.
migrated
Confirmed for 14w32c
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Confirmed for 14w32d
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Confirmed for 14w33a
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Confirmed for 14w33b
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Confirmed for 14w33c
michael