Crash on launch in PruneBlockIndexCandidates #33129

1. 
   nervana21 commented at 2:09 pm on August 3, 2025: contributor

   Is there an existing issue for this?

   • I have searched the existing issues

   Current behaviour

   setBlockIndexCandidates can become empty if the chain tip is not included in the set, which violates an internal invariant and leads to a crash during FindMostWorkChain(). This issue and potential solutions were originally surfaced by ataraxia009 in #33127.

   Expected behaviour

   After pruning, the active tip must be present in the candidate set. No crash should occur in FindMostWorkChain().

   Steps to reproduce

   Mine a chain Manually remove the tip from setBlockIndexCandidates Call PruneBlockIndexCandidates() Observe that setBlockIndexCandidates no longer contains the tip -> This violates an invariant relied upon by FindMostWorkChain()

   Relevant log output

   No response

   How did you obtain Bitcoin Core

   Compiled from source

   What version of Bitcoin Core are you using?

   v29.99.0-75ed673

   Operating system and version

   Mac

   Machine specifications

   No response

2. 
   Ataraxia009 commented at 4:03 pm on August 3, 2025: none

   The issue I was addressing has nothing to do with FindMostWorkChain or a crash in it.

   The root issue that I witnessed was a crash on launch in PruneBlockIndexCandidates which is caused by the data dir reaching a bad state.

   In this state, the block validity of the block indexes in the setBlockIndexCandidates was correct, i.e.: BLOCK_VALID_TRANSACTIONS, but the block validity for the blocks that were used to to build the CoinsView and therefore the M_Chain did not have their required block validity, i.e BLOCK_VALID_SCRIPTS, the blocks with neither BLOCK_VALID_SCRIPTS nor BLOCK_VALID_TRANSACTIONS were being used as the m_chain.tip. Which should not be the case.

   This caused all the setBlockIndexCandidates to have lesser work than the m_chain.Tip. Leaving the setBlockIndexCandidates empty after the PruneBlockIndexCandidates call during launch.

   I cannot figure out how the data got to that state because it seems like this state should never happen.

3. 
   furszy commented at 4:09 pm on August 3, 2025: member

   Which version of Bitcoin-Core are you running?
4. 
   maflcko commented at 8:23 am on August 4, 2025: member

   I cannot figure out how the data got to that state because it seems like this state should never happen.

   Bitcoin Core makes heavy use of CPU, RAM and storage IO. Hardware defects might only become visible when running Bitcoin Core. You might want to check your hardware for defects.

   • Use software such as memtest86 to check your RAM.
   • Use software such as linpack, or Prime95 to check the CPU behaviour under load.
   • Use software such as smartctl, fsck, badblocks, or CrystalDiskInfo to test your storage device use.

   Source: https://bitcoin.stackexchange.com/a/12206

5. nervana21 renamed this:
   Crash when chain tip is missing from candidate set
   Crash on launch in PruneBlockIndexCandidates
   on Aug 5, 2025
6. 
   nervana21 commented at 0:40 am on August 5, 2025: contributor

   Ahh, okay, my understanding of the problem that Ataraxia009 is having is a bit better now, but I still don’t understand the problem well enough to adequately characterize it better than I’ve done in this issue. I’ve updated the title to more accurately describe what’s believed to be the source of the error
7. 
   Ataraxia009 commented at 4:43 am on August 5, 2025: none

   Which version of Bitcoin-Core are you running?

   28

8. 
   Ataraxia009 commented at 4:44 am on August 5, 2025: none

   I cannot figure out how the data got to that state because it seems like this state should never happen.

   Bitcoin Core makes heavy use of CPU, RAM and storage IO. Hardware defects might only become visible when running Bitcoin Core. You might want to check your hardware for defects.

   • Use software such as memtest86 to check your RAM.
   • Use software such as linpack, or Prime95 to check the CPU behaviour under load.
   • Use software such as smartctl, fsck, badblocks, or CrystalDiskInfo to test your storage device use.

   Source: https://bitcoin.stackexchange.com/a/12206

   Possible, but highly doubt it. Ill run some tests anyways.

   Im on a mac with CPU: Apple M2 Max

   Ill find alternatives to the above but if you have suggested ones lmk

Contributors
nervana21 Ataraxia009 furszy maflcko