GUI (?): Copying output from console causes large mem usage/OOM #33285

1. 
   instagibbs commented at 6:25 pm on September 2, 2025: member

   Is there an existing issue for this?

   • I have searched the existing issues

   Current behaviour

   Running the GUI on mainnet, I open the console, run:

   getblocktemplate '{"rules": ["segwit"]}'

   everything acts normally until then. If I then try to copy the test, memory usage blows out:

   on release build, jumps from <2GB to >7GB memory

   on debug build, it jumps to dozens of GB, often causing OOM and kills the process.

   Expected behaviour

   I expect the memory usage to not blow up on basic operations.

   Steps to reproduce

   Already detailed.

   Relevant log output

   No logs after the block generated is tested for validity.

   How did you obtain Bitcoin Core

   Compiled from source

   What version of Bitcoin Core are you using?

   master@7e58c94112d0

   Operating system and version

   Ubuntu 24.04.2 LTS

   Machine specifications

   64GB of memory

2. fanquake added the label GUI on Sep 3, 2025
3. 
   fanquake commented at 10:54 am on September 3, 2025: member

   cc @hebasto
4. 
   maflcko commented at 10:59 am on September 3, 2025: member

   I have the impression that this was already reported years ago, but I couldn’t find a reference either.
5. 
   fanquake commented at 11:53 am on September 3, 2025: member

   I guess if it’s known and has just never been fixed, maybe we should add a warning that copying from the console (too much?) might crash your node.
6. 
   w0xlt commented at 5:36 pm on September 3, 2025: contributor

   On debug build, it seems to use all available memory. Is it something related to Qt?
7. 
   davidgumberg commented at 11:30 pm on September 3, 2025: contributor

   I have opened a fix here: https://github.com/bitcoin-core/gui/pull/886.
8. 
   fanquake commented at 2:23 pm on September 4, 2025: member

   Moved to https://github.com/bitcoin-core/gui/issues/887.
9. fanquake closed this on Sep 4, 2025

   ---

Contributors
instagibbs fanquake maflcko w0xlt davidgumberg

Labels
GUI