Copying output from console causes large mem usage/OOM #887

1. 
   fanquake commented at 2:23 pm on September 4, 2025: member

   Moved from https://github.com/bitcoin/bitcoin/issues/33285.

   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. 
   hebasto commented at 2:23 pm on September 6, 2025: member

   I can confirm this issue on Ubuntu 24.04 with the system’s Qt 6.4.2.

   However, a static build using Qt 6.7.3 from depends works perfectly. Perhaps this Qt issue was resolved upstream at some point?

3. 
   davidgumberg commented at 6:38 pm on September 9, 2025: contributor

   However, a static build using Qt 6.7.3 from depends works perfectly. Perhaps this Qt issue was resolved upstream at some point?

   I experience this issue linking against system Qt 6.9.1, so I do not think this has been fixed upstream.

   But in our depends build we set -no-feature-textmarkdownwriter:

   https://github.com/bitcoin-core/gui/blob/689a32197638e92995dd8eb071425715f5fdc3a4/depends/packages/qt.mk#L103

   and when that feature is disabled, QTextEditMimeData won’t try to convert the selection to markdown, avoiding the problematic function:

   0void QTextEditMimeData::setup() const
   1{
   2    // [ Populate other mime data formats... ]
   3#if QT_CONFIG(textmarkdownwriter)
   4    that->setData("text/markdown"_L1, fragment.toMarkdown().toUtf8());
   5#endif
   6    that->setText(fragment.toPlainText());
   7}
   

   https://github.com/qt/qtbase/blob/b617d1176593963a2a9ed21dd5d9a63e84a09400/src/widgets/widgets/qwidgettextcontrol.cpp#L3538-L3540

4. hebasto renamed this:
   GUI (?): Copying output from console causes large mem usage/OOM
   Copying output from console causes large mem usage/OOM
   on Sep 10, 2025
5. hebasto referenced this in commit ee42d59d4d on Sep 10, 2025
6. hebasto closed this on Sep 10, 2025

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Contributors
fanquake hebasto davidgumberg