46 lines
1.9 KiB
Markdown
46 lines
1.9 KiB
Markdown
---
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title: "Obscure Qt: GDB pretty printers"
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date: 2023-05-02
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draft: false
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tags:
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- Qt
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series:
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- Obscure Qt
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---
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**Edit:** This was written before my projects were switched to Qt6, and I'm not aware of a Qt6 pretty printer solution (if you do, let me know in a comment below.) If you're using CLion, check out the [Qt6 pretty printer plugin](https://github.com/winseros/Qt6Renderer).
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Outside of Qt Creator, GDB has a hard time understanding Qt times and you'll regularly get garbage or unusable debugging output.
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Luckily, [GDB has a system where you can use Python scripts](https://github.com/ruediger/Boost-Pretty-Printer/blob/master/HACKING.org) to print information from custom types[^1]. The printers we're using is [Ezike Ebuka's GDB_Printers](https://invent.kde.org/ebuka/gdb_printers). First clone the repository, and extract it somewhere where you won't accidentally delete it. Here I copy it into my Development folder:
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```bash
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$ cd ~/Development
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$ git clone git@invent.kde.org:ebuka/gdb_printers.git
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```
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Then edit your `~/.gdbinit` file and add this to it (or create it if you haven't already):
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```python
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python
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import sys
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# change the path below to the correct path
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sys.path.append('/home/josh/Development/gdb_printers')
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from printers import register_qt_printers
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register_qt_printers(None)
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end
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set print pretty on
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```
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Now if you run GDB again, you'll get pretty prints for a lot of Qt types! This includes QString, QVector, and of course QList:
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If you want a full list of supported types, take a look in [qtprinters.py](https://invent.kde.org/ebuka/gdb_printers/-/blob/master/printers/qtprinters.py).
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[^1]: Just make sure your GDB has been compiled with Python support, or else this won't work.
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