lldb formatters

lldb supports "summary providers" which can show a summary for non-POD data types.

Some formatters are provided in Tools/lldb/lldb_webkit.py. To have these always present when debugging in lldb, include this file in your ~/.lldbinit file:

command script import {Path to WebKit Root}/Tools/lldb/lldb_webkit.py

Writing new formatters

New formatters for common types are always welcome. They are not hard to write; see <​https://trac.webkit.org/changeset/234062> for an example of one being added.

Unit tests should be added in Tools/lldb/lldb_webkit_unittest.py (currently there are problems running these on the bots). You can run these tests manually with ./Tools/Scripts/test-webkitpy lldb_webkit_unittest

Tips and tricks for writing formatters

• Documentation is at ​https://lldb.llvm.org/varformats.html
• The lldb python bindings are documented at ​https://lldb.llvm.org/python_reference/
• Xcode caches the formatters between runs. If debugging your formatter in Xcode. you have to quit and relaunch Xcode after each change.
• You can just print from the formatter code and it will show up in Xcode's debugger output window