gdb-natvis

This implements Natvis based pretty printing in GDB. GDB exposes a python API for writing pretty printers of certain types which is used by this project.

This project will allow creating custom pretty printers for GDB without having to write and deploy python code for every type. It will also allow using the existing visualizers written for Visual Studio without changes.

Dependencies

• GDB built with Python 3.6
• libclang (tested with version 5.0) with Python bindings

Installation

Clone this repository somewhere and add the following to your .gdbinit:

python
sys.path.insert(0, "/path/to/gdb-natvis/src")
try:
    import printer
except ImportError:
    printer = None
    import traceback
    traceback.print_exc()
else:
    printer.add_natvis_printers()
end

This will automatically try to load natvis files if GDB tries to pretty-print a type. The auto-discovery of natvis files works by determining the file of the type being printed and then examining every parent directory for .natvis files. This will obviously not work in all cases so this also adds a add-nativs command to GDB.

This command can be called with the path to one or more .natvis files which will then be loaded and used by subsequent pretty printing operations.

Supported Features

This already supports a wide array of features available in the Natvis system:

• Type name matching with template parameters (including wildcards)
• DisplayString with embedded expressions. Format specifiers are parsed but not used at the moment
• Condition for most XML elements
• Most Expand items are supported
  • Item is fully supported
  • ArrayItems is supported for the simple case (Size and ValuePointer)
  • IndexListItems including $i parameters
  • ExpandedItem
  • Limited support for Synthetic. Only the display string part is supported since synthetic items are not possible with the current GDB API

Known issues

• The expression parser does not support all syntax elements yet
• Global variables are not resolved
• GDB issue: MI clients (such as CDT or CLion) do not receive the to_string value of a python pretty printer. This hides the DisplayString value since that uses to_string. As a workaround, the display string is added as a child instead. There is a GDB patch that fixes this issue: https://sourceware.org/bugzilla/show_bug.cgi?id=11335