DWARF

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About

DWARF (Debugging With Attributed Record Formats) is a debugging data format. Dwarf is needed when debugging with FpDebug.

Debugging information is generated by the compiler together with the machine code. Debugging information is read by the debugger. Debugging information is a representation of the relationship between the executable program and the original source code. This information is encoded into a pre-defined format and stored alongside the machine code.

The FPC provides the following DWARF-compatible debugging information with command line parameters:

  • -gw Generate DWARFv2 debug information (same as -gw2)
  • -gw2 Generate DWARFv2 debug information
  • -gw2 -godwarfsets Generate DWARFv2 debug information, but include DWARFv3 description for sets ("set of SomeEnum").
  • -gw3 Generate DWARFv3 debug information
  • -gw4 Generate DWARFv4 debug information

Missing dwarf-style debugging-data-format will result in a message:

Enable Dwarf 2 prompt.png

Choosing a DWARF version for Debugging

The Debugger Status page has as overview which versions are supported and recommended: Debugger_Status#Debug_Info_Support

If a project switches between several Debugger Backends, settings should either be adapted or the lowest recommended version should be used.

Differences between versions

Fpc encodes some data types differently depending on the version of DWARF used. This comprises: - dynamic arrays - short and long strings - TObjects - variants

Especially the info for Long/ShortString may affect how different debugger backends display those types. Long/ShortString do not have their own encoding, they are described as either record, array of char or pchar.

DWARFv2 (with/without sets)

For GDB "DWARFv2 with sets" is the best option. Testing shows that, if using other (v3 and up) DWARF (as generated by FPC) then GDB is more likely to crash.

DWARFv3

DWARFv3 and up, encodes identifiers keeping their case. Instead of "TMYFOOCLASS" the debugger can display "TMyFooClass".