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Light bulb  Note: For more information about the Free Pascal debugger see


Tip: LazDebuggerFp works best with DWARF 3

  • LazDebuggerFp is a debugger integrated into the IDE based on FpDebug.
  • It many cases it is simply referred to as FpDebug (making that term ambiguous)...
  • LazDebuggerFp requires DWARF debug info to be enabled in the project options.

Using LazDebuggerFp in the IDE

The package is installed in the IDE by default.

The debugger can be selected in Tools > Options > Debugger > Debugger Backend

Related topics

Debugger specific options

Tools | Options | Debugger | Debugger Backend | FpDebug integrated Dwarf-debugger
(Linux only) Redirect StdOut to an existing tty
(Windows only) If the IDE has a console, debugging an app that also has a console will normally share the existing console. Setting this to "True" will open a new console for the debugged app.
See FpDebug-Watches-Intrinsic-Functions#Settings
By default "Step out" will return to the caller, and pause execution in the middle of the line from which the call originally came. This allows to "Step in" again, if several calls are made on that line.
For example; Foo(Func1(), Func2()); contains 3 calls, each of the 3 can be stepped in (if they have debug info)
If the debugger should stop at hardcoded "int3" breakpoints.
Limits the amount of Memory the debugger will use for a single read. This can prevent errors if incorrect size information proclaims a structure is tens of Gigabyte big.
This may also protect from dummy declarations like "type TMaxArray = array [0..$7FFFFFFF] of byte; PMaxArray = ^TMaxArray". Such types are never fully allocated. They only act as accessor.
The limit applies to the structure as a whole. Individual fields/elements can be read if they are smaller than the limit.
Length in chars to cut off strings. Protects against corrupted data.
Length in elements to cut off array. Protects against corrupted data.
PChar (and strings in dwarf2) have no length info (or not determinable to the debugger). The debugger must read memory until it finds a #0. If no #0 is found the debugger will stop searching at this length.
MaxStackStringLen, MaxStackArrayLen, MaxStackNullStringSearchLen
Same as above, but applied when evaluating stack-frames (content for the Stack window). Due to the limited space in the stack window, one might choose lower limits.
If configured, the debugger can run converters (See here) on data (Currently only passing variant to SysVarToLStr). In arrays and structures each entry/field will be converted if it is a variant. This limits the amount of entries in an array that will be converted.
If an array contains structures with several variant fields, then each field is counted as conversion.
If the debug inspector fetches an array, then this limit does not apply to the array as a whole. It will rather apply to each entry within the array (should those entries be themself arrays). This is so, that the limit applies to each row displayed by the Inspector.
Similar to MaxArrayConversionCnt, but applies to all conversions. I.e., also outside of arrays, like fields of a class.
This limit also applies to the whole of an inspected value in the inspector.
Unlike what happens in the inspector, in the watches window an expanded watch (sub-watches) does not count as a whole. Each sub-watch counts individually.

The debugger currently does not give an indication if a value was cut off. This will be implemented in future.