IDE Window: Breakpoints

From Free Pascal wiki

Deutsch (de) English (en) русский (ru)


Main Menu > View > Debug Windows > BreakPoints


You must setup the debugger and start the project to debug it. Only then will this window be useful.


Note: About Watchpoints:

When setting the watchpoint the variable - which should be watched - must be in scope. (That is the program must be running and stopped at a breakpoint where the variable can be seen).
For that reason watchpoints are only valid until the app exits and then will be disabled. On the next debug they must be enabled again while stopped at a location where it is in scope.

Breakpoint list

Breakpoint list.png

There are 3 kind of breakpoints:

Source Breakpoint
Specified by Unit-name and Line-number. The execution will be interrupted before the pascal statement on the specified line is executed. Can be set by clicking the gutter in the source-editor.
Address Breakpoint
Specified by an address. The execution will be interrupted before the assembler statement at the address is executed. Can be set by clicking the gutter in disassembler window.
Data/Watch Breakpoint
Specified by the name of a variable. The execution will be interrupted when the variable is changed. It can also detect read access. Support for this depends on the platform used.

Data displayed

Line/Length: Depending on the type of the breakpoint the following is displayed:
  • Source Breakpoint:
    Filename/Address: The name of the file where the breakpoint is set.
    Line/Length: The line-number where the breakpoint is set.
  • Address Breakpoint:
    Filename/Address The address of the breakpoint. This type of breakpoint is useful if there is no source available.
    Line/Length: This is empty
  • Data Breakpoint:
    Filename/Address: The name of the variable.
    Line/Length: Will show the scope ("Global" / "Declaration") and the mode ("Read" / "Write" / "Read/Write")
Pass Count
How many times the enabled breakpoint has been reached. If a "Hitcount" is defined for this breakpoint, the debugger will perform the break action(s) when the hitcount is reached.



debugger enable.png Enable/debugger disable.png Disable
Enables/Disables individual breakpoint(s).
laz delete.png Remove
Deletes the selected Breakpoint(s)
debugger enable all.png Enable all/debugger disable all.png Disable all
Enables/Disables all breakpoints.
menu clean.png Delete all
Deletes all Breakpoints
menu environment options.png Properties
Change the properties of the current/selected breakpoint.

Context menu

Breakpoint list popmenu.png
View Source
Jump to the source. (Only Source-Breakpoints)
Opens a property dialog for the requested type of breakpoint. The location/address/variable can be set in the property dialog.
Toggle the enabled state for individual breakpoint(s)
Deletes the selected Breakpoint(s)
Clears or sets the group for the breakpoint. A list of existing groups will be in the menu. With "Set new group" a new group can be created.
Enable all/Disable all
Enables/Disables all breakpoints.
Delete all
Deletes all Breakpoints
Disable all in same source/Enable all in same source
Enables/Disables all breakpoints in the same unit as the current selected breakpoint. (Only Source-Breakpoints)
Delete all in same source
Deletes all Breakpoints in the same unit as the current selected breakpoint. (Only Source-Breakpoints)

Breakpoint properties

BreakPoint Properties.png

Location of the breakpoint
The breakpoint will only be triggered and perform the specified actions, if the condition evaluates to true. This can for example be used to test if a variable has reached a critical value.
Currently only very basic expressions are allowed. (GDB must be able to understand the expression)
NOTE #1: The IDE does only apply a very limited pascal syntax fixing to the condition (#48 is escaped as char with ord val 48), so it needs to be C-like, so GDB understands the expression. eg: "i=2" or somechar='a'. Remember that the string (or rather char) value must be wrapper in single quotes, not double quotes.
NOTE #2: Strings can not be compared. They are seen as pchar, so they can only be compared to an address: "str=0x5a0b40". Chars in a string can be compared (index is zero based/pchar) "(s[0]='a')and(s[1]='b')". And strings can be compared as PChar (zero terminated): $_streq(^char(MyString), "ValueToCompare") (with double quotes) See:
The breakpoint will be ignored until it has been hit the specified amount of times. One scenario where this is useful, if an event is triggered by the focus change (between IDE and debugged app) when the app is paused/resumed. The ignored passes of the breakpoint to not alter the focus.
NOTE: #1 The hitcount starts at 0. So if you want to break on the 10th iteration, set the HitCount to 9.
NOTE: #2 The hit count doesn't reset until you stop/start the debugging or actually delete the breakpoint and set it again (without the need to stop/start the debug session).
Auto continue after
This also avoids the focus change between IDE and app. It however indicates the execution line in the source editor, which leads to a visible indication. If the time is long enough watches might be evaluated.
A breakpoint can be is one group (one only). Groups can be used with the Enable/Disable group feature.
  • Break: Pause the application. The application can be continued with the Run command or any of the stepping commands
  • Enable/Disable Group: Enable or Disable all breakpoints in the given group(s). Usually 2 breakpoints would be set, one to enable, the other to disable. The breakpoints in the specified groups could then be enabled (or disabled) only, if they occur between the 2 points. The breakpoints that are changed could be in subroutines, that are called sometimes between the 2 points, but also from other locations.
  • Eval Expression: Evaluates the expression and writes the value to the debug event log
  • Log Message: Writes the message to the debug event log
  • Log Callstack: Writes the callstack to the debug event log
  • Take a snapshot: Evaluates all Watches, Locals, Callstack, Threads, and adds it to the snapshots in the History dialog.