TACL Reference Manual

UTILS:TACL Commands and Functions
HP NonStop TACL Reference Manual—429513-018
8-51
DEBUGGER Function
DEBUGGER Function
If tracing is enabled (see #TRACE Built-In Variable on page 9-408), the TACL trace
facility displays the next line to be executed, then immediately invokes the
_DEBUGGER function before executing that code. You can set breakpoints, modify
variables, and invoke TACL commands while debugging.
For an example of _DEBUGGER function use, see the TACL Programming Guide.
current-trace-value
is the value of #TRACE, which always equals -1 (true) when invoked by TACL.
reason-for-entry
is TRACE or BREAK.
Considerations
•
When #TRACE is not zero, TACL calls _DEBUGGER immediately after displaying
the code that is next to be invoked. In this case, current-trace-value is always -1
and reason-for-entry is always TRACE.
•
It is possible to replace _DEBUGGER with a debugging function of your own
devising.
•
If TACL is about to invoke a variable on which you have set a breakpoint, TACL
invokes _DEBUGGER. _DEBUGGER prompts with - num- (the current history
number). At this point you can enter a command. If it is a TACL command, it is
passed on to TACL for execution. If it is a _DEBUGGER command, _DEBUGGER
executes it. The _DEBUGGER commands are:
B[REAK] [ variable-level ]
sets an invocation breakpoint on a variable level. If you omit variable-
level, the command displays all breakpoints currently set.
C[LEAR] { variable-level | * }
clears the invocation breakpoint for the specified variable-level. If you use
the asterisk (*), the command clears all breakpoints.
D[ISPLAY] variable-level
displays the contents of the specified variable level.
M[ODIFY] variable-level
allows you to modify the contents of the specified variable level.
_DEBUGGER current-trace-value reason-for-entry