User`s guide

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Appendix A: dbx Commands
when [expression|variable] in procedure {command-list}
Inspects the value at every source line within a given
procedure. If it has changed, executes the command list.
If the expression is of type pointer, look at the data pointed
to and watch until it changes. If the expression is not of type
pointer, look at the 32 bits at that address (assume the
expression evaluates to an address).
when if expression {command-list}
Evaluates the expression before executing each source line.
If it is true, executes the command list.
when at line if expression {command-list}
Evaluates the expression at the given source line. If it is true,
executes the command list.
when in procedure if expression {command-list}
Evaluates the expression at every source line within a given
procedure. If it is true, executes the command list.
when [expression1|variable] if expression2 {command-list}
Checks if the value of the variable has changed. If it has
changed and the expression is true, executes the command
list.
If expression1 is of type pointer, look at the data pointed to
and watch until it changes. If expression1 is not of type
pointer, look at the 32 bits at that address (assume the
expression evaluates to an address).
when [expression1|variable] at line if expression2 {command-list}
Checks if the value of the variable has changed each time
the line is executed. If the value has changed and the
expression is true, executes the command list.
If expression1 is of type pointer, look at the data pointed to
and watch until it changes. If expression1 is not of type
pointer, look at the 32 bits at that address (assume the
expression evaluates to an address).
when [expression1|variable] in procedure if expression2 {command-
list}
Checks if the value of variable has changed at each source