4.2.3 Using the debugger when tracing

:break

Trace keyword

:break form

If form evaluates to non- nil , the debugger is entered directly from trace . If it returns nil , tracing continues as normal. This option lets you force entry to the debugger by supplying a form as simple as t .

Upon entry to the traced function, the standard trace information is printed, any supplied :before forms are executed, and then form is evaluated.

:break-on-exit

Trace keyword

Like :break , this option allows you to enter the debugger from trace . It differs in that the debugger is entered after the function call is complete.

Upon exit from the traced function, the standard trace information is printed, and then form is evaluated. Finally, any supplied :after forms are executed.

:backtrace

Trace keyword

Generates a backtrace on each call to the traced function. backtrace can be any of the following values:

:quick

Like the :bq debugger command.

t

Like the :b debugger command.

:verbose

Like the :b :verbose debugger command.

:bug-form

Like the :bug-form debugger command.