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GNU Emacs Lisp Reference Manual

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18.2.15 Instrumenting Macro Calls

When Edebug instruments an expression that calls a Lisp macro, it needs additional information about the macro to do the job properly. This is because there is no a-priori way to tell which subexpressions of the macro call are forms to be evaluated. (Evaluation may occur explicitly in the macro body, or when the resulting expansion is evaluated, or any time later.)

Therefore, you must define an Edebug specification for each macro that Edebug will encounter, to explain the format of calls to that macro. To do this, use def-edebug-spec.

Macro: def-edebug-spec macro specification
Specify which expressions of a call to macro macro are forms to be evaluated. For simple macros, the specification often looks very similar to the formal argument list of the macro definition, but specifications are much more general than macro arguments.

The macro argument can actually be any symbol, not just a macro name.

Here is a simple example that defines the specification for the for example macro (see section 13.6.2 Evaluating Macro Arguments Repeatedly), followed by an alternative, equivalent specification.

 
(def-edebug-spec for
  (symbolp "from" form "to" form "do" &rest form))

(def-edebug-spec for
  (symbolp ['from form] ['to form] ['do body]))

Here is a table of the possibilities for specification and how each directs processing of arguments.

t
All arguments are instrumented for evaluation.

0
None of the arguments is instrumented.

a symbol
The symbol must have an Edebug specification which is used instead. This indirection is repeated until another kind of specification is found. This allows you to inherit the specification from another macro.

a list
The elements of the list describe the types of the arguments of a calling form. The possible elements of a specification list are described in the following sections.

18.2.15.1 Specification List  How to specify complex patterns of evaluation.
18.2.15.2 Backtracking in Specifications  What Edebug does when matching fails.
18.2.15.3 Specification Examples  To help understand specifications.


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