The purpose of this module is to find which part of the program has been
used by a certain goal. Usage is defined in terms of clauses for which
the head unification succeeded. For each clause we count how often it
succeeded and how often it failed. In addition we track all call
sites, creating goal-by-goal annotated clauses.
This module relies on the SWI-Prolog tracer hooks. It modifies these
hooks and collects the results, after which it restores the debugging
environment. This has some limitations:
- The performance degrades significantly (about 10 times)
- It is not possible to use the debugger during coverage analysis
- The cover analysis tool is currently not thread-safe.
The result is represented as a list of clause-references. As the
references to clauses of dynamic predicates cannot be guaranteed, these
are omitted from the result.
- - Relies heavily on SWI-Prolog internals. We have considered using
a meta-interpreter for this purpose, but it is nearly impossible
to do 100% complete meta-interpretation of Prolog. Example
problem areas include handling cuts in control-structures
and calls from non-interpreted meta-predicates.
- show_coverage(:Goal) is semidet
- show_coverage(:Goal, +Options) is semidet
- show_coverage(:Goal, +Modules:list(atom)) is semidet
- Report on coverage by Goal. Goal is executed as in once/1. Options
- Provide a detailed report on Modules. For backwards
compatibility this is the same as providing a list of
modules in the second argument.
- Create an annotated file for the detailed results.
This is implied if the
dir option are
- Extension to use for the annotated file. Default is
- Dump the annotations in the given directory. If not
given, the annotated files are created in the same
directory as the source file. Each clause that is
related to a physical line in the file is annotated
with one of:
|###||Clause was never executed.|
|++N||Clause was entered N times and always succeeded|
|--N||Clause was entered N times and never succeeded|
|+N-M||Clause has succeeded N times and failed M times|
|+N*M||Clause was entered N times and succeeded M times|
All call sites are annotated using the same conventions,
--- is used to annotate subgoals that were
true (default), add line numbers to the annotated file.
- Controls using ANSI escape sequences to color the output
in the annotated source. Default is
- report_hook(+Succeeded, +Failed) is semidet[multifile]
- This hook is called after the data collection. It is passed a list
of objects that have succeeded as well as a list of objects that
have failed. The objects are one of
- The specified clause
- call_site(ClauseRef, PC, PI)
- A call was make in ClauseRef at the given program counter to
the predicate indicated by PI.