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 that have
fired, separated in clauses that succeeded at least once and clauses
that failed on each occasion.
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.
- To be done
- - Provide detailed information organised by predicate. Possibly
annotate the source with coverage information.
- 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 executed N times and always succeeded|
|--N||Clause was executed N times and never succeeded|
|+N-M||Clause was succeeded N times and failed M times|
- assert_cover(+Port, +Frame) is det
- Assert coverage of the current clause. We monitor two ports: the
unify port to see which clauses we entered, and the exit
port to see which completed successfully.