- 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
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.
- 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
- Create an annotated file for the detailed results. This is implied if
dir option are specified.
- Extension to use for the annotated file. Default is‘.cov`.
- 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
- 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.