debug_messages
By default, debug and debug(Group) messages are only printed
when the debug flag is turned on. These messages are also suppressed
when compiling code with the optimize flag turned on. This tool
supports selective enabling of debug and debug(Group) messages
in normal and debug modes.
API documentation
This tool API documentation is available at:
../../docs/library_index.html#debug-messages
For general information on debugging, open in a web browser the following link and consult the debugging section of the User Manual:
Loading
This tool can be loaded using the query:
| ?- logtalk_load(debug_messages(loader)).
Testing
To test this tool, load the tester.lgt file:
| ?- logtalk_load(debug_messages(tester)).
Usage
The tool provides two sets of predicates. The first set allows enabling
and disabling of all debug and debug(Group) messages for a given
component. The second set allows enabling and disabling of
debug(Group) messages for a given group and component for
fine-grained control.
Upon loading the tool, all debug messages are skipped. The user is then
expected to use the tool API to selectively enable the messages that
will be printed. As an example, consider the following object, part of a
xyz component:
:- object(foo).
:- public([bar/0, baz/0]).
:- uses(logtalk, [print_message/3]).
bar :-
print_message(debug(bar), xyz, @'bar/0 called').
baz :-
print_message(debug(baz), xyz, @'baz/0 called').
:- end_object.
Assuming the object foo is compiled and loaded in normal or debug
mode, after also loading this tool, bar/0 and baz/0 messages
will not print any debug messages:
| ?- {debug_messages(loader), foo}.
...
yes
| ?- foo::(bar, baz).
yes
We can then enable all debug messages for the xyz component:
| ?- debug_messages::enable(xyx).
yes
| ?- foo::(bar, baz).
bar/0 called
baz/0 called
yes
Or we can selectively enable only debug messages for a specific group:
| ?- debug_messages::disable(xyx).
yes
| ?- debug_messages::enable(xyx, bar).
yes
| ?- foo::(bar, baz).
bar/0 called
yes