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/* Part of SWI-Prolog
Author: Jan Wielemaker and Anjo Anjewierden
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org/
Copyright (c) 2011-2022, University of Amsterdam
VU University Amsterdam
CWI, Amsterdam
SWI-Prolog Solutions b.v.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
:- module(prolog_breakpoints,
[ set_breakpoint/4, % +File, +Line, +CharPos, -Id
set_breakpoint/5, % +Owner, +File, +Line, +CharPos, -Id
set_breakpoint_condition/2, % +Id, +Cond
delete_breakpoint/1, % +Id
breakpoint_property/2 % ?Id, ?Property
]).
:- autoload(library(debug), [debug/3]).
:- autoload(library(error), [existence_error/2]).
:- autoload(library(lists), [nth1/3, member/2]).
:- autoload(library(prolog_clause), [clause_info/4, clause_name/2]).
/** <module> Manage Prolog break-points
This module provides an interface for development tools to set and
delete break-points, giving a location in the source. Development tools
that want to track changes to breakpoints must use user:message_hook/3
to intercept these message terms:
* breakpoint(set, Id)
* breakpoint(delete, Id)
Note that the hook must fail after creating its side-effects to give
other hooks the opportunity to react.
*/
%! set_breakpoint(+File, +Line, +Char, -Id) is det.
%! set_breakpoint(+Owner, +File, +Line, +Char, -Id) is det.
%
% Put a breakpoint at the indicated source-location. File is a current
% sourcefile (as reported by source_file/1). Line is the 1-based line
% in which Char is. Char is the position of the break.
%
% First, '$clause_from_source'/4 uses the SWI-Prolog clause-source
% information to find the last clause starting before Line.
% '$break_pc' generates (on backtracking), a list of possible
% breakpoints.
%
% Note that in addition to setting the breakpoint, the system must be
% in debug mode for the breakpoint to take effect. With threading
% enabled, there are various different ways this may be done. See
% debug/0, tdebug/0 and tdebug/1. Therefore, this predicate does *not*
% enable debug mode.
%
% @arg Owner denotes the file that _owns_ the clause. set_breakpoint/5
% is used to set breakpoints in an included file in the context of the
% Owner main file. See source_file_property/2.
set_breakpoint(File, Line, Char, Id) :-
set_breakpoint(File, File, Line, Char, Id).
set_breakpoint(Owner, File, Line, Char, Id) :-
debug(break, 'break_at(~q, ~d, ~d).', [File, Line, Char]),
'$clause_from_source'(Owner, File, Line, ClauseRefs),
member(ClauseRef, ClauseRefs),
clause_info(ClauseRef, InfoFile, TermPos, _NameOffset),
( InfoFile == File
-> '$break_pc'(ClauseRef, PC, NextPC),
debug(break, 'Clause ~p, PC=~p NextPC=~p', [ClauseRef, PC, NextPC]),
'$clause_term_position'(ClauseRef, NextPC, List),
debug(break, 'Location = ~w', [List]),
range(List, TermPos, SubPos),
arg(1, SubPos, A),
arg(2, SubPos, Z),
debug(break, 'Term from ~w-~w', [A, Z]),
Z >= Char, !,
Len is Z - A,
b_setval('$breakpoint', file_location(File, Line, A, Len))
; print_message(warning, breakpoint(no_source(ClauseRef, File, Line))),
'$break_pc'(ClauseRef, PC, _), !,
nb_delete('$breakpoint')
),
debug(break, 'Break at clause ~w, PC=~w', [ClauseRef, PC]),
'$break_at'(ClauseRef, PC, true),
nb_delete('$breakpoint'),
known_breakpoint(ClauseRef, PC, _Location, Id).
range(_, Pos, _), var(Pos) =>
fail.
range(List, parentheses_term_position(_,_,Pos), SubPos) =>
range(List, Pos, SubPos).
range([], Pos, SubPos) =>
SubPos = Pos.
range([H|T], term_position(_, _, _, _, PosL), SubPos) =>
nth1(H, PosL, Pos),
range(T, Pos, SubPos).
range(exit, Pos, SubPos) =>
arg(2, Pos, End),
Dot is End,
EndDot is Dot+1,
SubPos = Dot-EndDot.
:- dynamic
known_breakpoint/4, % ClauseRef, PC, Location, Id
breakpoint_condition/4, % Id, CondString, CondTerm, VarOffsets
break_id/1.
next_break_id(Id) :-
retract(break_id(Id0)),
!,
Id is Id0+1,
asserta(break_id(Id)).
next_break_id(1) :-
asserta(break_id(1)).
%! delete_breakpoint(+Id) is det.
%
% Delete breakpoint with given Id. If successful,
% print_message(breakpoint(delete, Id)) is called. Message hooks
% working on this message may still call breakpoint_property/2.
%
% @error existence_error(breakpoint, Id).
delete_breakpoint(Id) :-
integer(Id),
known_breakpoint(ClauseRef, PC, _Location, Id),
!,
'$break_at'(ClauseRef, PC, false).
delete_breakpoint(Id) :-
existence_error(breakpoint, Id).
%! breakpoint_property(?Id, ?Property) is nondet.
%
% True when Property is a property of the breakpoint Id. Defined
% properties are:
%
% * file(File)
% Provided if the breakpoint is in a clause associated to a
% file. May not be known.
% * line_count(Line)
% Line of the breakpoint. May not be known.
% * character_range(Start, Len)
% One-based character offset of the break-point. May not be
% known.
% * clause(Reference)
% Reference of the clause in which the breakpoint resides.
breakpoint_property(Id, file(File)) :-
known_breakpoint(ClauseRef,_,_,Id),
clause_property(ClauseRef, file(File)).
breakpoint_property(Id, line_count(Line)) :-
known_breakpoint(_,_,Location,Id),
location_line(Location, Line).
breakpoint_property(Id, character_range(Start, Len)) :-
known_breakpoint(ClauseRef,PC,Location,Id),
( Location = file_location(_File, _Line, Start, Len)
-> true
; break_location(ClauseRef, PC, _File, SubPos),
compound(SubPos),
arg(1, SubPos, Start),
arg(2, Start, End),
nonvar(Start), nonvar(End),
Len is End+1-Start
).
breakpoint_property(Id, clause(Reference)) :-
known_breakpoint(Reference,_,_,Id).
breakpoint_property(Id, condition(Cond)) :-
known_breakpoint(_,_,_,Id),
breakpoint_condition(Id, Cond, _CondTerm, _VarOffsets).
location_line(file_location(_File, Line, _Start, _Len), Line).
location_line(file_character_range(File, Start, _Len), Line) :-
file_line(File, Start, Line).
location_line(file_line(_File, Line), Line).
%! file_line(+File, +StartIndex, -Line) is det.
%
% True when Line is the 1-based line offset in which we find
% character StartIndex.
file_line(File, Start, Line) :-
setup_call_cleanup(
prolog_clause:try_open_source(File, In),
stream_line(In, Start, 1, Line),
close(In)).
stream_line(In, _, Line0, Line) :-
at_end_of_stream(In),
!,
Line = Line0.
stream_line(In, Index, Line0, Line) :-
skip(In, 0'\n),
character_count(In, At),
( At > Index
-> Line = Line0
; Line1 is Line0+1,
stream_line(In, Index, Line1, Line)
).
/*******************************
* FEEDBACK *
*******************************/
:- initialization
prolog_unlisten(break, onbreak),
prolog_listen(break, onbreak).
onbreak(exist, ClauseRef, PC) :-
known_breakpoint(ClauseRef, PC, _Location, Id),
!,
break_message(breakpoint(exist, Id)).
onbreak(true, ClauseRef, PC) :-
!,
debug(break, 'Trap in Clause ~p, PC ~d', [ClauseRef, PC]),
with_mutex('$break', next_break_id(Id)),
( nb_current('$breakpoint', Location)
-> true
; break_location(ClauseRef, PC, File, A-Z)
-> Len is Z+1-A,
Location = file_character_range(File, A, Len)
; clause_property(ClauseRef, file(File)),
clause_property(ClauseRef, line_count(Line))
-> Location = file_line(File, Line)
; Location = unknown
),
asserta(known_breakpoint(ClauseRef, PC, Location, Id)),
break_message(breakpoint(set, Id)).
onbreak(false, ClauseRef, PC) :-
debug(break, 'Remove breakpoint from ~p, PC ~d', [ClauseRef, PC]),
delete_breakpoint(ClauseRef, PC).
onbreak(retract, ClauseRef, PC) :-
debug(break, 'Remove breakpoint from ~p, PC ~d (due to retract)',
[ClauseRef, PC]),
delete_breakpoint(ClauseRef, PC).
delete_breakpoint(ClauseRef, PC) :-
clause(known_breakpoint(ClauseRef, PC, _Location, Id), true, Ref),
retractall(breakpoint_condition(Id, _, _, _)),
call_cleanup(break_message(breakpoint(delete, Id)), erase(Ref)).
break_message(Message) :-
print_message(informational, Message).
%! break_location(+ClauseRef, +PC, -File, -Pos) is det.
%
% True when File and Pos represent the file and subterm position term
% for the goal called at PC in ClauseRef.
%
% @arg Pos is a subterm position term (see `subterm_positions` option
% of read_term/3, where positions are character positions in File. The
% first two argument always hold the start and end of the term.
break_location(ClauseRef, PC, File, SubPos) :-
clause_info(ClauseRef, File, TermPos, _NameOffset),
'$fetch_vm'(ClauseRef, PC, NPC, _VMI),
'$clause_term_position'(ClauseRef, NPC, List),
debug(break, 'ClausePos = ~w', [List]),
range(List, TermPos, SubPos),
debug(break, 'Subgoal at: ~p', [SubPos]).
/*******************************
* MESSAGES *
*******************************/
:- multifile
prolog:message/3.
prolog:message(breakpoint(no_source(ClauseRef, _File, Line))) -->
[ 'Failed to find line ~d in body of clause ~p. Breaking at start of body.'-
[Line, ClauseRef]
].
prolog:message(breakpoint_condition_error(Id, Error)) -->
[ 'Exception while evaluating breakpoint ~p condition:'-[Id], nl,
prolog:translate_message(Error)
].
prolog:message(breakpoint(SetClear, Id)) -->
setclear(SetClear),
breakpoint(Id).
setclear(set) -->
['Breakpoint '].
setclear(exist) -->
['Existing breakpoint '].
setclear(delete) -->
['Deleted breakpoint '].
breakpoint(Id) -->
breakpoint_name(Id),
( { breakpoint_property(Id, file(File)),
breakpoint_property(Id, line_count(Line))
}
-> [ ' at ', url(File:Line) ]
; []
).
breakpoint_name(Id) -->
{ breakpoint_property(Id, clause(ClauseRef)) },
( { clause_property(ClauseRef, erased) }
-> ['~w'-[Id]]
; { clause_name(ClauseRef, Name) },
['~w in ~w'-[Id, Name]]
).
/*******************************
* CONDITIONAL BREAKPOINTS *
*******************************/
%! set_breakpoint_condition(+Id, +Cond) is det.
%
% Set a condition for of the breakpoint with given Id. The condition
% Cond is a string that represents a Prolog goal to be invoked
% whenever the breakpoint is reached, if goal fails the breakpoint is
% skipped and execution commences normally.
%
% Variables in Cond that match by name to variables in the source
% definition of the clause in which the breakpoint is located are
% unified with the corresponding runtime value of the clause variables
% in the current execution frame, before evaluating the condition
% goal.
%
% @error existence_error(breakpoint, Id).
set_breakpoint_condition(Id, Cond) :-
known_breakpoint(ClauseRef, _PC, _Location, Id),
!,
term_string(CondGoal, Cond, [variable_names(Bindings)]),
clause_info(ClauseRef, _InfoFile, _TermPos, NameOffset),
clause_property(ClauseRef, module(Module)),
names_offsets(Bindings, NameOffset, FrameOffsetsCondVars),
retractall(breakpoint_condition(Id, _, _, _)),
asserta(breakpoint_condition(Id, Cond, Module:CondGoal, FrameOffsetsCondVars)).
set_breakpoint_condition(Id, _Cond) :-
existence_error(breakpoint, Id).
:- multifile prolog:break_hook/7.
prolog:break_hook(Clause, PC, Frame, _Choice, _Goal, true, Action) :-
known_breakpoint(Clause, PC, _, Id),
( breakpoint_condition(Id, _CondString, CondGoal, FrameOffsetsCondVars)
-> check_breakpoint_condition(Id, Frame, CondGoal,
FrameOffsetsCondVars, Action)
; Action = trace
).
check_breakpoint_condition(Id, Frame, CondGoal, FrameOffsetsCondVars, Action) :-
maplist(unify_with_frame_variable(Frame), FrameOffsetsCondVars),
( catch(CondGoal,
Error,
print_message(warning,
breakpoint_condition_error(Id, Error)))
-> Action = trace
; Action = continue
).
unify_with_frame_variable(Frame, Offset-Var) :-
prolog_frame_attribute(Frame, argument(Offset), Var).
names_offsets([Name=Var|T], NameOffset, OffsetsVars) :-
( arg(Offset, NameOffset, Name)
-> OffsetsVars = [Offset-Var|R],
names_offsets(T, NameOffset, R)
; names_offsets(T, NameOffset, OffsetsVars)
).
names_offsets([], _, []).
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