dbg_ieval.erl

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%% ``The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved via the world wide web at http://www.erlang.org/.
%% 
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%% 
%% The Initial Developer of the Original Code is Ericsson Utvecklings AB.
%% Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings
%% AB. All Rights Reserved.''
%% 
%%     $Id$
%%
-module(dbg_ieval).

-export([eval/3,exit_info/5]).
-export([eval_expr/3]).
-export([check_exit_msg/3,exception/4,in_use_p/2]).
-export([stack_level/0, bindings/1, stack_frame/2, backtrace/1]).

-include("dbg_ieval.hrl").

%%====================================================================
%% External exports
%%====================================================================

%%--------------------------------------------------------------------
%% eval(Mod, Func, Args) -> Meta
%%   Mod = Func = atom()
%%   Args = [term()]
%%   MFA = {Mod,Func,Args} | {Mod,Func,Arity} | {Fun,Args}
%%   Arity = integer()
%%   Meta = pid()
%% Entry point from debugged process (dbg_debugged).
%% Immediately returns the pid for the meta process.
%% The evaluated value will later be sent as a message to
%% the calling process.
%%--------------------------------------------------------------------
eval(Mod, Func, Args) ->
    Debugged = self(),
    Int = dbg_iserver:find(),
    case dbg_iserver:call(Int, {get_meta,Debugged}) of
	{ok,Meta} ->
	    Meta ! {re_entry, Debugged, {eval,{Mod,Func,Args}}},
	    Meta;
	{error,not_interpreted} ->
	    spawn(fun() ->
			  meta(Int, Debugged, Mod, Func, Args)
		  end)
    end.

%%--------------------------------------------------------------------
%% exit_info(Int, AttPid, OrigPid, Reason, ExitInfo)
%%  Int = AttPid = OrigPid = pid()
%%  Reason = term()
%%  ExitInfo = {{Mod,Line}, Bs, Stack} | {}
%% Meta process started when attaching to a terminated process.
%% Spawned (by dbg_iserver) in response to user request.
%%--------------------------------------------------------------------
exit_info(Int, AttPid, OrigPid, Reason, ExitInfo) ->
    put(int, Int),
    put(attached, AttPid),
    put(breakpoints, dbg_iserver:call(Int, all_breaks)),
    put(self, OrigPid),
    put(exit_info, ExitInfo),
    
    case ExitInfo of
	{{Mod,Line},Bs,S} ->
	    Stack = binary_to_term(S),
	    put(stack, Stack),
	    Le = stack_level(Stack),
	    dbg_icmd:tell_attached({exit_at, {Mod, Line}, Reason, Le}),
	    exit_loop(OrigPid, Reason, Bs,#ieval{module=Mod,line=Line});
	{} ->
	    put(stack, []),
	    dbg_icmd:tell_attached({exit_at, null, Reason, 1}),
	    exit_loop(OrigPid, Reason, erl_eval:new_bindings(),#ieval{})
    end.

%%--------------------------------------------------------------------
%% eval_expr(Expr, Bs, Ieval) -> {value, Value, Bs}
%%
%% Evalute a shell expression in the real process.
%% Called (dbg_icmd) in response to a user request.
%%--------------------------------------------------------------------
eval_expr(Expr, Bs, Ieval) ->

    %% Save current exit info
    ExitInfo = get(exit_info),
    Stacktrace = get(stacktrace),

    %% Emulate a surrounding catch
    try debugged_cmd({eval,Expr,Bs}, Bs, Ieval)
    catch
	Class:Reason ->
	    Result = case Class of
			 throw -> Reason;
			 _ -> {'EXIT', Reason}
		     end,

	    %% Reset exit info
	    put(exit_info, ExitInfo),
	    put(stacktrace, Stacktrace),

	    {value, Result, Bs}
    end.

%%--------------------------------------------------------------------
%% check_exit_msg(Msg, Bs, Ieval)
%%   Msg = term()
%% Check if Msg is an 'EXIT' msg from the iserver or a 'DOWN' msg
%% from the debugged process. If so exit with correct reason.
%%--------------------------------------------------------------------
check_exit_msg({'EXIT', Int, Reason}, _Bs, #ieval{level=Le}) ->
    %% This *must* be interpreter which has terminated,
    %% we are not linked to anyone else
    if
	Le==1 ->
	    exit(Reason);
	Le>1 ->
	    exit({Int, Reason})
    end;
check_exit_msg({'DOWN',_,_,_,Reason}, Bs,
	       #ieval{level=Le, module=Mod, line=Li}) ->
    %% This *must* be Debugged which has terminated,
    %% we are not monitoring anyone else

    %% Inform Int about current position, bindings and stack
    ExitInfo =
	case get(exit_info) of

	    %% Debugged has been terminated by someone
	    %% - really the position, bindings and stack are of no
	    %%   importance in this case
	    %% If we don't save them, however, post-mortem analysis
	    %% of the process isn't possible
	    undefined when Le==1 -> % died outside interpreted code
		{};
	    undefined when Le>1 ->
		StackBin = term_to_binary(get(stack)),
		{{Mod, Li}, Bs, StackBin};

	    %% Debugged has terminated due to an exception
	    ExitInfo0 ->
		ExitInfo0
	end,
    dbg_iserver:cast(get(int), {set_exit_info,self(),ExitInfo}),

   if
	Le==1 ->
	    exit(Reason);
	Le>1 ->
	    exit({get(self), Reason})
    end;
check_exit_msg(_Msg, _Bs, _Ieval) ->
    ignore.

%%--------------------------------------------------------------------
%% exception(Class, Reason, Bs, Ieval)
%%   Class = error | exit | throw
%%   Reason = term()
%%   Bs = bindings()
%%   Ieval = #ieval{}
%% Store information about where in the code the error is located
%% and then raise the exception.
%%--------------------------------------------------------------------
exception(Class, Reason, Bs, Ieval) ->
    exception(Class, Reason, fix_stacktrace(1), Bs, Ieval).

exception(Class, Reason, Stacktrace, Bs, #ieval{module=M, line=Line}) ->
    ExitInfo = {{M,Line}, Bs, term_to_binary(get(stack))},
    put(exit_info, ExitInfo),
    put(stacktrace, Stacktrace),
    erlang:Class(Reason).

%%--------------------------------------------------------------------
%% in_use_p(Mod, Cm) -> boolean()
%%   Mod = Cm = atom()
%% Returns true if Mod is found on the stack, otherwise false.
%%--------------------------------------------------------------------
in_use_p(Mod, Mod) -> true;
in_use_p(Mod, _Cm) ->
    case get(trace_stack) of
	false -> true;
	_ -> %  all | no_tail
	    lists:any(fun({_,{M,_,_,_}}) when M =:= Mod -> true;
			 (_) -> false
		      end,
		      get(stack))
    end.

%%====================================================================
%% Internal functions
%%====================================================================

%%--Loops-------------------------------------------------------------

%% Entry point for first-time initialization of meta process
meta(Int, Debugged, M, F, As) ->
    process_flag(trap_exit, true),
    erlang:monitor(process, Debugged),

    %% Inform dbg_iserver, get the initial status in return
    Pargs = case {M, F} of
		%% If it's a fun we're evaluating, show a text
		%% representation of the fun and its arguments,
		%% not dbg_ieval:eval_fun(...)
		{dbg_ieval, eval_fun} ->
		    {Mx, Fx} = lists:last(As),
		    {Mx, Fx, lists:nth(2, As)};
		_ ->
		    {M, F, As}
	    end,
    Status = dbg_iserver:call(Int, {new_process,Debugged,self(),Pargs}),
    
    %% Initiate process dictionary
    put(int, Int),           % pid() dbg_iserver
    put(attached, undefined),% pid() attached process
    put(breakpoints, dbg_iserver:call(Int, all_breaks)),
    put(cache, []),
    put(next_break, Status), % break | running (other values later)
    put(self, Debugged),     % pid() interpreted process
    put(stack, []),
    put(stacktrace, []),
    put(trace_stack, dbg_iserver:call(Int, get_stack_trace)),
    put(trace, false),       % bool() Trace on/off
    put(user_eval, []),


    %% Send the result of the meta process
    Ieval = #ieval{},
    Debugged ! {sys, self(), eval_mfa(Debugged,M,F,As,Ieval)},

    dbg_iserver:cast(Int, {set_status, self(), idle, {}}),
    dbg_icmd:tell_attached(idle),

    meta_loop(Debugged, erl_eval:new_bindings(), Ieval).

debugged_cmd(Cmd, Bs, Ieval) ->
    Debugged = get(self),
    Stacktrace = fix_stacktrace(2),
    Debugged ! {sys, self(), {command,Cmd,Stacktrace}},
    meta_loop(Debugged, Bs, Ieval).

meta_loop(Debugged, Bs, #ieval{level=Le} = Ieval) ->
    receive

	%% The following messages can only be received when Meta is
	%% waiting for Debugged to evaluate non-interpreted code
	%% or a Bif. Le>1
	{sys, Debugged, {value,Val}} ->
	    {value, Val, Bs};
	{sys, Debugged, {value,Val,Bs2}} ->
	    {value, Val, Bs2};
	{sys, Debugged, {exception,{Class,Reason,Stacktrace}}} ->
	    case get(exit_info) of

		%% Error occured outside interpreted code
		undefined ->
		    exception(Class,Reason,Stacktrace,Bs,Ieval);

		%% Error must have occured within a re-entry to
		%% interpreted code, simply raise the exception
		_ ->
		    erlang:Class(Reason)
	    end;

	%% Re-entry to Meta from non-interpreted code
	{re_entry, Debugged, {eval,{M,F,As}}} when Le==1 ->
	    %% Reset process dictionary
	    %% This is really only necessary if the process left
	    %% interpreted code at a call level > 1
	    put(stack, []),
	    put(stacktrace, []),
	    put(exit_info, undefined),
	    
	    dbg_iserver:cast(get(int), {set_status,self(),running,{}}),
	    dbg_icmd:tell_attached(running),

	    %% Tell attached process(es) to update source code.
	    dbg_icmd:tell_attached({re_entry,M,F}),

	    %% Send the result of the meta process
	    Debugged ! {sys,self(),eval_mfa(Debugged,M,F,As,Ieval)},

	    dbg_iserver:cast(get(int), {set_status,self(),idle,{}}),
	    dbg_icmd:tell_attached(idle),
	    meta_loop(Debugged, Bs, Ieval);

	%% Evaluation in Debugged results in call to interpreted
	%% function (probably? a fun)
	{re_entry, Debugged, {eval,{M,F,As}}} when Le>1 ->
	    Ieval2 = Ieval#ieval{module=undefined, line=-1},
	    Debugged ! {sys,self(),eval_mfa(Debugged,M,F,As,Ieval2)},
	    meta_loop(Debugged, Bs, Ieval);

	Msg ->
	    check_exit_msg(Msg, Bs, Ieval),
	    dbg_icmd:handle_msg(Msg, idle, Bs, Ieval),
	    meta_loop(Debugged, Bs, Ieval)
    end.

exit_loop(OrigPid, Reason, Bs, Ieval) ->
    receive
	Msg ->
	    check_exit_msg(Msg, Bs, Ieval),
	    dbg_icmd:handle_msg(Msg, exit_at, Bs, Ieval),
	    exit_loop(OrigPid, Reason, Bs, Ieval)
    end.

%%--Stack emulation---------------------------------------------------

%% We keep track of a call stack that is used for
%%  1) saving stack frames that can be inspected from an Attached
%%     Process GUI (using dbg_icmd:get(Meta, stack_frame, {Dir, SP})
%%  2) generate an approximation of regular stacktrace -- sent to
%%     Debugged when it should raise an exception or evaluate a
%%     function (since it might possible raise an exception)
%%
%% Stack = [Entry]
%%   Entry = {Le, {MFA, Where, Bs}}
%%     Le = int()         % current call level
%%     MFA = {M,F,Args}   % called function (or fun)
%%         | {Fun,Args}   %
%%     Where = {M,Li}     % from where (module+line) function is called
%%     Bs = bindings()    % current variable bindings
%%
%% How to push depends on the "Stack Trace" option (value saved in
%% process dictionary item 'trace_stack').
%%   all - everything is pushed
%%   no_tail - tail recursive push
%%   false - nothing is pushed
%% Whenever a function returns, the corresponding call frame is popped.

push(MFA, Bs, #ieval{level=Le,module=Cm,line=Li,last_call=Lc}) ->
    Entry = {Le, {MFA, {Cm,Li}, Bs}},
    case get(trace_stack) of
	false -> ignore;
	no_tail when Lc ->
	    case get(stack) of
		[] -> put(stack, [Entry]);
		[_Entry|Entries] -> put(stack, [Entry|Entries])
	    end;
	_ -> % all | no_tail when Lc==false
	    put(stack, [Entry|get(stack)])
    end.

pop() ->
    case get(trace_stack) of
	false -> ignore;
	_ -> % all