From 7b169140b2d37f43996b9d1a94877926a471d97d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Tue, 2 May 2017 05:41:17 +0200 Subject: Warn for potentially unsafe use of get_stacktrace/0 erlang:get_stacktrace/0 returns the stacktrace for the latest exception. The problem is that the stacktrace is kept until the next exception occurs. If the last exception was a 'function_clause' or a 'badarg', the arguments for the call are also kept forever. The arguments can be terms of any size (potentially huge). In a future release, we would like to only allow erlang:get_stacktrace/0 from within a 'try' expression. That would make it possible to clear the stacktrace when the 'try' expression is exited. The 'catch' expression has no natural end where the stacktrace could be cleared. The stacktrace could be cleared at the end of the function that the 'catch' occurs in, but that would cause problems in the following scenario (from real life, but simplified): try ... catch _:_ -> io:format(...), io:format("~p\n", [erlang:get_stacktrace()]) end. %% In io.erl. format(Fmt, Args) -> Res = case ... of SomePattern -> catch... ...; SomeOtherPattern -> %% Output the formatted string here ... end, clear_stacktrace(), %% Inserted by compiler. Res. The call to io:format() would always clear the stacktrace before it could be retrieved. That problem could be solved by tightning the scope in which the stacktrace is kept, but the rules for how long erlang:get_stacktrace/0 would work would become complicated. Therefore, the solution we suggest for a future major release of OTP is that erlang:get_stacktrace/0 will return [] if it is called outside the 'catch' part of a 'try' expression. To help users prepare, introduce a warning when it is likely that erlang:get_stacktrace/0 will always return an empty list, for example in this code: catch error(foo), Stk = erlang:get_stacktrace() or in this code: try Expr catch _:_ -> ok end, Stk = erlang:get_stacktrace() --- lib/stdlib/test/erl_lint_SUITE.erl | 63 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 61 insertions(+), 2 deletions(-) (limited to 'lib/stdlib/test') diff --git a/lib/stdlib/test/erl_lint_SUITE.erl b/lib/stdlib/test/erl_lint_SUITE.erl index 03cad2c093..02524679fa 100644 --- a/lib/stdlib/test/erl_lint_SUITE.erl +++ b/lib/stdlib/test/erl_lint_SUITE.erl @@ -65,7 +65,8 @@ maps/1,maps_type/1,maps_parallel_match/1, otp_11851/1,otp_11879/1,otp_13230/1, record_errors/1, otp_11879_cont/1, - non_latin1_module/1, otp_14323/1]). + non_latin1_module/1, otp_14323/1, + get_stacktrace/1]). suite() -> [{ct_hooks,[ts_install_cth]}, @@ -85,7 +86,8 @@ all() -> too_many_arguments, basic_errors, bin_syntax_errors, predef, maps, maps_type, maps_parallel_match, otp_11851, otp_11879, otp_13230, - record_errors, otp_11879_cont, non_latin1_module, otp_14323]. + record_errors, otp_11879_cont, non_latin1_module, otp_14323, + get_stacktrace]. groups() -> [{unused_vars_warn, [], @@ -3980,6 +3982,63 @@ otp_14323(Config) -> [] = run(Config, Ts), ok. +get_stacktrace(Config) -> + Ts = [{old_catch, + <<"t1() -> + catch error(foo), + erlang:get_stacktrace(). + ">>, + [], + {warnings,[{3,erl_lint,{get_stacktrace,after_old_catch}}]}}, + {nowarn_get_stacktrace, + <<"t1() -> + catch error(foo), + erlang:get_stacktrace(). + ">>, + [nowarn_get_stacktrace], + []}, + {try_catch, + <<"t1(X) -> + try abs(X) of + _ -> + erlang:get_stacktrace() + catch + _:_ -> ok + end. + + t2() -> + try error(foo) + catch _:_ -> ok + end, + erlang:get_stacktrace(). + + t3() -> + try error(foo) + catch _:_ -> + try error(bar) + catch _:_ -> + ok + end, + erlang:get_stacktrace() + end. + + no_warning(X) -> + try + abs(X) + catch + _:_ -> + erlang:get_stacktrace() + end. + ">>, + [], + {warnings,[{4,erl_lint,{get_stacktrace,wrong_part_of_try}}, + {13,erl_lint,{get_stacktrace,after_try}}, + {22,erl_lint,{get_stacktrace,after_try}}]}}], + + run(Config, Ts), + ok. + + run(Config, Tests) -> F = fun({N,P,Ws,E}, BadL) -> case catch run_test(Config, P, Ws) of -- cgit v1.2.3 From b57e89092409193457aa2ad026c895d5559d428d Mon Sep 17 00:00:00 2001 From: Hans Bolinder Date: Mon, 15 May 2017 14:16:52 +0200 Subject: stdlib: Add io_lib:limit_term/2 The term returned by io_lib:limit_term(Term, Depth) should return the same string if substituted for Term in io_lib:format("~P", [Term, Depth]) or io_lib:format("~W", [Term, Depth]). --- lib/stdlib/test/io_SUITE.erl | 59 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 57 insertions(+), 2 deletions(-) (limited to 'lib/stdlib/test') diff --git a/lib/stdlib/test/io_SUITE.erl b/lib/stdlib/test/io_SUITE.erl index ef3f0be5d7..e2c73371cd 100644 --- a/lib/stdlib/test/io_SUITE.erl +++ b/lib/stdlib/test/io_SUITE.erl @@ -31,7 +31,7 @@ otp_10836/1, io_lib_width_too_small/1, io_with_huge_message_queue/1, format_string/1, maps/1, coverage/1, otp_14178_unicode_atoms/1, otp_14175/1, - otp_14285/1]). + otp_14285/1, limit_term/1]). -export([pretty/2]). @@ -63,7 +63,7 @@ all() -> io_lib_print_binary_depth_one, otp_10302, otp_10755, otp_10836, io_lib_width_too_small, io_with_huge_message_queue, format_string, maps, coverage, otp_14178_unicode_atoms, otp_14175, - otp_14285]. + otp_14285, limit_term]. %% Error cases for output. error_1(Config) when is_list(Config) -> @@ -2373,3 +2373,58 @@ otp_14285(_Config) -> latin1_fmt(Fmt, Args) -> L = fmt(Fmt, Args), true = lists:all(fun is_latin1/1, L). + +limit_term(_Config) -> + {_, 2} = limt([a,b,c], 2), + {_, 2} = limt([a,b,c], 3), + {_, 2} = limt([a,b|c], 2), + {_, 2} = limt([a,b|c], 3), + {_, 2} = limt({a,b,c,[d,e]}, 2), + {_, 2} = limt({a,b,c,[d,e]}, 3), + {_, 2} = limt({a,b,c,[d,e]}, 4), + {_, 1} = limt(<<"foo">>, 18), + ok = blimt(<<"123456789012345678901234567890">>), + {_, 1} = limt(<<7:3>>, 2), + {_, 1} = limt(<<7:21>>, 2), + {_, 1} = limt([], 2), + {_, 1} = limt({}, 2), + {_, 1} = limt(#{}, 2), + {_, 1} = limt(#{[] => {}}, 2), + {_, 1} = limt(#{[] => {}}, 3), + T = #{[] => {},[a] => [b]}, + {_, 1} = limt(T, 2), + {_, 1} = limt(T, 3), + {_, 1} = limt(T, 4), + ok. + +blimt(Binary) -> + blimt(Binary, byte_size(Binary)). + +blimt(_B, 1) -> ok; +blimt(B, D) -> + {_, 1} = limt(B, D), + blimt(B, D - 1). + +limt(Term, Depth) when is_integer(Depth) -> + T1 = io_lib:limit_term(Term, Depth), + S = form(Term, Depth), + S1 = form(T1, Depth), + OK1 = S1 =:= S, + + T2 = io_lib:limit_term(Term, Depth+1), + S2 = form(T2, Depth), + OK2 = S2 =:= S, + + T3 = io_lib:limit_term(Term, Depth-1), + S3 = form(T3, Depth), + OK3 = S3 =/= S, + + R = case {OK1, OK2, OK3} of + {true, true, true} -> 2; + {true, true, false} -> 1; + _ -> 0 + end, + {{S, S1, S2}, R}. + +form(Term, Depth) -> + lists:flatten(io_lib:format("~W", [Term, Depth])). -- cgit v1.2.3