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authorBjörn Gustavsson <[email protected]>2017-11-14 09:05:31 +0100
committerBjörn Gustavsson <[email protected]>2017-11-30 12:46:51 +0100
commitef2e55c707a6c3d1f54f2acb9c8bfbe3fb7a8659 (patch)
tree7a9eae08bd786efbebddb53763888a66ed580abb /lib/stdlib
parent0c4574cc31414a5204eabfad7eb0ac5095c0ace1 (diff)
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Add syntax in try/catch to retrieve the stacktrace directly
This commit adds a new syntax for retrieving the stacktrace without calling erlang:get_stacktrace/0. That allow us to deprecate erlang:get_stacktrace/0 and ultimately remove it. The problem with erlang:get_stacktrace/0 is that it can keep huge terms in a process for an indefinite time after an exception. The stacktrace can be huge after a 'function_clause' exception or a failed call to a BIF or operator, because the arguments for the call will be included in the stacktrace. For example: 1> catch abs(lists:seq(1, 1000)). {'EXIT',{badarg,[{erlang,abs, [[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20|...]], []}, {erl_eval,do_apply,6,[{file,"erl_eval.erl"},{line,674}]}, {erl_eval,expr,5,[{file,"erl_eval.erl"},{line,431}]}, {shell,exprs,7,[{file,"shell.erl"},{line,687}]}, {shell,eval_exprs,7,[{file,"shell.erl"},{line,642}]}, {shell,eval_loop,3,[{file,"shell.erl"},{line,627}]}]}} 2> erlang:get_stacktrace(). [{erlang,abs, [[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22, 23,24|...]], []}, {erl_eval,do_apply,6,[{file,"erl_eval.erl"},{line,674}]}, {erl_eval,expr,5,[{file,"erl_eval.erl"},{line,431}]}, {shell,exprs,7,[{file,"shell.erl"},{line,687}]}, {shell,eval_exprs,7,[{file,"shell.erl"},{line,642}]}, {shell,eval_loop,3,[{file,"shell.erl"},{line,627}]}] 3> We can extend the syntax for clauses in try/catch to optionally bind the stacktrace to a variable. Here is an example using the current syntax: try Expr catch C:E -> Stk = erlang:get_stacktrace(), . . . In the new syntax, it would look like: try Expr catch C:E:Stk -> . . . Only a variable (not a pattern) is allowed in the stacktrace position, to discourage matching of the stacktrace. (Matching would also be expensive, because the raw format of the stacktrace would have to be converted to the cooked form before matching.) Note that: try Expr catch E -> . . . is a shorthand for: try Expr catch throw:E -> . . . If the stacktrace is to be retrieved for a throw, the 'throw:' prefix must be explicitly included: try Expr catch throw:E:Stk -> . . .
Diffstat (limited to 'lib/stdlib')
-rw-r--r--lib/stdlib/src/erl_lint.erl44
-rw-r--r--lib/stdlib/src/erl_parse.yrl12
-rw-r--r--lib/stdlib/test/erl_lint_SUITE.erl39
3 files changed, 80 insertions, 15 deletions
diff --git a/lib/stdlib/src/erl_lint.erl b/lib/stdlib/src/erl_lint.erl
index f58cb35cea..1930c462e8 100644
--- a/lib/stdlib/src/erl_lint.erl
+++ b/lib/stdlib/src/erl_lint.erl
@@ -144,6 +144,7 @@ value_option(Flag, Default, On, OnVal, Off, OffVal, Opts) ->
:: dict:dict(ta(), #typeinfo{}),
exp_types=gb_sets:empty() %Exported types
:: gb_sets:set(ta()),
+ in_try_head=false :: boolean(), %In a try head.
catch_scope = none %Inside/outside try or catch
:: catch_scope()
}).
@@ -312,6 +313,10 @@ format_error({unused_var, V}) ->
io_lib:format("variable ~w is unused", [V]);
format_error({variable_in_record_def,V}) ->
io_lib:format("variable ~w in record definition", [V]);
+format_error({stacktrace_guard,V}) ->
+ io_lib:format("stacktrace variable ~w must not be used in a guard", [V]);
+format_error({stacktrace_bound,V}) ->
+ io_lib:format("stacktrace variable ~w must not be previously bound", [V]);
%% --- binaries ---
format_error({undefined_bittype,Type}) ->
io_lib:format("bit type ~tw undefined", [Type]);
@@ -3218,11 +3223,11 @@ is_module_dialyzer_option(Option) ->
try_clauses(Scs, Ccs, In, Vt, St0) ->
{Csvt0,St1} = icrt_clauses(Scs, Vt, St0),
- St2 = St1#lint{catch_scope=try_catch},
+ St2 = St1#lint{catch_scope=try_catch,in_try_head=true},
{Csvt1,St3} = icrt_clauses(Ccs, Vt, St2),
Csvt = Csvt0 ++ Csvt1,
UpdVt = icrt_export(Csvt, Vt, In, St3),
- {UpdVt,St3}.
+ {UpdVt,St3#lint{in_try_head=false}}.
%% icrt_clauses(Clauses, In, ImportVarTable, State) ->
%% {UpdVt,State}.
@@ -3239,12 +3244,29 @@ icrt_clauses(Cs, Vt, St) ->
mapfoldl(fun (C, St0) -> icrt_clause(C, Vt, St0) end, St, Cs).
icrt_clause({clause,_Line,H,G,B}, Vt0, #lint{catch_scope=Scope}=St0) ->
- {Hvt,Binvt,St1} = head(H, Vt0, St0),
- Vt1 = vtupdate(Hvt, Binvt),
- {Gvt,St2} = guard(G, vtupdate(Vt1, Vt0), St1),
- Vt2 = vtupdate(Gvt, Vt1),
- {Bvt,St3} = exprs(B, vtupdate(Vt2, Vt0), St2),
- {vtupdate(Bvt, Vt2),St3#lint{catch_scope=Scope}}.
+ Vt1 = taint_stack_var(Vt0, H, St0),
+ {Hvt,Binvt,St1} = head(H, Vt1, St0),
+ Vt2 = vtupdate(Hvt, Binvt),
+ Vt3 = taint_stack_var(Vt2, H, St0),
+ {Gvt,St2} = guard(G, vtupdate(Vt3, Vt0), St1#lint{in_try_head=false}),
+ Vt4 = vtupdate(Gvt, Vt2),
+ {Bvt,St3} = exprs(B, vtupdate(Vt4, Vt0), St2),
+ {vtupdate(Bvt, Vt4),St3#lint{catch_scope=Scope}}.
+
+taint_stack_var(Vt, Pat, #lint{in_try_head=true}) ->
+ [{tuple,_,[_,_,{var,_,Stk}]}] = Pat,
+ case Stk of
+ '_' ->
+ Vt;
+ _ ->
+ lists:map(fun({V,{bound,Used,Lines}}) when V =:= Stk ->
+ {V,{stacktrace,Used,Lines}};
+ (B) ->
+ B
+ end, Vt)
+ end;
+taint_stack_var(Vt, _Pat, #lint{in_try_head=false}) ->
+ Vt.
icrt_export(Vts, Vt, {Tag,Attrs}, St) ->
{_File,Loc} = loc(Attrs, St),
@@ -3484,6 +3506,9 @@ pat_var(V, Line, Vt, Bvt, St) ->
{[{V,{bound,used,Ls}}],[],
%% As this is matching, exported vars are risky.
add_warning(Line, {exported_var,V,From}, St)};
+ {ok,{stacktrace,_Usage,Ls}} ->
+ {[{V,{bound,used,Ls}}],[],
+ add_error(Line, {stacktrace_bound,V}, St)};
error when St#lint.recdef_top ->
{[],[{V,{bound,unused,[Line]}}],
add_error(Line, {variable_in_record_def,V}, St)};
@@ -3541,6 +3566,9 @@ expr_var(V, Line, Vt, St) ->
false ->
{[{V,{{export,From},used,Ls}}],St}
end;
+ {ok,{stacktrace,_Usage,Ls}} ->
+ {[{V,{bound,used,Ls}}],
+ add_error(Line, {stacktrace_guard,V}, St)};
error ->
{[{V,{bound,used,[Line]}}],
add_error(Line, {unbound_var,V}, St)}
diff --git a/lib/stdlib/src/erl_parse.yrl b/lib/stdlib/src/erl_parse.yrl
index 298d96834b..14ca24362e 100644
--- a/lib/stdlib/src/erl_parse.yrl
+++ b/lib/stdlib/src/erl_parse.yrl
@@ -41,7 +41,7 @@ record_expr record_tuple record_field record_fields
map_expr map_tuple map_field map_field_assoc map_field_exact map_fields map_key
if_expr if_clause if_clauses case_expr cr_clause cr_clauses receive_expr
fun_expr fun_clause fun_clauses atom_or_var integer_or_var
-try_expr try_catch try_clause try_clauses
+try_expr try_catch try_clause try_clauses try_opt_stacktrace
function_call argument_list
exprs guard
atomic strings
@@ -504,13 +504,15 @@ try_clauses -> try_clause ';' try_clauses : ['$1' | '$3'].
try_clause -> pat_expr clause_guard clause_body :
A = ?anno('$1'),
{clause,A,[{tuple,A,[{atom,A,throw},'$1',{var,A,'_'}]}],'$2','$3'}.
-try_clause -> atom ':' pat_expr clause_guard clause_body :
+try_clause -> atom ':' pat_expr try_opt_stacktrace clause_guard clause_body :
A = ?anno('$1'),
- {clause,A,[{tuple,A,['$1','$3',{var,A,'_'}]}],'$4','$5'}.
-try_clause -> var ':' pat_expr clause_guard clause_body :
+ {clause,A,[{tuple,A,['$1','$3',{var,A,'$4'}]}],'$5','$6'}.
+try_clause -> var ':' pat_expr try_opt_stacktrace clause_guard clause_body :
A = ?anno('$1'),
- {clause,A,[{tuple,A,['$1','$3',{var,A,'_'}]}],'$4','$5'}.
+ {clause,A,[{tuple,A,['$1','$3',{var,A,'$4'}]}],'$5','$6'}.
+try_opt_stacktrace -> ':' var : element(3, '$2').
+try_opt_stacktrace -> '$empty' : '_'.
argument_list -> '(' ')' : {[],?anno('$1')}.
argument_list -> '(' exprs ')' : {'$2',?anno('$1')}.
diff --git a/lib/stdlib/test/erl_lint_SUITE.erl b/lib/stdlib/test/erl_lint_SUITE.erl
index b76bece07f..5efffc6a5c 100644
--- a/lib/stdlib/test/erl_lint_SUITE.erl
+++ b/lib/stdlib/test/erl_lint_SUITE.erl
@@ -66,7 +66,8 @@
otp_11851/1,otp_11879/1,otp_13230/1,
record_errors/1, otp_11879_cont/1,
non_latin1_module/1, otp_14323/1,
- get_stacktrace/1, otp_14285/1, otp_14378/1]).
+ get_stacktrace/1, stacktrace_syntax/1,
+ otp_14285/1, otp_14378/1]).
suite() ->
[{ct_hooks,[ts_install_cth]},
@@ -87,7 +88,7 @@ all() ->
maps, maps_type, maps_parallel_match,
otp_11851, otp_11879, otp_13230,
record_errors, otp_11879_cont, non_latin1_module, otp_14323,
- get_stacktrace, otp_14285, otp_14378].
+ get_stacktrace, stacktrace_syntax, otp_14285, otp_14378].
groups() ->
[{unused_vars_warn, [],
@@ -4129,6 +4130,40 @@ get_stacktrace(Config) ->
run(Config, Ts),
ok.
+stacktrace_syntax(Config) ->
+ Ts = [{guard,
+ <<"t1() ->
+ try error(foo)
+ catch _:_:Stk when is_number(Stk) -> ok
+ end.
+ ">>,
+ [],
+ {errors,[{3,erl_lint,{stacktrace_guard,'Stk'}}],[]}},
+ {bound,
+ <<"t1() ->
+ Stk = [],
+ try error(foo)
+ catch _:_:Stk -> ok
+ end.
+ ">>,
+ [],
+ {errors,[{4,erl_lint,{stacktrace_bound,'Stk'}}],[]}},
+ {guard_and_bound,
+ <<"t1() ->
+ Stk = [],
+ try error(foo)
+ catch _:_:Stk when is_integer(Stk) -> ok
+ end.
+ ">>,
+ [],
+ {errors,[{4,erl_lint,{stacktrace_bound,'Stk'}},
+ {4,erl_lint,{stacktrace_guard,'Stk'}}],[]}}
+ ],
+
+ run(Config, Ts),
+ ok.
+
+
%% Unicode atoms.
otp_14285(Config) ->
%% A small sample of all the errors and warnings in module erl_lint.