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authorBjörn Gustavsson <[email protected]>2015-01-29 06:33:52 +0100
committerBjörn Gustavsson <[email protected]>2015-02-03 08:40:49 +0100
commit8c3baeb1275c2e6a316d3b5203e0598906785cdb (patch)
tree15315c8952ba753ab5e97097989e0e7f87e68f34 /lib
parent8c0bebb66ba01b174e6482cd81949eaf08748bcd (diff)
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Suppress warnings for expressions that are assigned to '_'
In c34ad2d5, the compiler learned to silence some warnings for expressions that were explicitly assigned to the '_' variable, as in this example: _ = list_to_integer(S), ok That commit intentionally only made it possible to silence warnings for BIFs that could cause an exception. Warnings would still be produced for: _ = date(), ok because date/0 can never fail and thus making the call completely useless. The reasoning was that such warnings can always be eliminated by eliminating the offending code. While that is true, there is the question about rules and their consistency. It is surprising that '_' can be used to silence some warnings, but has no effect on other warnings. Therefore, we will teach the compiler to silence warnings for the following constructs: * Calls to safe BIFs such as date/0 * Expressions that will cause an exception such as 'X/0' * Terms that are built but not used, such as '{x,X}'
Diffstat (limited to 'lib')
-rw-r--r--lib/compiler/src/sys_core_fold.erl28
-rw-r--r--lib/compiler/src/v3_core.erl45
-rw-r--r--lib/compiler/test/warnings_SUITE.erl44
3 files changed, 79 insertions, 38 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 7066cebb2b..eeb3535936 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -680,23 +680,15 @@ count_bits_1(Int, Bits) -> count_bits_1(Int bsr 64, Bits+64).
%% a rewritten expression consisting of a sequence of
%% the arguments only is returned.
-useless_call(effect, #c_call{anno=Anno,
- module=#c_literal{val=Mod},
+useless_call(effect, #c_call{module=#c_literal{val=Mod},
name=#c_literal{val=Name},
args=Args}=Call) ->
A = length(Args),
case erl_bifs:is_safe(Mod, Name, A) of
false ->
case erl_bifs:is_pure(Mod, Name, A) of
- true ->
- case member(result_not_wanted, Anno) of
- false ->
- add_warning(Call, result_ignored);
- true ->
- ok
- end;
- false ->
- ok
+ true -> add_warning(Call, result_ignored);
+ false -> ok
end,
no;
true ->
@@ -3101,7 +3093,7 @@ add_bin_opt_info(Core, Term) ->
end.
add_warning(Core, Term) ->
- case is_compiler_generated(Core) of
+ case suppress_warning(Core) of
true ->
ok;
false ->
@@ -3126,9 +3118,17 @@ get_file([{file,File}|_]) -> File;
get_file([_|T]) -> get_file(T);
get_file([]) -> "no_file". % should not happen
+suppress_warning(Core) ->
+ is_compiler_generated(Core) orelse
+ is_result_unwanted(Core).
+
is_compiler_generated(Core) ->
- Anno = core_lib:get_anno(Core),
- member(compiler_generated, Anno).
+ Ann = cerl:get_ann(Core),
+ member(compiler_generated, Ann).
+
+is_result_unwanted(Core) ->
+ Ann = cerl:get_ann(Core),
+ member(result_not_wanted, Ann).
get_warnings() ->
ordsets:from_list((erase({?MODULE,warnings}))).
diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index a9b54005d1..f0b90ff31c 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -515,16 +515,16 @@ exprs([], St) -> {[],St}.
%% Generate an internal core expression.
expr({var,L,V}, St) -> {#c_var{anno=lineno_anno(L, St),name=V},[],St};
-expr({char,L,C}, St) -> {#c_literal{anno=lineno_anno(L, St),val=C},[],St};
-expr({integer,L,I}, St) -> {#c_literal{anno=lineno_anno(L, St),val=I},[],St};
-expr({float,L,F}, St) -> {#c_literal{anno=lineno_anno(L, St),val=F},[],St};
-expr({atom,L,A}, St) -> {#c_literal{anno=lineno_anno(L, St),val=A},[],St};
-expr({nil,L}, St) -> {#c_literal{anno=lineno_anno(L, St),val=[]},[],St};
-expr({string,L,S}, St) -> {#c_literal{anno=lineno_anno(L, St),val=S},[],St};
+expr({char,L,C}, St) -> {#c_literal{anno=full_anno(L, St),val=C},[],St};
+expr({integer,L,I}, St) -> {#c_literal{anno=full_anno(L, St),val=I},[],St};
+expr({float,L,F}, St) -> {#c_literal{anno=full_anno(L, St),val=F},[],St};
+expr({atom,L,A}, St) -> {#c_literal{anno=full_anno(L, St),val=A},[],St};
+expr({nil,L}, St) -> {#c_literal{anno=full_anno(L, St),val=[]},[],St};
+expr({string,L,S}, St) -> {#c_literal{anno=full_anno(L, St),val=S},[],St};
expr({cons,L,H0,T0}, St0) ->
{H1,Hps,St1} = safe(H0, St0),
{T1,Tps,St2} = safe(T0, St1),
- A = lineno_anno(L, St2),
+ A = full_anno(L, St2),
{annotate_cons(A, H1, T1, St2),Hps ++ Tps,St2};
expr({lc,L,E,Qs0}, St0) ->
{Qs1,St1} = preprocess_quals(L, Qs0, St0),
@@ -536,7 +536,7 @@ expr({tuple,L,Es0}, St0) ->
A = record_anno(L, St1),
{annotate_tuple(A, Es1, St1),Eps,St1};
expr({map,L,Es0}, St0) ->
- map_build_pairs(#c_literal{val=#{}}, Es0, lineno_anno(L, St0), St0);
+ map_build_pairs(#c_literal{val=#{}}, Es0, full_anno(L, St0), St0);
expr({map,L,M0,Es0}, St0) ->
try expr_map(M0,Es0,lineno_anno(L, St0),St0) of
{_,_,_}=Res -> Res
@@ -551,7 +551,7 @@ expr({map,L,M0,Es0}, St0) ->
args=As},[],St}
end;
expr({bin,L,Es0}, St0) ->
- try expr_bin(Es0, lineno_anno(L, St0), St0) of
+ try expr_bin(Es0, full_anno(L, St0), St0) of
{_,_,_}=Res -> Res
catch
throw:bad_binary ->
@@ -641,11 +641,11 @@ expr({'catch',L,E0}, St0) ->
Lanno = lineno_anno(L, St1),
{#icatch{anno=#a{anno=Lanno},body=Eps ++ [E1]},[],St1};
expr({'fun',L,{function,F,A},{_,_,_}=Id}, St) ->
- Lanno = lineno_anno(L, St),
+ Lanno = full_anno(L, St),
{#c_var{anno=Lanno++[{id,Id}],name={F,A}},[],St};
expr({'fun',L,{function,M,F,A}}, St0) ->
{As,Aps,St1} = safe_list([M,F,A], St0),
- Lanno = lineno_anno(L, St1),
+ Lanno = full_anno(L, St1),
{#icall{anno=#a{anno=Lanno},
module=#c_literal{val=erlang},
name=#c_literal{val=make_fun},
@@ -656,13 +656,9 @@ expr({named_fun,L,'_',Cs,Id}, St) ->
fun_tq(Id, Cs, L, St, unnamed);
expr({named_fun,L,Name,Cs,Id}, St) ->
fun_tq(Id, Cs, L, St, {named,Name});
-expr({call,L,{remote,_,M,F},As0}, #core{wanted=Wanted}=St0) ->
+expr({call,L,{remote,_,M,F},As0}, St0) ->
{[M1,F1|As1],Aps,St1} = safe_list([M,F|As0], St0),
- Lanno = lineno_anno(L, St1),
- Anno = case Wanted of
- false -> [result_not_wanted|Lanno];
- true -> Lanno
- end,
+ Anno = full_anno(L, St1),
{#icall{anno=#a{anno=Anno},module=M1,name=F1,args=As1},Aps,St1};
expr({call,Lc,{atom,Lf,F},As0}, St0) ->
{As1,Aps,St1} = safe_list(As0, St0),
@@ -724,13 +720,13 @@ expr({op,L,'orelse',E1,E2}, St0) ->
expr(E, St);
expr({op,L,Op,A0}, St0) ->
{A1,Aps,St1} = safe(A0, St0),
- LineAnno = lineno_anno(L, St1),
+ LineAnno = full_anno(L, St1),
{#icall{anno=#a{anno=LineAnno}, %Must have an #a{}
module=#c_literal{anno=LineAnno,val=erlang},
name=#c_literal{anno=LineAnno,val=Op},args=[A1]},Aps,St1};
expr({op,L,Op,L0,R0}, St0) ->
{As,Aps,St1} = safe_list([L0,R0], St0),
- LineAnno = lineno_anno(L, St1),
+ LineAnno = full_anno(L, St1),
{#icall{anno=#a{anno=LineAnno}, %Must have an #a{}
module=#c_literal{anno=LineAnno,val=erlang},
name=#c_literal{anno=LineAnno,val=Op},args=As},Aps,St1}.
@@ -971,7 +967,7 @@ fun_tq({_,_,Name}=Id, Cs0, L, St0, NameInfo) ->
{Cs1,Ceps,St1} = clauses(Cs0, St0),
{Args,St2} = new_vars(Arity, St1),
{Ps,St3} = new_vars(Arity, St2), %Need new variables here
- Anno = lineno_anno(L, St3),
+ Anno = full_anno(L, St3),
Fc = function_clause(Ps, Anno, {Name,Arity}),
Fun = #ifun{anno=#a{anno=Anno},
id=[{id,Id}], %We KNOW!
@@ -2341,16 +2337,21 @@ record_anno(L, St) when L >= ?REC_OFFSET ->
true ->
[record | lineno_anno(L - ?REC_OFFSET, St)];
false ->
- lineno_anno(L, St)
+ full_anno(L, St)
end;
record_anno(L, St) when L < -?REC_OFFSET ->
case member(dialyzer, St#core.opts) of
true ->
[record | lineno_anno(L + ?REC_OFFSET, St)];
false ->
- lineno_anno(L, St)
+ full_anno(L, St)
end;
record_anno(L, St) ->
+ full_anno(L, St).
+
+full_anno(L, #core{wanted=false}=St) ->
+ [result_not_wanted|lineno_anno(L, St)];
+full_anno(L, #core{wanted=true}=St) ->
lineno_anno(L, St).
lineno_anno(L, St) ->
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index 6e5a7d35e9..d59c89b264 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -39,7 +39,7 @@
guard/1,bad_arith/1,bool_cases/1,bad_apply/1,
files/1,effect/1,bin_opt_info/1,bin_construction/1,
comprehensions/1,maps/1,redundant_boolean_clauses/1,
- latin1_fallback/1]).
+ latin1_fallback/1,underscore/1]).
% Default timetrap timeout (set in init_per_testcase).
-define(default_timeout, ?t:minutes(2)).
@@ -64,7 +64,8 @@ groups() ->
[pattern,pattern2,pattern3,pattern4,guard,
bad_arith,bool_cases,bad_apply,files,effect,
bin_opt_info,bin_construction,comprehensions,maps,
- redundant_boolean_clauses,latin1_fallback]}].
+ redundant_boolean_clauses,latin1_fallback,
+ underscore]}].
init_per_suite(Config) ->
Config.
@@ -678,6 +679,45 @@ latin1_fallback(Conf) when is_list(Conf) ->
ok.
+underscore(Config) when is_list(Config) ->
+ S0 = <<"f(A) ->
+ _VAR1 = <<A>>,
+ _VAR2 = {ok,A},
+ _VAR3 = [A],
+ ok.
+ g(A) ->
+ _VAR1 = A/0,
+ _VAR2 = date(),
+ ok.
+ h() ->
+ _VAR1 = fun() -> ok end,
+ ok.
+ i(A) ->
+ _VAR1 = #{A=>42},
+ ok.
+ ">>,
+ Ts0 = [{underscore0,
+ S0,
+ [],
+ {warnings,[{2,sys_core_fold,useless_building},
+ {3,sys_core_fold,useless_building},
+ {4,sys_core_fold,useless_building},
+ {7,sys_core_fold,result_ignored},
+ {8,sys_core_fold,{no_effect,{erlang,date,0}}},
+ {11,sys_core_fold,useless_building},
+ {14,sys_core_fold,useless_building}
+ ]}}],
+ [] = run(Config, Ts0),
+
+ %% Replace all "_VAR<digit>" variables with a plain underscore.
+ %% Now there should be no warnings.
+ S1 = re:replace(S0, "_VAR\\d+", "_", [global]),
+ io:format("~s\n", [S1]),
+ Ts1 = [{underscore1,S1,[],[]}],
+ [] = run(Config, Ts1),
+
+ ok.
+
%%%
%%% End of test cases.
%%%