From 8944398e939ce1b8929150118a275d7fb852ac43 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Mon, 6 Aug 2018 14:15:30 +0200
Subject: beam_validator: Fix false diagnostic for a receive nested in a try

When nesting a receive in a try/catch, there could be a false
diagnostic that a fragile term is used.

https://bugs.erlang.org/browse/ERL-684
---
 lib/compiler/src/beam_validator.erl | 26 ++++++++++----------
 lib/compiler/test/receive_SUITE.erl | 49 +++++++++++++++++++++++++++++++++++--
 2 files changed, 60 insertions(+), 15 deletions(-)

(limited to 'lib/compiler')

diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index a1b71251b7..a0eef826ce 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -451,6 +451,19 @@ valfun_1({try_case,Reg}, #vst{current=#st{ct=[Fail|Fails]}}=Vst0) ->
 	Type ->
 	    error({bad_type,Type})
     end;
+valfun_1({get_list,Src,D1,D2}, Vst0) ->
+    assert_type(cons, Src, Vst0),
+    Vst = set_type_reg(term, Src, D1, Vst0),
+    set_type_reg(term, Src, D2, Vst);
+valfun_1({get_hd,Src,Dst}, Vst) ->
+    assert_type(cons, Src, Vst),
+    set_type_reg(term, Src, Dst, Vst);
+valfun_1({get_tl,Src,Dst}, Vst) ->
+    assert_type(cons, Src, Vst),
+    set_type_reg(term, Src, Dst, Vst);
+valfun_1({get_tuple_element,Src,I,Dst}, Vst) ->
+    assert_type({tuple_element,I+1}, Src, Vst),
+    set_type_reg(term, Src, Dst, Vst);
 valfun_1(I, Vst) ->
     valfun_2(I, Vst).
 
@@ -609,19 +622,6 @@ valfun_4({select_val,Src,{f,Fail},{list,Choices}}, Vst) ->
 valfun_4({select_tuple_arity,Tuple,{f,Fail},{list,Choices}}, Vst) ->
     assert_type(tuple, Tuple, Vst),
     kill_state(branch_arities(Choices, Tuple, branch_state(Fail, Vst)));
-valfun_4({get_list,Src,D1,D2}, Vst0) ->
-    assert_type(cons, Src, Vst0),
-    Vst = set_type_reg(term, Src, D1, Vst0),
-    set_type_reg(term, Src, D2, Vst);
-valfun_4({get_hd,Src,Dst}, Vst) ->
-    assert_type(cons, Src, Vst),
-    set_type_reg(term, Src, Dst, Vst);
-valfun_4({get_tl,Src,Dst}, Vst) ->
-    assert_type(cons, Src, Vst),
-    set_type_reg(term, Src, Dst, Vst);
-valfun_4({get_tuple_element,Src,I,Dst}, Vst) ->
-    assert_type({tuple_element,I+1}, Src, Vst),
-    set_type_reg(term, Src, Dst, Vst);
 
 %% New bit syntax matching instructions.
 valfun_4({test,bs_start_match2,{f,Fail},Live,[Ctx,NeedSlots],Ctx}, Vst0) ->
diff --git a/lib/compiler/test/receive_SUITE.erl b/lib/compiler/test/receive_SUITE.erl
index 81ef0d33f2..37e737084a 100644
--- a/lib/compiler/test/receive_SUITE.erl
+++ b/lib/compiler/test/receive_SUITE.erl
@@ -25,7 +25,7 @@
 	 init_per_group/2,end_per_group/2,
 	 init_per_testcase/2,end_per_testcase/2,
 	 export/1,recv/1,coverage/1,otp_7980/1,ref_opt/1,
-	 wait/1]).
+	 wait/1,recv_in_try/1]).
 
 -include_lib("common_test/include/ct.hrl").
 
@@ -44,7 +44,8 @@ all() ->
 
 groups() -> 
     [{p,test_lib:parallel(),
-      [recv,coverage,otp_7980,ref_opt,export,wait]}].
+      [recv,coverage,otp_7980,ref_opt,export,wait,
+       recv_in_try]}].
 
 
 init_per_suite(Config) ->
@@ -305,4 +306,48 @@ wait_1(r, _, _) ->
 wait_1(A, B, C) ->
     {A,B,C}.
 
+recv_in_try(_Config) ->
+    self() ! {ok,fh}, {ok,fh} = recv_in_try(infinity, native),
+    self() ! {ok,ignored}, {ok,42} = recv_in_try(infinity, plain),
+    self() ! {error,ignored}, nok = recv_in_try(infinity, plain),
+    timeout = recv_in_try(1, plain),
+    ok.
+
+recv_in_try(Timeout, Format) ->
+    try
+	receive
+	    {Status,History} ->
+                %% {test,is_tuple,{f,148},[{x,0}]}.
+                %% {test,test_arity,{f,148},[{x,0},2]}.
+                %% {get_tuple_element,{x,0},0,{y,1}}.  %y1 is fragile.
+                %%
+                %% %% Here the fragility of y1 would be be progated to
+                %% %% the 'catch' below. Incorrect, since get_tuple_element
+                %% %% can't fail.
+                %% {get_tuple_element,{x,0},1,{x,2}}.
+                %%
+                %% remove_message.                     %y1 fragility cleared.
+		FH = case Format of
+			native ->
+                             id(History);
+			plain ->
+                             id(42)
+		    end,
+		case Status of
+		    ok ->
+			{ok,FH};
+		    error ->
+			nok
+		end
+	after Timeout ->
+		timeout
+	end
+    catch
+        %% The fragility of y1 incorrectly propagated to here.
+        %% beam_validator would complain.
+	throw:{error,Reason} ->
+	    {nok,Reason}
+    end.
+
+
 id(I) -> I.
-- 
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