From 1899aa487d898078e6e7b1c6b7ea3aa5ea31c7e5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Thu, 19 Feb 2015 13:34:22 +0100
Subject: beam_jump: Don't jump into the middle of a 'try'

The code sharing optimization could produce a jump into the
middle of a 'try' block. beam_validator would reject the code.

Reported-by: Ulf Norell
---
 lib/compiler/src/beam_jump.erl | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

(limited to 'lib/compiler/src/beam_jump.erl')

diff --git a/lib/compiler/src/beam_jump.erl b/lib/compiler/src/beam_jump.erl
index 4e699c4fbf..f457aa1155 100644
--- a/lib/compiler/src/beam_jump.erl
+++ b/lib/compiler/src/beam_jump.erl
@@ -166,6 +166,12 @@ share_1([{label,L}=Lbl|Is], Dict0, Seq, Acc) ->
     end;
 share_1([{func_info,_,_,_}=I|Is], _, [], Acc) ->
     reverse(Is, [I|Acc]);
+share_1([{'try',_,_}=I|Is], Dict0, Seq, Acc) ->
+    Dict = clean_non_sharable(Dict0),
+    share_1(Is, Dict, [I|Seq], Acc);
+share_1([{try_case,_}=I|Is], Dict0, Seq, Acc) ->
+    Dict = clean_non_sharable(Dict0),
+    share_1(Is, Dict, [I|Seq], Acc);
 share_1([I|Is], Dict, Seq, Acc) ->
     case is_unreachable_after(I) of
 	false ->
@@ -174,6 +180,24 @@ share_1([I|Is], Dict, Seq, Acc) ->
 	    share_1(Is, Dict, [I], Acc)
     end.
 
+clean_non_sharable(Dict) ->
+    %% We are passing in or out of a 'try' block. Remove
+    %% sequences that should not shared over the boundaries
+    %% of a 'try' block. Since the end of the sequence must match,
+    %% the only possible match between a sequence outside and
+    %% a sequence inside the 'try' block is a sequence that ends
+    %% with an instruction that causes an exception. Any sequence
+    %% that causes an exception must contain a line/1 instruction.
+    dict:filter(fun(K, _V) -> sharable_with_try(K) end, Dict).
+
+sharable_with_try([{line,_}|_]) ->
+    %% This sequence may cause an exception and may potentially
+    %% match a sequence on the other side of the 'try' block
+    %% boundary.
+    false;
+sharable_with_try([_|Is]) ->
+    sharable_with_try(Is);
+sharable_with_try([]) -> true.
 
 %% Eliminate all fallthroughs. Return the result reversed.
 
-- 
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