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authorBjörn Gustavsson <[email protected]>2016-02-08 07:06:31 +0100
committerBjörn Gustavsson <[email protected]>2016-02-08 08:08:55 +0100
commitabde1d03db03536af19fdb274f1119bbfaba262b (patch)
treefc7eb2311be3f3aa458fb298a5a23803b7bbfe67 /lib/compiler/src
parenta03b7add86b92d0d7d2d744e5555314bedbc2197 (diff)
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Eliminate crash because of unsafe delaying of sub-binary creation
The following code would fail to compile: decode(<<Code/integer, Bin/binary>>) -> <<C1/integer, B1/binary>> = Bin, case C1 of X when X =:= 1 orelse X =:= 2 -> Bin2 = <<>>; _ -> Bin2 = B1 end, case Code of 1 -> decode(Bin2); _ -> Bin2 end. The error message would be: t: function decode/1+28: Internal consistency check failed - please report this bug. Instruction: return Error: {match_context,{x,0}}: The beam_bsm pass would delay the creation of a sub-binary when it was unsafe to do so. The culprit was the btb_follow_branch/3 function that for performance reasons cached labels that had already been checked. The problem was the safety of a label also depends on the contents of the registers. Therefore, the key for caching needs to be both the label and the register contents. Reported-by: José Valim
Diffstat (limited to 'lib/compiler/src')
-rw-r--r--lib/compiler/src/beam_bsm.erl5
1 files changed, 3 insertions, 2 deletions
diff --git a/lib/compiler/src/beam_bsm.erl b/lib/compiler/src/beam_bsm.erl
index 4f76350269..62356928ae 100644
--- a/lib/compiler/src/beam_bsm.erl
+++ b/lib/compiler/src/beam_bsm.erl
@@ -421,7 +421,8 @@ btb_follow_branches([], _, D) -> D.
btb_follow_branch(0, _Regs, D) -> D;
btb_follow_branch(Lbl, Regs, #btb{ok_br=Br0,index=Li}=D) ->
- case gb_sets:is_member(Lbl, Br0) of
+ Key = {Lbl,Regs},
+ case gb_sets:is_member(Key, Br0) of
true ->
%% We have already followed this branch and it was OK.
D;
@@ -432,7 +433,7 @@ btb_follow_branch(Lbl, Regs, #btb{ok_br=Br0,index=Li}=D) ->
btb_reaches_match_1(Is, Regs, D),
%% Since we got back, this branch is OK.
- D#btb{ok_br=gb_sets:insert(Lbl, Br),must_not_save=MustNotSave,
+ D#btb{ok_br=gb_sets:insert(Key, Br),must_not_save=MustNotSave,
must_save=MustSave}
end.