From a3ec2644f58d8cfeca0240929d44885ff7a517fa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 26 Apr 2016 09:11:07 +0200
Subject: v3_core: Don't depend on sys_core_fold for cleaning up

v3_core would generate unsafe code for the following example:

  f() ->
    {ok={error,E}} = foo(),
    E.

Internally, the code would look similar to:

  f() ->
    Var = foo(),
    error({badmatch,Var}),
    E.

That is, there would remain a reference to an unbound variable.
Normally, sys_core_fold would remove the reference to 'E', but if
if optimization was disabled the compiler would crash.
---
 lib/compiler/src/v3_core.erl      | 23 ++++++++++++++++++-----
 lib/compiler/test/match_SUITE.erl |  7 +++++++
 2 files changed, 25 insertions(+), 5 deletions(-)

(limited to 'lib')

diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 3299149457..83b3650180 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -510,8 +510,16 @@ unforce(_, Vs) -> Vs.
 
 exprs([E0|Es0], St0) ->
     {E1,Eps,St1} = expr(E0, St0),
-    {Es1,St2} = exprs(Es0, St1),
-    {Eps ++ [E1] ++ Es1,St2};
+    case E1 of
+	#iprimop{name=#c_literal{val=match_fail}} ->
+	    %% Must discard the rest of the body, because it
+	    %% may refer to variables that have not been bound.
+	    %% Example: {ok={error,E}} = foo(), E.
+	    {Eps ++ [E1],St1};
+	_ ->
+	    {Es1,St2} = exprs(Es0, St1),
+	    {Eps ++ [E1] ++ Es1,St2}
+    end;
 exprs([], St) -> {[],St}.
 
 %% expr(Expr, State) -> {Cexpr,[PreExp],State}.
@@ -681,9 +689,14 @@ expr({match,L,P0,E0}, St0) ->
     Fc = fail_clause([Fpat], Lanno, c_tuple([#c_literal{val=badmatch},Fpat])),
     case P2 of
 	nomatch ->
-	    St = add_warning(L, nomatch, St5),
-	    {#icase{anno=#a{anno=Lanno},
-		    args=[E2],clauses=[],fc=Fc},Eps1++Eps2,St};
+	    St6 = add_warning(L, nomatch, St5),
+	    {Expr,Eps3,St} = safe(E1, St6),
+	    Eps = Eps1 ++ Eps2 ++ Eps3,
+	    Badmatch = c_tuple([#c_literal{val=badmatch},Expr]),
+	    Fail = #iprimop{anno=#a{anno=Lanno},
+			    name=#c_literal{val=match_fail},
+			    args=[Badmatch]},
+	    {Fail,Eps,St};
 	Other when not is_atom(Other) ->
 	    {#imatch{anno=#a{anno=Lanno},pat=P2,arg=E2,fc=Fc},Eps1++Eps2,St5}
     end;
diff --git a/lib/compiler/test/match_SUITE.erl b/lib/compiler/test/match_SUITE.erl
index 45d84a7b80..92a9802cad 100644
--- a/lib/compiler/test/match_SUITE.erl
+++ b/lib/compiler/test/match_SUITE.erl
@@ -150,6 +150,9 @@ aliases(Config) when is_list(Config) ->
     none = mixed_aliases({a,42}),
     none = mixed_aliases(42),
 
+    %% Non-matching aliases.
+    {'EXIT',{{badmatch,42},_}} = (catch nomatch_alias(42)),
+
     ok.
 
 str_alias(V) ->
@@ -259,6 +262,10 @@ mixed_aliases(<<X:8>> = {a,X}) -> {c,X};
 mixed_aliases([X] = <<X:8>>) -> {d,X};
 mixed_aliases(_) -> none.
 
+nomatch_alias(I) ->
+    {ok={A,B}} = id(I),
+    {A,B}.
+
 %% OTP-7018.
 
 match_in_call(Config) when is_list(Config) ->
-- 
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