From 121cc9ba61e44e9c47d831d837dfb0f0b2d81990 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 17 May 2016 07:09:59 +0200
Subject: beam_type: Eliminate crash

The following code:

simple() ->
    case try 0 after [] end of
	0 -> college;
	1 -> 0
    end.

would crash the compiler like this:

crash reason: {case_clause,
    {'EXIT',
        {function_clause,
            [{beam_type,simplify_select_val_int,
                 [{select,select_val,
                      {x,0},
                      {f,7},
                      [{integer,1},{f,9},{integer,0},{f,8}]},
                  0],
                 [{file,"beam_type.erl"},{line,169}]},
             {beam_type,simplify_basic_1,3,
                 [{file,"beam_type.erl"},{line,155}]},
             {beam_type,opt,3,[{file,"beam_type.erl"},{line,57}]},
             {beam_type,function,1,[{file,"beam_type.erl"},{line,36}]},
             {beam_type,'-module/2-lc$^0/1-0-',1,
                 [{file,"beam_type.erl"},{line,30}]},
             {beam_type,module,2,[{file,"beam_type.erl"},{line,30}]},
             {compile,'-select_passes/2-anonymous-2-',2,
                 [{file,"compile.erl"},{line,521}]},
             {compile,'-internal_comp/4-anonymous-1-',2,
                 [{file,"compile.erl"},{line,306}]}]}}}

The root cause is that the type representation is not well-defined.

Integers could be represented in three different ways:

  integer
  {integer,{1,10}}
  {integer,0}

However, only the first two forms were handled.

To avoid similar problems in the future:

* Make the type representation stricter. Make sure that integers are
  only represented as 'integer' or {integer,{Min,Max}}.

* Call verify_type/1 whenever a new type is added (not only when
  merging types) to ensure that only the supported types are added
  to the type database).

(ERL-150)
---
 lib/compiler/test/beam_type_SUITE.erl | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

(limited to 'lib/compiler/test')

diff --git a/lib/compiler/test/beam_type_SUITE.erl b/lib/compiler/test/beam_type_SUITE.erl
index 063a27ad8d..69e2f1838d 100644
--- a/lib/compiler/test/beam_type_SUITE.erl
+++ b/lib/compiler/test/beam_type_SUITE.erl
@@ -21,7 +21,8 @@
 
 -export([all/0,suite/0,groups/0,init_per_suite/1,end_per_suite/1,
 	 init_per_group/2,end_per_group/2,
-	 integers/1,coverage/1,booleans/1,setelement/1]).
+	 integers/1,coverage/1,booleans/1,setelement/1,cons/1,
+	 tuple/1]).
 
 suite() -> [{ct_hooks,[ts_install_cth]}].
 
@@ -34,7 +35,9 @@ groups() ->
       [integers,
        coverage,
        booleans,
-       setelement
+       setelement,
+       cons,
+       tuple
       ]}].
 
 init_per_suite(Config) ->
@@ -56,6 +59,8 @@ integers(_Config) ->
     a = do_integers_2(<<0:1>>),
     {'EXIT',{{case_clause,-1},_}} = (catch do_integers_2(<<1:1>>)),
 
+    college = do_integers_3(),
+
     ok.
 
 do_integers_1(B0) ->
@@ -72,6 +77,12 @@ do_integers_2(Bin) ->
 	1 -> b
     end.
 
+do_integers_3() ->
+    case try 0 after [] end of
+	0 -> college;
+	1 -> 0
+    end.
+
 coverage(_Config) ->
     {'EXIT',{badarith,_}} = (catch id(1) bsl 0.5),
     {'EXIT',{badarith,_}} = (catch id(2.0) bsl 2),
@@ -101,5 +112,19 @@ setelement(_Config) ->
     {b,_} = setelement(1, T0, b),
     ok.
 
+cons(_Config) ->
+    [did] = cons(assigned, did),
+    ok.
+
+cons(assigned, Instrument) ->
+    [Instrument] = [did].
+
+tuple(_Config) ->
+    {'EXIT',{{badmatch,{necessary}},_}} = (catch do_tuple()),
+    ok.
+
+do_tuple() ->
+    {0, _} = {necessary}.
+
 id(I) ->
     I.
-- 
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