compiler: Eliminate internal consistency failure in binary matching

The following code:

  check(<<"string">>, a1) ->
    one;
  check(_, a2) ->
    two;
  check(undefined, a3) ->
    three.

produces an internal consistency failure:

  check: function check/2+17:
    Internal consistency check failed - please report this bug.
    Instruction: {test,is_eq_exact,{f,7},[{x,0},{atom,undefined}]}
    Error:       {match_context,{x,0}}:

Actually, in the current implementation of the run-time system,
comparing a match context to an atom is safe, so I briefly considered
updating the beam_validator to let this code pass through. I
abandoned that approach because not all terms would be safe to
compare to a match context, and the implementation might change
in the future.

Therefore, fix this problem by not allowing any matching of non-variables
(in the argument position for binary being matched) following binary
matching. That solution is simple and safe, and since this kind of
code seems to be rare in practice, there is no need to pursue any
more compilicated solution.

Reported-by: Viktor Sovietov

1 files changed, 46 insertions, 2 deletions

diff --git a/lib/compiler/test/bs_match_SUITE.erl b/lib/compiler/test/bs_match_SUITE.erl
index d63d2235d7..e8a92c509e 100644
--- a/lib/compiler/test/bs_match_SUITE.erl
+++ b/lib/compiler/test/bs_match_SUITE.erl
@@ -33,7 +33,8 @@
 	 matching_meets_construction/1,simon/1,matching_and_andalso/1,
 	 otp_7188/1,otp_7233/1,otp_7240/1,otp_7498/1,
 	 match_string/1,zero_width/1,bad_size/1,haystack/1,
-	 cover_beam_bool/1,matched_out_size/1,follow_fail_branch/1]).
+	 cover_beam_bool/1,matched_out_size/1,follow_fail_branch/1,
+	 no_partition/1]).
 
 -export([coverage_id/1,coverage_external_ignore/2]).
 
@@ -57,7 +58,8 @@ groups() ->
        matching_meets_construction,simon,
        matching_and_andalso,otp_7188,otp_7233,otp_7240,
        otp_7498,match_string,zero_width,bad_size,haystack,
-       cover_beam_bool,matched_out_size,follow_fail_branch]}].
+       cover_beam_bool,matched_out_size,follow_fail_branch,
+       no_partition]}].
 
 
 init_per_suite(Config) ->
@@ -1133,6 +1135,48 @@ ffb_2(<<_,T/bitstring>>, List, A) ->
 	[_|_] -> bit_size(T)
     end.
 
+no_partition(_) ->
+    one = no_partition_1(<<"string">>, a1),
+    {two,<<"string">>} = no_partition_1(<<"string">>, a2),
+    {two,<<>>} = no_partition_1(<<>>, a2),
+    {two,a} = no_partition_1(a, a2),
+    three = no_partition_1(undefined, a3),
+    {four,a,[]} = no_partition_1([a], a4),
+    {five,a,b} = no_partition_1({a,b}, a5),
+
+    one = no_partition_2(<<"string">>, a1),
+    two = no_partition_2(<<"string">>, a2),
+    two = no_partition_2(<<>>, a2),
+    two = no_partition_2(a, a2),
+    three = no_partition_2(undefined, a3),
+    four = no_partition_2(42, a4),
+    five = no_partition_2([], a5),
+    six = no_partition_2(42.0, a6),
+    ok.
+
+no_partition_1(<<"string">>, a1) ->
+    one;
+no_partition_1(V, a2) ->
+    {two,V};
+no_partition_1(undefined, a3) ->
+    three;
+no_partition_1([H|T], a4) ->
+    {four,H,T};
+no_partition_1({A,B}, a5) ->
+    {five,A,B}.
+
+no_partition_2(<<"string">>, a1) ->
+    one;
+no_partition_2(_, a2) ->
+    two;
+no_partition_2(undefined, a3) ->
+    three;
+no_partition_2(42, a4) ->
+    four;
+no_partition_2([], a5) ->
+    five;
+no_partition_2(42.0, a6) ->
+    six.
 
 check(F, R) ->
     R = F().