From 119e72d3e766089dc7347b75d0530b0c626cff93 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Thu, 9 May 2019 13:22:24 +0200
Subject: Fix compiler crash when funs were matched

Code such as the following would crash the compiler in OTP 22:

   [some_atom = fun some_function/1]

The reason is that the fun would be copied (used both in the match
operation and as a value in the list), and the copy of the fun would
create two wrapper functions with the same name for calling
some_function/1. In OTP 21, the duplicate functions happened not to
cause any harm (one of the wrappers functions would be unused and
ultimately be removed by beam_clean). In OTP 22, the new beam_ssa_type
pass would be confused by the multiple definitions of the wrapper
function.
---
 lib/compiler/src/v3_core.erl    |  3 ++-
 lib/compiler/test/fun_SUITE.erl | 20 ++++++++++++++++++--
 2 files changed, 20 insertions(+), 3 deletions(-)

(limited to 'lib')

diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl
index 3699c9d22e..007a0247f4 100644
--- a/lib/compiler/src/v3_core.erl
+++ b/lib/compiler/src/v3_core.erl
@@ -1811,7 +1811,8 @@ force_safe(Ce, St0) ->
 
 is_safe(#c_cons{}) -> true;
 is_safe(#c_tuple{}) -> true;
-is_safe(#c_var{}) -> true;
+is_safe(#c_var{name={_,_}}) -> false;           %Fun. Not safe.
+is_safe(#c_var{name=_}) -> true;                %Ordinary variable.
 is_safe(#c_literal{}) -> true;
 is_safe(_) -> false.
 
diff --git a/lib/compiler/test/fun_SUITE.erl b/lib/compiler/test/fun_SUITE.erl
index 1df0a05275..7fc6195e31 100644
--- a/lib/compiler/test/fun_SUITE.erl
+++ b/lib/compiler/test/fun_SUITE.erl
@@ -22,7 +22,8 @@
 -export([all/0, suite/0,groups/0,init_per_suite/1, end_per_suite/1, 
 	 init_per_group/2,end_per_group/2,
 	 test1/1,overwritten_fun/1,otp_7202/1,bif_fun/1,
-         external/1,eep37/1,eep37_dup/1,badarity/1,badfun/1]).
+         external/1,eep37/1,eep37_dup/1,badarity/1,badfun/1,
+         duplicated_fun/1]).
 
 %% Internal exports.
 -export([call_me/1,dup1/0,dup2/0]).
@@ -37,7 +38,7 @@ all() ->
 groups() ->
     [{p,[parallel],
       [test1,overwritten_fun,otp_7202,bif_fun,external,eep37,
-       eep37_dup,badarity,badfun]}].
+       eep37_dup,badarity,badfun,duplicated_fun]}].
 
 init_per_suite(Config) ->
     test_lib:recompile(?MODULE),
@@ -261,5 +262,20 @@ badfun(_Config) ->
 expect_badfun(Term, Exit) ->
     {'EXIT',{{badfun,Term},_}} = Exit.
 
+duplicated_fun(_Config) ->
+    try
+        %% The following code used to crash the compiler before
+        %% v3_core:is_safe/1 was corrected to consider fun variables
+        %% unsafe.
+        id([print_result_paths_fun = fun duplicated_fun_helper/1]),
+        ct:error(should_fail)
+    catch
+        error:{badmatch,F} when is_function(F, 1) ->
+            ok
+    end.
+
+duplicated_fun_helper(_) ->
+    ok.
+
 id(I) ->
     I.
-- 
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