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File 0229-stdlib-Correct-evaluation-order-when-creating-bitstr.patch of Package erlang (Revision 1e94e72e3f4fed1ca9cd5c2fd777ed02)

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From a6bd8264bf7594dc6711396cdbccef67a0e94e40 Mon Sep 17 00:00:00 2001
From: Hans Bolinder <hasse@erlang.org>
Date: Mon, 12 Oct 2020 13:21:30 +0200
Subject: [PATCH 2/2] stdlib: Correct evaluation order when creating bitstrings

The evaluation of bitstring creation separates the evaluation of
values and sizes from the creation of binaries in order to get the
same error messages as output by the compiler. It could even happen
that compiled code got stuck in a loop while interpreted code failed.
---
 lib/stdlib/src/eval_bits.erl       | 53 +++++++++++++++++++-----------
 lib/stdlib/test/erl_eval_SUITE.erl |  6 +++-
 2 files changed, 39 insertions(+), 20 deletions(-)

diff --git a/lib/stdlib/src/eval_bits.erl b/lib/stdlib/src/eval_bits.erl
index 157d823a09..35eca359dc 100644
--- a/lib/stdlib/src/eval_bits.erl
+++ b/lib/stdlib/src/eval_bits.erl
@@ -64,39 +64,54 @@ convert_list(List) ->
 expr_grp(Fields, Bindings, EvalFun) ->
     expr_grp(Fields, Bindings, EvalFun, <<>>).
 
-expr_grp([Field | FS], Bs0, Lf, Acc) ->
-    {Bin,Bs} = eval_field(Field, Bs0, Lf),
-    expr_grp(FS, Bs, Lf, <<Acc/binary-unit:1,Bin/binary-unit:1>>);
-expr_grp([], Bs0, _Lf, Acc) ->
-    {value,Acc,Bs0}.
+expr_grp(FS, Bs0, Ef, Acc) ->
+    %% Separate the evaluation of values, sizes, and TLS:s from the
+    %% creation of the binary in order to mimic compiled code when it
+    %% comes to loops and failures.
+    {ListOfEvalField,Bs1} = expr_grp1(FS, Bs0, Ef, []),
+    {value,create_binary(ListOfEvalField, Acc),Bs1}.
+
+expr_grp1([Field | FS], Bs0, Ef, ListOfEvalField) ->
+    {EvalField,Bs} = eval_field(Field, Bs0, Ef),
+    expr_grp1(FS, Bs, Ef, [EvalField|ListOfEvalField]);
+expr_grp1([], Bs, _Ef, ListOfFieldData) ->
+    {lists:reverse(ListOfFieldData),Bs}.
+
+create_binary([EvalField|ListOfEvalField], Acc) ->
+    Bin = EvalField(),
+    create_binary(ListOfEvalField, <<Acc/binary-unit:1,Bin/binary-unit:1>>);
+create_binary([], Acc) ->
+    Acc.
 
 eval_field({bin_element, _, {string, _, S}, {integer,_,8}, [integer,{unit,1},unsigned,big]}, Bs0, _Fun) ->
     Latin1 = [C band 16#FF || C <- S],
-    {list_to_binary(Latin1),Bs0};
+    {fun() -> list_to_binary(Latin1) end,Bs0};
 eval_field({bin_element, _, {string, _, S}, default, default}, Bs0, _Fun) ->
     Latin1 = [C band 16#FF || C <- S],
-    {list_to_binary(Latin1),Bs0};
+    {fun() ->list_to_binary(Latin1) end,Bs0};
 eval_field({bin_element, Line, {string, _, S}, Size0, Options0}, Bs0, Fun) ->
     {Size1,[Type,{unit,Unit},Sign,Endian]} =
         make_bit_type(Line, Size0, Options0),
     {value,Size,Bs1} = Fun(Size1, Bs0),
-    Res = << <<(eval_exp_field1(C, Size, Unit,
-				Type, Endian, Sign))/bitstring>> ||
-	      C <- S >>,
-    case S of
-        "" -> % find errors also when the string is empty
-            _ = eval_exp_field1(0, Size, Unit, Type, Endian, Sign),
-            ok;
-        _ ->
-            ok
-    end,
-    {Res,Bs1};
+    {fun() ->
+             Res = << <<(eval_exp_field1(C, Size, Unit,
+                                         Type, Endian, Sign))/bitstring>> ||
+                       C <- S >>,
+             case S of
+                 "" -> % find errors also when the string is empty
+                     _ = eval_exp_field1(0, Size, Unit, Type, Endian, Sign),
+                     ok;
+                 _ ->
+                     ok
+             end,
+             Res
+     end,Bs1};
 eval_field({bin_element,Line,E,Size0,Options0}, Bs0, Fun) ->
     {value,V,Bs1} = Fun(E, Bs0),
     {Size1,[Type,{unit,Unit},Sign,Endian]} = 
         make_bit_type(Line, Size0, Options0),
     {value,Size,Bs} = Fun(Size1, Bs1),
-    {eval_exp_field1(V, Size, Unit, Type, Endian, Sign),Bs}.
+    {fun() -> eval_exp_field1(V, Size, Unit, Type, Endian, Sign) end,Bs}.
 
 eval_exp_field1(V, Size, Unit, Type, Endian, Sign) ->
     try
diff --git a/lib/stdlib/test/erl_eval_SUITE.erl b/lib/stdlib/test/erl_eval_SUITE.erl
index 392e52bdb1..e6754d13f5 100644
--- a/lib/stdlib/test/erl_eval_SUITE.erl
+++ b/lib/stdlib/test/erl_eval_SUITE.erl
@@ -1146,7 +1146,7 @@ otp_14826(_Config) ->
     backtrace_check("<<100:8/foo>>.",
                     {undefined_bittype,foo},
                     [{eval_bits,make_bit_type,3},eval_bits,
-                     eval_bits,erl_eval],
+                     eval_bits,eval_bits],
                     none, none),
     backtrace_check("B = <<\"foo\">>, <<B/binary-unit:7>>.",
                     badarg,
@@ -1750,6 +1750,10 @@ otp_16865(Config) when is_list(Config) ->
     check(fun() -> << <<>> || <<34:(1/0)>> <= <<"string">> >> end,
           "<< <<>> || <<34:(1/0)>> <= <<\"string\">> >>.",
           <<>>),
+    %% The order of evaluation is important. Follow the example set by
+    %% compiled code:
+    error_check("<< <<>> || <<>> <= <<1:(-1), (fun() -> a = b end())>> >>.",
+                {badmatch, b}),
     ok.
 
 %% Check the string in different contexts: as is; in fun; from compiled code.
-- 
2.26.2

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