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File 0938-beam_call_types-Correct-optimization-of-setelement-3.patch of Package erlang (Revision b4f72044e1af8cfe32130ab849a401a1)

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From dfc5d7dfbf3fa0e0333d325e01f064be08b35c68 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Fri, 25 Mar 2022 08:46:38 +0100
Subject: [PATCH] beam_call_types: Correct optimization of setelement/3

2ea04617d18bc3 introduced a bug in the handling of calls to
`setelement/3`. Consider this module:

-module(bug).
    -export([bug/0]).

bug() ->
        set(2, {a,b}),
        set(3, {a,b}).

set(Pos, Tuple) ->
        setelement(Pos, Tuple, something).

The second call to `set/2` will fail because the position is `3` is
beyond the end of the tuple. Because of that failed call, the compiler
would incorrectly assume that the call to `setelement/3` in `set/2`
would always fail, and there would be a very confusing exception:

1> bug:bug().
    ** exception error: no true branch found when evaluating an if expression
         in function  bug:set/2 (bug.erl, line 8)

This commit fixes the bug. With this bug fix, the exception will look
like:

4> bug:bug().
    ** exception error: bad argument
         in function  setelement/3
            called as setelement(3,{a,b},something)
            *** argument 1: out of range
         in call from bug:set/2 (bug.erl, line 9)
---
 lib/compiler/src/beam_call_types.erl  | 13 +++++++++----
 lib/compiler/test/beam_type_SUITE.erl | 17 +++++++++++++++++
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/lib/compiler/test/beam_type_SUITE.erl b/lib/compiler/test/beam_type_SUITE.erl
index fcd2c1c915..ca072a89e5 100644
--- a/lib/compiler/test/beam_type_SUITE.erl
+++ b/lib/compiler/test/beam_type_SUITE.erl
@@ -396,6 +396,15 @@ tuple(_Config) ->
     [] = [X || X <- [], #bird{b = b} == {bird,X}],
     [] = [X || X <- [], 3 == X#bird.a],
 
+    Counters0 = id({0,0,0}),                    %Inexact size.
+    {1,0,0} = Counters1 = increment_element(1, Counters0),
+    {1,1,0} = increment_element(2, Counters1),
+
+    Counters10 = {id(0),id(0),id(0)},           %Exact size.
+    {0,-1,0} = decrement_element(2, Counters10),
+    {0,0,-1} = decrement_element(3, Counters10),
+    {'EXIT',{badarg,_}} = catch decrement_element(4, Counters10),
+
     ok.
 
 do_tuple() ->
@@ -407,6 +416,14 @@ do_literal_tuple_1(X) ->
 do_tuple() ->
     {0, _} = {necessary}.
 
+increment_element(Pos, Cs) ->
+    Ns = element(Pos, Cs),
+    setelement(Pos, Cs, Ns + 1).
+
+decrement_element(Pos, Cs) ->
+    Ns = element(Pos, Cs),
+    setelement(Pos, Cs, Ns - 1).
+
 -record(x, {a}).
 
 record_float(_Config) ->
-- 
2.34.1

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File 0938-beam_call_types-Correct-optimization-of-setelement-3.patch of Package erlang (Revision b4f72044e1af8cfe32130ab849a401a1)

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