File 0192-Make-0-bsl-BigNumber-consistently-succeed.patch of Package erlang
From 8c0569d2b5c26545cb7abd9063a1abda7ebd13e9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Thu, 10 Aug 2017 11:46:48 +0200
Subject: [PATCH] Make '0 bsl BigNumber' consistently succeed
'0 bsl 134217728' would fail with a system limit exception on a 32-bit
BEAM machine, but not on a 64-bit BEAM machine. Smaller values
on the right would always work.
Make erlang:bsl(0, BigNumber) always return 0 to make for consistency.
(The previous commit accidentally did that change for
'0 bsl BigNumber'.)
---
erts/emulator/beam/erl_arith.c | 6 +++++-
erts/emulator/test/big_SUITE.erl | 7 +++++++
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/erts/emulator/beam/erl_arith.c b/erts/emulator/beam/erl_arith.c
index 861532f24..f2a3e411e 100644
--- a/erts/emulator/beam/erl_arith.c
+++ b/erts/emulator/beam/erl_arith.c
@@ -276,8 +276,12 @@ shift(Process* p, Eterm arg1, Eterm arg2, int right)
goto do_bsl;
} else if (is_small(arg1) || is_big(arg1)) {
/*
- * N bsl PositiveBigNum is too large to represent.
+ * N bsl PositiveBigNum is too large to represent,
+ * unless N is 0.
*/
+ if (arg1 == make_small(0)) {
+ BIF_RET(arg1);
+ }
BIF_ERROR(p, SYSTEM_LIMIT);
}
/* Fall through if the left argument is not an integer. */
diff --git a/erts/emulator/test/big_SUITE.erl b/erts/emulator/test/big_SUITE.erl
index c30876021..5939d024a 100644
--- a/erts/emulator/test/big_SUITE.erl
+++ b/erts/emulator/test/big_SUITE.erl
@@ -339,6 +339,13 @@ system_limit(Config) when is_list(Config) ->
{'EXIT',{system_limit,_}} = (catch apply(erlang, id('bsl'), [Maxbig,2])),
{'EXIT',{system_limit,_}} = (catch id(1) bsl (1 bsl 45)),
{'EXIT',{system_limit,_}} = (catch id(1) bsl (1 bsl 69)),
+
+ %% There should be no system_limit exception when shifting a zero.
+ 0 = id(0) bsl (1 bsl 128),
+ 0 = id(0) bsr -(1 bsl 128),
+ Erlang = id(erlang),
+ 0 = Erlang:'bsl'(id(0), 1 bsl 128),
+ 0 = Erlang:'bsr'(id(0), -(1 bsl 128)),
ok.
maxbig() ->
--
2.14.1
