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authorSverker Eriksson <[email protected]>2018-12-17 16:03:36 +0100
committerSverker Eriksson <[email protected]>2018-12-17 16:47:41 +0100
commitc8d3bff46adbff3205eaf76de8a634557cbd4af4 (patch)
tree561b2ff0e426ca7d4b1687e9f8090f33634db429 /erts/emulator
parentabc4fd372d476821448dfb949bea4e28ab82ac26 (diff)
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erts: Fix bug in 'band' of two negative numbers, one big
Similar bug as for bxor fixed by abc4fd372d476821448dfb9 Ex: 1> io:format("~.16B\n", [-16#1110000000000000000 band (-1)]). -1120000000000000000 Wrong result for (-X bsl WS) band -Y. where X is any positive integer WS is erlang:system_info(wordsize)*8*N where N is 1 or larger Y is any positive integer smaller than (1 bsl WS) Fix: The subtraction of 1 (for 2-complement conversion) must be carried along all the way to the last words.
Diffstat (limited to 'erts/emulator')
-rw-r--r--erts/emulator/beam/big.c7
-rw-r--r--erts/emulator/test/big_SUITE.erl39
2 files changed, 42 insertions, 4 deletions
diff --git a/erts/emulator/beam/big.c b/erts/emulator/beam/big.c
index 323cd6c518..6497089419 100644
--- a/erts/emulator/beam/big.c
+++ b/erts/emulator/beam/big.c
@@ -1139,8 +1139,11 @@ static dsize_t I_band(ErtsDigit* x, dsize_t xl, short xsgn,
*r++ = ~c1 & ~c2;
x++; y++;
}
- while(xl--)
- *r++ = ~*x++;
+ while(xl--) {
+ DSUBb(*x,0,b1,c1);
+ *r++ = ~c1;
+ x++;
+ }
}
}
return I_btrail(r0, r, sign);
diff --git a/erts/emulator/test/big_SUITE.erl b/erts/emulator/test/big_SUITE.erl
index c5bb228bc3..4b11c4905f 100644
--- a/erts/emulator/test/big_SUITE.erl
+++ b/erts/emulator/test/big_SUITE.erl
@@ -23,7 +23,7 @@
init_per_group/2,end_per_group/2]).
-export([t_div/1, eq_28/1, eq_32/1, eq_big/1, eq_math/1, big_literals/1,
borders/1, negative/1, big_float_1/1, big_float_2/1,
- bxor_2pow/1,
+ bxor_2pow/1, band_2pow/1,
shift_limit_1/1, powmod/1, system_limit/1, toobig/1, otp_6692/1]).
%% Internal exports.
@@ -41,7 +41,7 @@ suite() -> [{ct_hooks,[ts_install_cth]}].
all() ->
[t_div, eq_28, eq_32, eq_big, eq_math, big_literals,
borders, negative, {group, big_float}, shift_limit_1,
- bxor_2pow,
+ bxor_2pow, band_2pow,
powmod, system_limit, toobig, otp_6692].
groups() ->
@@ -476,3 +476,38 @@ my_bxor(A, B, N, Acc0) ->
false -> Acc0 bor (1 bsl N)
end,
my_bxor(A bsr 1, B bsr 1, N+1, Acc1).
+
+
+%% ERL-804
+band_2pow(_Config) ->
+ IL = lists:seq(8*3, 8*16, 4),
+ JL = lists:seq(0, 64),
+ [band_2pow_1((1 bsl I), (1 bsl J))
+ || I <- IL, J <- JL],
+ ok.
+
+band_2pow_1(A, B) ->
+ for(-1,1, fun(Ad) ->
+ for(-1,1, fun(Bd) ->
+ band_2pow_2(A+Ad, B+Bd),
+ band_2pow_2(-A+Ad, B+Bd),
+ band_2pow_2(A+Ad, -B+Bd),
+ band_2pow_2(-A+Ad, -B+Bd)
+ end)
+ end).
+
+band_2pow_2(A, B) ->
+ Correct = my_band(A, B),
+ case A band B of
+ Correct -> ok;
+ Wrong ->
+ io:format("~.16# band ~.16#\n", [A,B]),
+ io:format("Expected ~.16#\n", [Correct]),
+ io:format("Got ~.16#\n", [Wrong]),
+ ct:fail({failed, 'band'})
+
+ end.
+
+%% Implement band without band
+my_band(A, B) ->
+ bnot ((bnot A) bor (bnot B)).