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| author | Björn-Egil Dahlberg <[email protected]> | 2015-04-01 15:30:12 +0200 |
|---|---|---|
| committer | Björn-Egil Dahlberg <[email protected]> | 2015-04-10 15:50:36 +0200 |
| commit | 2a0ff8b50a68d51e44fddf36867f390b64a4f2bf (patch) | |
| tree | d9d090305c992874320ca19dcf9381259e0b8088 /erts/emulator/test | |
| parent | cc722af4d62d749d2a75155e91a2a1562aeb2a5a (diff) | |
| download | otp-2a0ff8b50a68d51e44fddf36867f390b64a4f2bf.tar.gz otp-2a0ff8b50a68d51e44fddf36867f390b64a4f2bf.tar.bz2 otp-2a0ff8b50a68d51e44fddf36867f390b64a4f2bf.zip | |
erts: Ensure hashing of zero is consistent
Erlang treats positive and negative zero as equal, meaning,
true = 0.0 =:= 0.0/-1
However, Erlangs hash functions: hash, phash and phash2 did not
reflect this behaviour. Meaning, the hash values produced by
the different hash functions would not be identical for positive
and negative zero.
This commit ensures that hash value of positive zero is always
produced regardless of the signedness of the zero float, i.e.
true = erlang:phash2(0.0) =:= erlang:phash2(0.0/-1)
Diffstat (limited to 'erts/emulator/test')
| -rw-r--r-- | erts/emulator/test/hash_SUITE.erl | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/erts/emulator/test/hash_SUITE.erl b/erts/emulator/test/hash_SUITE.erl index 647bb45049..5fa45f772d 100644 --- a/erts/emulator/test/hash_SUITE.erl +++ b/erts/emulator/test/hash_SUITE.erl @@ -73,6 +73,7 @@ config(priv_dir,_) -> init_per_group/2,end_per_group/2, test_basic/1,test_cmp/1,test_range/1,test_spread/1, test_phash2/1,otp_5292/1,bit_level_binaries/1,otp_7127/1, + test_hash_zero/1, end_per_testcase/2,init_per_testcase/2]). init_per_testcase(_Case, Config) -> Dog=test_server:timetrap(test_server:minutes(10)), @@ -86,7 +87,9 @@ suite() -> [{ct_hooks,[ts_install_cth]}]. all() -> [test_basic, test_cmp, test_range, test_spread, - test_phash2, otp_5292, bit_level_binaries, otp_7127]. + test_phash2, otp_5292, bit_level_binaries, otp_7127, + test_hash_zero + ]. groups() -> []. @@ -160,6 +163,8 @@ otp_7127(doc) -> otp_7127(Config) when is_list(Config) -> otp_7127_test(). +test_hash_zero(Config) when is_list(Config) -> + hash_zero_test(). -endif. @@ -591,6 +596,26 @@ otp_7127_test() -> 38990304 = erlang:phash2(<<"Scott9">>), ok. +hash_zero_test() -> + Zs = [0.0, -0.0, 0/-1, 0.0/-1, 0/-(1 bsl 65), + binary_to_term(<<131,70,0,0,0,0,0,0,0,0>>), %% +0.0 + binary_to_term(<<131,70,128,0,0,0,0,0,0,0>>)], %% -0.0 + ok = hash_zero_test(Zs,fun(T) -> erlang:phash2(T, 1 bsl 32) end), + ok = hash_zero_test(Zs,fun(T) -> erlang:phash(T, 1 bsl 32) end), + ok = hash_zero_test(Zs,fun(T) -> erlang:hash(T, (1 bsl 27) - 1) end), + ok. + +hash_zero_test([Z|Zs],F) -> + hash_zero_test(Zs,Z,F(Z),F). +hash_zero_test([Z|Zs],Z0,V,F) -> + true = Z0 =:= Z, %% assert exact equal + Z0 = Z, %% assert matching + V = F(Z), %% assert hash + hash_zero_test(Zs,Z0,V,F); +hash_zero_test([],_,_,_) -> + ok. + + %% %% Reference implementation of integer hashing %% |