tvl-depot/absl/hash/BUILD.bazel
Abseil Team 33841c5c96 Export of internal Abseil changes.
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bb92c768e2271ddbebc1b1eb7e16a7b7c86a6e1c by Abseil Team <absl-team@google.com>:

Automated g4 rollback of changelist 244998488.

*** Reason for rollback ***

I'm seeing test failures, rolling this back.

*** Original change description ***

BEGIN_PUBLIC

The default constructor for optional<T> is filling dummy_ with zeros (see https://godbolt.org/z/IVea7X for a reduced example), which has a performance impact for large Ts. This comes from the gcc6 bugfix that made dummy as big as T. Because constexpr constructors are required to initialize all members of a struct, we cannot prevent this in a standard-compliant way as soon as dummy has any members (note that clang will happily accept adding a `constexpr dummy_type() {}` constructor...

***

PiperOrigin-RevId: 245004716

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6e3ee35af50ffbee604c22300f3260ebc5f6cf52 by Abseil Team <absl-team@google.com>:

The default constructor for optional<T> is filling dummy_ with zeros (see https://godbolt.org/z/IVea7X for a reduced example), which has a performance impact for large Ts. This comes from the gcc6 bugfix that made dummy as big as T. Because constexpr constructors are required to initialize all members of a struct, we cannot prevent this in a standard-compliant way as soon as dummy has any members (note that clang will happily accept adding a `constexpr dummy_type() {}` constructor to dummy_type to prevent zero-initialization, but this is UB AFAICT).

This all stems from the fact that we're constructing an object by using placement new on dummy_. The solution I'm using here is to do the placement new on the actual data_. This creates a new issue in when T is volatile, because we can no longer use `&data_` to do the placement new. The solution I'm using here is to make data_ a non-const and non-volatile T, and only provide fully possibly qualified access through `reference()` accessors. I think this correctly prevents UB.

PiperOrigin-RevId: 244998488

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4f52e64c4cf6aef8df6360007bcc53d8b00db2b4 by Abseil Team <absl-team@google.com>:

Increase SYMBOL_BUF_SIZE from 2KB to 3KB.

PiperOrigin-RevId: 244954529
GitOrigin-RevId: bb92c768e2271ddbebc1b1eb7e16a7b7c86a6e1c
Change-Id: Iaed9a027064a9ecd194c5c146169c683b77f12ef
2019-04-24 14:35:20 -04:00

120 lines
2.8 KiB
Text

#
# Copyright 2018 The Abseil Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
load(
"//absl:copts/configure_copts.bzl",
"ABSL_DEFAULT_COPTS",
"ABSL_DEFAULT_LINKOPTS",
"ABSL_TEST_COPTS",
)
package(default_visibility = ["//visibility:public"])
licenses(["notice"]) # Apache 2.0
cc_library(
name = "hash",
srcs = [
"internal/hash.cc",
"internal/hash.h",
],
hdrs = ["hash.h"],
copts = ABSL_DEFAULT_COPTS,
linkopts = ABSL_DEFAULT_LINKOPTS,
deps = [
":city",
"//absl/base:core_headers",
"//absl/base:endian",
"//absl/container:fixed_array",
"//absl/meta:type_traits",
"//absl/numeric:int128",
"//absl/strings",
"//absl/types:optional",
"//absl/types:variant",
"//absl/utility",
],
)
cc_library(
name = "hash_testing",
testonly = 1,
hdrs = ["hash_testing.h"],
linkopts = ABSL_DEFAULT_LINKOPTS,
deps = [
":spy_hash_state",
"//absl/meta:type_traits",
"//absl/strings",
"//absl/types:variant",
"@com_google_googletest//:gtest",
],
)
cc_test(
name = "hash_test",
srcs = ["hash_test.cc"],
copts = ABSL_TEST_COPTS,
linkopts = ABSL_DEFAULT_LINKOPTS,
deps = [
":hash",
":hash_testing",
"//absl/base:core_headers",
"//absl/container:flat_hash_set",
"//absl/hash:spy_hash_state",
"//absl/meta:type_traits",
"//absl/numeric:int128",
"@com_google_googletest//:gtest_main",
],
)
cc_library(
name = "spy_hash_state",
testonly = 1,
hdrs = ["internal/spy_hash_state.h"],
copts = ABSL_DEFAULT_COPTS,
linkopts = ABSL_DEFAULT_LINKOPTS,
visibility = ["//visibility:private"],
deps = [
":hash",
"//absl/strings",
"//absl/strings:str_format",
],
)
cc_library(
name = "city",
srcs = ["internal/city.cc"],
hdrs = [
"internal/city.h",
],
copts = ABSL_DEFAULT_COPTS,
linkopts = ABSL_DEFAULT_LINKOPTS,
deps = [
"//absl/base:config",
"//absl/base:core_headers",
"//absl/base:endian",
],
)
cc_test(
name = "city_test",
srcs = ["internal/city_test.cc"],
copts = ABSL_TEST_COPTS,
linkopts = ABSL_DEFAULT_LINKOPTS,
deps = [
":city",
"@com_google_googletest//:gtest_main",
],
)