diff options
| author |  Abseil Team <absl-team@google.com> | 2019-04-24 01:44:22 -0700 |
|---|---|---|
| committer |  Matt Calabrese <calabrese@x.team> | 2019-04-24 14:35:20 -0400 |
| commit | 33841c5c963aa9c3f096ef8e6c1e71624b941940 (patch) | |
| tree | 8ddb90d308e40dfcb793d3db77759741b4e809cf | |
| parent | ca3f87560a0eef716195cadf66dc6b938a579ec6 (diff) | |
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
| -rw-r--r-- | absl/debugging/symbolize_elf.inc | 2 | ||||
| -rw-r--r-- | absl/hash/BUILD.bazel | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/absl/debugging/symbolize_elf.inc b/absl/debugging/symbolize_elf.inc index 05fc2979..5ac7ff5d 100644 --- a/absl/debugging/symbolize_elf.inc +++ b/absl/debugging/symbolize_elf.inc @@ -305,7 +305,7 @@ class Symbolizer { char *tmp_buf, int tmp_buf_size); enum { - SYMBOL_BUF_SIZE = 2048, + SYMBOL_BUF_SIZE = 3072, TMP_BUF_SIZE = 1024, SYMBOL_CACHE_LINES = 128, }; diff --git a/absl/hash/BUILD.bazel b/absl/hash/BUILD.bazel index e1e6eae8..8c2daf70 100644 --- a/absl/hash/BUILD.bazel +++ b/absl/hash/BUILD.bazel @@ -35,10 +35,10 @@ cc_library( copts = ABSL_DEFAULT_COPTS, linkopts = ABSL_DEFAULT_LINKOPTS, deps = [ + ":city", "//absl/base:core_headers", "//absl/base:endian", "//absl/container:fixed_array", - "//absl/hash:city", "//absl/meta:type_traits", "//absl/numeric:int128", "//absl/strings", |