Remove explicit padding from CacheAlignedInstrumentedMutex #9809
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Fixes facebook#9779. The padding at the end of a struct is added implicitly according to the sizeof spec: "When applied to a class, the result is the number of bytes in an object of that class including any padding required for placing objects of that type in an array" (https://eel.is/c++draft/expr.sizeof#2.sentence-2). We should drop the explicit padding since it assumed support for zero-length arrays, which is non-standard. Test Plan: rely on CI
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riversand963
approved these changes
Apr 5, 2022
| }; | ||
| static_assert(sizeof(CacheAlignedInstrumentedMutex) % CACHE_LINE_SIZE == 0); | ||
| static_assert(alignof(CacheAlignedInstrumentedMutex) != CACHE_LINE_SIZE || |
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Should line 56 be removed as well?
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Reverted because it caused an error:
/home/circleci/project/db/db_impl/db_impl.cc: In constructor ‘rocksdb::DBImpl::DBImpl(const rocksdb::DBOptions&, const string&, bool, bool, bool)’:
/home/circleci/project/db/db_impl/db_impl.cc:239:62: error: no matching function for call to ‘rocksdb::CacheAlignedInstrumentedMutex::CacheAlignedInstrumentedMutex(rocksdb::Statistics*&, rocksdb::SystemClock* const&, rocksdb::Tickers, const bool&)’
239 | immutable_db_options_.listeners, dbname_) {
...
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This reverts commit ff37903.
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Summary: Fixes #9779. The padding at the end of a struct is added implicitly according to the sizeof spec: "When applied to a class, the result is the number of bytes in an object of that class including any padding required for placing objects of that type in an array" (https://eel.is/c++draft/expr.sizeof#2.sentence-2). We should drop the explicit padding since it assumed support for zero-length arrays, which is non-standard. Pull Request resolved: #9809 Test Plan: rely on CI Reviewed By: riversand963 Differential Revision: D35413496 Pulled By: ajkr fbshipit-source-id: 25d52ca45e648ad0d5657149f26f6adecbed1cb4
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Fixes #9779.
The padding at the end of a struct is added implicitly according to the
sizeof spec: "When applied to a class, the result is the
number of bytes in an object of that class including any padding
required for placing objects of that type in an array"
(https://eel.is/c++draft/expr.sizeof#2.sentence-2). We should drop the
explicit padding since it assumed support for zero-length arrays, which
is non-standard.
Test Plan: rely on CI