e24734f843
Summary: After https://github.com/facebook/rocksdb/issues/9515 added a unique_ptr to Status, we see some warnings-as-error in some internal builds like this: ``` stderr: rocksdb/src/db/compaction/compaction_job.cc:2839:7: error: offset of on non-standard-layout type 'struct CompactionServiceResult' [-Werror,-Winvalid-offsetof] {offsetof(struct CompactionServiceResult, status), ^ ~~~~~~ ``` I see three potential solutions to resolving this: * Expand our use of an idiom that works around the warning (see offset_of functions removed in this change, inspired by https://gist.github.com/graphitemaster/494f21190bb2c63c5516) However, this construction is invoking undefined behavior that assumes consistent layout with no compiler-introduced indirection. A compiler incompatible with our assumptions will likely compile the code and exhibit undefined behavior. * Migrate to something in place of offset, like a function mapping CompactionServiceResult* to Status* (for the `status` field). This might be required in the long term. * **Selected:** Use our new C++17 dependency to use offsetof in a well-defined way when the compiler allows it. From a comment on https://gist.github.com/graphitemaster/494f21190bb2c63c5516: > A final note: in C++17, offsetof is conditionally supported, which > means that you can use it on any type (not just standard layout > types) and the compiler will error if it can't compile it correctly. > That appears to be the best option if you can live with C++17 and > don't need constexpr support. The C++17 semantics are confirmed on https://en.cppreference.com/w/cpp/types/offsetof, so we can suppress the warning as long as we accept that we might run into a compiler that rejects the code, and at that point we will find a solution, such as the more intrusive "migrate" solution above. Although this is currently only showing in our buck build, it will surely show up also with make and cmake, so I have updated those configurations as well. Also in the buck build, -Wno-expansion-to-defined does not appear to be needed anymore (both current compiler configurations) so I removed it. Pull Request resolved: https://github.com/facebook/rocksdb/pull/9563 Test Plan: Tried out buck builds with both current compiler configurations Reviewed By: riversand963 Differential Revision: D34220931 Pulled By: pdillinger fbshipit-source-id: d39436008259bd1eaaa87c77be69fb2a5b559e1f |
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RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key-value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it especially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/main/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Questions and discussions are welcome on the RocksDB Developers Public Facebook group and email list on Google Groups.
License
RocksDB is dual-licensed under both the GPLv2 (found in the COPYING file in the root directory) and Apache 2.0 License (found in the LICENSE.Apache file in the root directory). You may select, at your option, one of the above-listed licenses.