mirror of
https://github.com/facebook/rocksdb.git
synced 2024-11-28 15:33:54 +00:00
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 |
||
|---|---|---|
| .. | ||
| buckify_rocksdb.py | ||
| check_buck_targets.sh | ||
| rocks_test_runner.sh | ||
| targets_builder.py | ||
| targets_cfg.py | ||
| util.py | ||