Rocksdb: Build fail with gcc 9

[BusyJay]

Expected behavior

Compilation completes successfully.

Actual behavior

Compilation failure:

$DEBUG_LEVEL is 1
Makefile:168: Warning: Compiling in debug mode. Don't use the resulting binary in production
  GEN      util/build_version.cc
$DEBUG_LEVEL is 1
Makefile:168: Warning: Compiling in debug mode. Don't use the resulting binary in production
  GEN      util/build_version.cc
  CC       cache/clock_cache.o
  CC       cache/lru_cache.o
  CC       cache/sharded_cache.o
  CC       db/builder.o
In file included from ./db/memtable.h:21,
                 from ./db/memtable_list.h:17,
                 from ./db/column_family.h:17,
                 from ./db/version_set.h:31,
                 from ./db/compaction.h:11,
                 from ./db/compaction_iterator.h:13,
                 from db/builder.cc:16:
./db/version_edit.h: In constructor ‘rocksdb::FdWithKeyRange::FdWithKeyRange(rocksdb::FileDescriptor, rocksdb::Slice, rocksdb::Slice, rocksdb::FileMetaData*)’:
./db/version_edit.h:178:33: error: implicitly-declared ‘constexpr rocksdb::FileDescriptor::FileDescriptor(const rocksdb::FileDescriptor&)’ is deprecated [-Werror=deprecated-copy]
  178 |         largest_key(_largest_key) {}
      |                                 ^
./db/version_edit.h:55:19: note: because ‘rocksdb::FileDescriptor’ has user-provided ‘rocksdb::FileDescriptor& rocksdb::FileDescriptor::operator=(const rocksdb::FileDescriptor&)’
   55 |   FileDescriptor& operator=(const FileDescriptor& fd) {
      |                   ^~~~~~~~
./db/version_edit.h: In instantiation of ‘constexpr std::pair<_T1, _T2>::pair(_U1&&, _U2&&) [with _U1 = int&; _U2 = rocksdb::FileMetaData; typename std::enable_if<(std::_PCC<true, _T1, _T2>::_MoveConstructiblePair<_U1, _U2>() && std::_PCC<true, _T1, _T2>::_ImplicitlyMoveConvertiblePair<_U1, _U2>()), bool>::type <anonymous> = true; _T1 = int; _T2 = rocksdb::FileMetaData]’:
/usr/include/c++/9/ext/new_allocator.h:147:4:   required from ‘void __gnu_cxx::new_allocator<_Tp>::construct(_Up*, _Args&& ...) [with _Up = std::pair<int, rocksdb::FileMetaData>; _Args = {int&, rocksdb::FileMetaData}; _Tp = std::pair<int, rocksdb::FileMetaData>]’
/usr/include/c++/9/bits/alloc_traits.h:484:4:   required from ‘static void std::allocator_traits<std::allocator<_CharT> >::construct(std::allocator_traits<std::allocator<_CharT> >::allocator_type&, _Up*, _Args&& ...) [with _Up = std::pair<int, rocksdb::FileMetaData>; _Args = {int&, rocksdb::FileMetaData}; _Tp = std::pair<int, rocksdb::FileMetaData>; std::allocator_traits<std::allocator<_CharT> >::allocator_type = std::allocator<std::pair<int, rocksdb::FileMetaData> >]’
/usr/include/c++/9/bits/vector.tcc:115:30:   required from ‘void std::vector<_Tp, _Alloc>::emplace_back(_Args&& ...) [with _Args = {int&, rocksdb::FileMetaData}; _Tp = std::pair<int, rocksdb::FileMetaData>; _Alloc = std::allocator<std::pair<int, rocksdb::FileMetaData> >]’
./db/version_edit.h:253:48:   required from here
./db/version_edit.h:86:8: error: implicitly-declared ‘constexpr rocksdb::FileDescriptor::FileDescriptor(const rocksdb::FileDescriptor&)’ is deprecated [-Werror=deprecated-copy]
   86 | struct FileMetaData {
      |        ^~~~~~~~~~~~
./db/version_edit.h:55:19: note: because ‘rocksdb::FileDescriptor’ has user-provided ‘rocksdb::FileDescriptor& rocksdb::FileDescriptor::operator=(const rocksdb::FileDescriptor&)’
   55 |   FileDescriptor& operator=(const FileDescriptor& fd) {
      |                   ^~~~~~~~
In file included from /usr/include/c++/9/bits/stl_algobase.h:64,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/string:40,
                 from ./db/builder.h:9,
                 from db/builder.cc:10:
/usr/include/c++/9/bits/stl_pair.h:342:64: note: synthesized method ‘rocksdb::FileMetaData::FileMetaData(rocksdb::FileMetaData&&)’ first required here
  342 |  : first(std::forward<_U1>(__x)), second(std::forward<_U2>(__y)) { }
      |                                                                ^
In file included from ./db/memtable.h:21,
                 from ./db/memtable_list.h:17,
                 from ./db/column_family.h:17,
                 from ./db/version_set.h:31,
                 from ./db/compaction.h:11,
                 from ./db/compaction_iterator.h:13,
                 from db/builder.cc:16:
./db/version_edit.h: In instantiation of ‘constexpr std::pair<_T1, _T2>::pair(_U1&&, const _T2&) [with _U1 = int&; typename std::enable_if<std::_PCC<true, _T1, _T2>::_MoveCopyPair<true, _U1, _T2>(), bool>::type <anonymous> = true; _T1 = int; _T2 = rocksdb::FileMetaData]’:
/usr/include/c++/9/ext/new_allocator.h:147:4:   required from ‘void __gnu_cxx::new_allocator<_Tp>::construct(_Up*, _Args&& ...) [with _Up = std::pair<int, rocksdb::FileMetaData>; _Args = {int&, const rocksdb::FileMetaData&}; _Tp = std::pair<int, rocksdb::FileMetaData>]’
/usr/include/c++/9/bits/alloc_traits.h:484:4:   required from ‘static void std::allocator_traits<std::allocator<_CharT> >::construct(std::allocator_traits<std::allocator<_CharT> >::allocator_type&, _Up*, _Args&& ...) [with _Up = std::pair<int, rocksdb::FileMetaData>; _Args = {int&, const rocksdb::FileMetaData&}; _Tp = std::pair<int, rocksdb::FileMetaData>; std::allocator_traits<std::allocator<_CharT> >::allocator_type = std::allocator<std::pair<int, rocksdb::FileMetaData> >]’
/usr/include/c++/9/bits/vector.tcc:115:30:   required from ‘void std::vector<_Tp, _Alloc>::emplace_back(_Args&& ...) [with _Args = {int&, const rocksdb::FileMetaData&}; _Tp = std::pair<int, rocksdb::FileMetaData>; _Alloc = std::allocator<std::pair<int, rocksdb::FileMetaData> >]’
./db/version_edit.h:258:37:   required from here
./db/version_edit.h:86:8: error: implicitly-declared ‘constexpr rocksdb::FileDescriptor::FileDescriptor(const rocksdb::FileDescriptor&)’ is deprecated [-Werror=deprecated-copy]
   86 | struct FileMetaData {
      |        ^~~~~~~~~~~~
./db/version_edit.h:55:19: note: because ‘rocksdb::FileDescriptor’ has user-provided ‘rocksdb::FileDescriptor& rocksdb::FileDescriptor::operator=(const rocksdb::FileDescriptor&)’
   55 |   FileDescriptor& operator=(const FileDescriptor& fd) {
      |                   ^~~~~~~~
In file included from /usr/include/c++/9/bits/stl_algobase.h:64,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/string:40,
                 from ./db/builder.h:9,
                 from db/builder.cc:10:
/usr/include/c++/9/bits/stl_pair.h:312:51: note: synthesized method ‘rocksdb::FileMetaData::FileMetaData(const rocksdb::FileMetaData&)’ first required here
  312 |        : first(std::forward<_U1>(__x)), second(__y) { }
      |                                                   ^
cc1plus: all warnings being treated as errors
make: *** [Makefile:1953: db/builder.o] Error 1

Steps to reproduce the behavior

% gcc --version                                                                                                                               :(
gcc (GCC) 9.1.1 20190503 (Red Hat 9.1.1-1)
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
% uname -r
5.0.13-300.fc30.x86_64

Simple make command can reproduce the error.

[wanghenshui]

Introduced by gcc 9's new warning checker [-Werror=deprecated-copy]

Here is a fix example:
https://github.com/tsduck/tsduck/issues/205

[BusyJay]

It doesn't compile with clang 8 either unfortunately.

In file included from db/builder.cc:19:
./db/internal_stats.h:112:5: error: declaration shadows a variable in namespace 'rocksdb' [-Werror,-Wshadow]
    WAL_FILE_BYTES,
    ^
./include/rocksdb/statistics.h:196:3: note: previous declaration is here
  WAL_FILE_BYTES,   // Number of bytes written to WAL
  ^
In file included from db/builder.cc:19:
./db/internal_stats.h:113:5: error: declaration shadows a variable in namespace 'rocksdb' [-Werror,-Wshadow]
    WAL_FILE_SYNCED,
    ^

[jprupp]

I managed to build and install RocksDB on my Fedora 30 system with these commands:

CXXFLAGS='-Wno-error=deprecated-copy -Wno-error=pessimizing-move' make shared_lib
sudo make install-shared

I hope that information is useful for anyone else trying.

[biocodz]

The same problem using GCC 9.1 on Ubuntu 18.04 to build rocksdb/master.

The deprecated-copy is thrown because:
Here a copy assignment operator is defined.
Here FileDescriptor fd; is declared.
Each time a copy of FileDescriptor needs to be created e.g.
@175: : fd(_fd), the FileDescriptor copy-constructor is invoked
or
@258: new_files_.emplace_back(level, f); (copy-constructor is automatically called when pushing to vector),
the warning is thrown.
According to C++ docs : The generation of the implicitly-defined copy constructor is deprecated if T has a user-defined destructor or user-defined copy assignment operator. Since C++11
Apparently GCC 8,9 enforce this deprecation.

Explicit copy constructor needs to be implemented, which is also a good practice alongside copy-assignment as follows:

  FileDescriptor(const FileDescriptor& fd) {
    table_reader = fd.table_reader;
    packed_number_and_path_id = fd.packed_number_and_path_id;
    file_size = fd.file_size;
    smallest_seqno = fd.smallest_seqno;
    largest_seqno = fd.largest_seqno;
  }

The pessimizing-move warning is caused by this line.
The call std::move(t) has to be removed i.e. simply return t to allow for the copy elision i.e. to avoid generation of a sub-optimal code.

Using CXXFLAGS is of course only a temporary solution.

After fixing the above errors as described (and the fix works fine), getting the following:

/home/biocodz/rocksdb/db/internal_stats.cc: In member function ‘void rocksdb::InternalStats::DumpCFStatsNoFileHistogram(std::string*)’:
/home/biocodz/rocksdb/db/internal_stats.cc:1384:35: error: implicitly-declared ‘rocksdb::InternalStats::CompactionStats& rocksdb::InternalStats::CompactionStats::operator=(const rocksdb::InternalStats::CompactionStats&)’ is deprecated [-Werror=deprecated-copy]
         1384 |   cf_stats_snapshot_.comp_stats = compaction_stats_sum;
              |                                   ^~~~~~~~~~~~~~~~~~~~
In file included from /home/biocodz/rocksdb/db/internal_stats.cc:11:
/home/biocodz/rocksdb/db/internal_stats.h:220:14: note: because ‘rocksdb::InternalStats::CompactionStats’ has user-provided ‘rocksdb::InternalStats::CompactionStats::CompactionStats(const rocksdb::InternalStats::CompactionStats&)’
          220 |     explicit CompactionStats(const CompactionStats& c)
              |              ^~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
CMakeFiles/rocksdb-shared.dir/build.make:530: recipe for target 'CMakeFiles/rocksdb-shared.dir/db/internal_stats.cc.o' failed

So, now the copy constructor is defined but not the copy assignment => implement.

[biocodz]

Voila, a pull request here

[huitseeker]

@miasantreble should we mark this as fixed by https://github.com/facebook/rocksdb/pull/5553 ?

[cheng-chang]

should be fixed in https://github.com/facebook/rocksdb/pull/6697