How to enable RTTI without modify leveldb/CMakeList.txt

[luguoxiang]

I use cmake to build leveldb with my project,

add_subdirectory(leveldb)
target_link_libraries( ${APP_EXEC}  ...leveldb )

It seems leveldb disable RTTI (-f no-rtti) by default, there is some other third party library in my project which requires RTTI, is there any way to enable RTTI without modify leveldb/CMakeList.txt?

[cmumford]

Does your other third party library need to dynamically determine the type of the leveldb objects in include/leveldb, or for other objects? If not the you should be OK to leave RTTI disabled for leveldb, but enable it for other code. However, if you really do need RTTI enabled for leveldb then I think you will need to modify CMakeLists.txt as it is hard-coded to be disabled. I'm not a CMake expert, so there may be some environment variable that can modify CMAKE_CXX_FLAGS.

[luguoxiang]

It seems leveldb::Comparator does not work when RTTI disabled for leveldb and mycode is rtti enabled: https://stackoverflow.com/questions/57670944/undefined-symbols-for-architecture-x86-64-typeinfo-for-leveldbcomparator, is there any way to fix this issue while leaving my code rtti enabled?

[muffinrecon]

@luguoxiang

Separating the comparator into its own cpp file and compiling with the -fno-rtti flag worked best for me.

[vermorth]

@luguoxiang
I have the same problem as you. And my code uses a lot of typeid, so I can't do as @muffinrecon said:

Separating the comparator into its own cpp file and compiling with the -fno-rtti flag worked best for me.

My only way is to enable rtti for leveldb. What did you do in the end?

[luguoxiang]

I went back to use leveled 1.22 which seems enabled rtti by default.

[susnux]

This breaks @ceph /ceph:

[ 1547s] /usr/lib64/gcc/x86_64-suse-linux/10/../../../../x86_64-suse-linux/bin/ld: ../../lib/libkv.a(LevelDBStore.cc.o):(.data.rel.ro._ZTI17CephLevelDBLogger[_ZTI17CephLevelDBLogger]+0x10): undefined reference to `typeinfo for leveldb::Logger'

[kalebskeithley]

The addition of -fno-rtti between 1.22 and 1.23 is an ABI change and should include an soname bump as well.

As susnux mentions above, this breaks the Ceph build, in my case in Fedora F35/rawhide.

see #927

[wbolster]

this also prevents leveldb 1.23 to be used in python via plyvel, see e.g. wbolster/plyvel#114