CMake warning introduced by libpg_query build changes in #961

[tcm-marcel]

Changing the build system to build libpg_query using Cmake instead of the old Makefile (#961) introduces following CMake warning:

CMake Warning (dev) in src/CMakeLists.txt:
  Policy CMP0022 is not set: INTERFACE_LINK_LIBRARIES defines the link
  interface.  Run "cmake --help-policy CMP0022" for policy details.  Use the
  cmake_policy command to set the policy and suppress this warning.
  Target "peloton" has an INTERFACE_LINK_LIBRARIES property which differs
  from its LINK_INTERFACE_LIBRARIES_DEBUG properties.
  INTERFACE_LINK_LIBRARIES:
    peloton-proto;/usr/lib/x86_64-linux-gnu/libboost_system.so;/usr/lib/x86_64-linux-gnu/libboost_filesystem.so;/usr/lib/x86_64-linux-gnu/libboost_thread.so;/usr/lib/x86_64-linux-gnu/libboost_chrono.so;/usr/lib/x86_64-linux-gnu/libboost_date_time.so;/usr/lib/x86_64-linux-gnu/libboost_atomic.so;/usr/lib/x86_64-linux-gnu/libpthread.so;-lpthread;/usr/lib/x86_64-linux-gnu/libgflags.so;/home/travis/build/tcm-marcel/peloton/build/external/capnp-install/lib/libcapnp-rpc.a;/home/travis/build/tcm-marcel/peloton/build/external/capnp-install/lib/libcapnp.a;/home/travis/build/tcm-marcel/peloton/build/external/capnp-install/lib/libkj-async.a;/home/travis/build/tcm-marcel/peloton/build/external/capnp-install/lib/libkj.a;-lpthread;$<$<NOT:$<CONFIG:DEBUG>>:/usr/lib/x86_64-linux-gnu/libprotobuf.so>;$<$<CONFIG:DEBUG>:/usr/lib/x86_64-linux-gnu/libprotobuf.so>;-lpthread;/usr/lib/x86_64-linux-gnu/libevent.so;/usr/lib/x86_64-linux-gnu/libevent_pthreads.so;/usr/lib/x86_64-linux-gnu/libpqxx.so;/usr/lib/x86_64-linux-gnu/libpq.so;-lssl;LLVMCore;LLVMMCJIT;LLVMX86CodeGen;LLVMX86Desc;LLVMX86Info;LLVMX86CodeGen;LLVMX86AsmPrinter;LLVMX86AsmParser;LLVMX86Desc;LLVMX86Info;LLVMX86Disassembler;peloton-proto;pg_query
  LINK_INTERFACE_LIBRARIES_DEBUG:
    peloton-proto;/usr/lib/x86_64-linux-gnu/libboost_system.so;/usr/lib/x86_64-linux-gnu/libboost_filesystem.so;/usr/lib/x86_64-linux-gnu/libboost_thread.so;/usr/lib/x86_64-linux-gnu/libboost_chrono.so;/usr/lib/x86_64-linux-gnu/libboost_date_time.so;/usr/lib/x86_64-linux-gnu/libboost_atomic.so;/usr/lib/x86_64-linux-gnu/libpthread.so;-lpthread;/usr/lib/x86_64-linux-gnu/libgflags.so;/home/travis/build/tcm-marcel/peloton/build/external/capnp-install/lib/libcapnp-rpc.a;/home/travis/build/tcm-marcel/peloton/build/external/capnp-install/lib/libcapnp.a;/home/travis/build/tcm-marcel/peloton/build/external/capnp-install/lib/libkj-async.a;/home/travis/build/tcm-marcel/peloton/build/external/capnp-install/lib/libkj.a;-lpthread;/usr/lib/x86_64-linux-gnu/libprotobuf.so;-lpthread;/usr/lib/x86_64-linux-gnu/libevent.so;/usr/lib/x86_64-linux-gnu/libevent_pthreads.so;/usr/lib/x86_64-linux-gnu/libpqxx.so;/usr/lib/x86_64-linux-gnu/libpq.so;-lssl;LLVMCore;LLVMMCJIT;LLVMX86CodeGen;LLVMX86Desc;LLVMX86Info;LLVMX86CodeGen;LLVMX86AsmPrinter;LLVMX86AsmParser;LLVMX86Desc;LLVMX86Info;LLVMX86Disassembler;peloton-proto;pg_query
This warning is for project developers.  Use -Wno-dev to suppress it.

I couldn't find the cause of this warning yet.

• The warning apparently seems to come from libprotobuf and not from the changes to libpg_query, but for some reason it only shows up now.
• INTERFACE_LINK_LIBRARIES contains strings like $<$<NOT:$<CONFIG:DEBUG>> which should have been evaluated before and not show up there at all.

[pmenon]

I'm getting this problem now after syncing.

The problem is related to the "peloton" target, not protobuf. It says so in the warning:

Target "peloton" has an INTERFACE_LINK_LIBRARIES property which differs
  from its LINK_INTERFACE_LIBRARIES_DEBUG properties

[tcm-marcel]

The difference between the two properties is following part:
$<$<NOT:$<CONFIG:DEBUG>>:/usr/lib/x86_64-linux-gnu/libprotobuf.so>;$<$<CONFIG:DEBUG>
vs.
/usr/lib/x86_64-linux-gnu/libprotobuf.so

I don't know where to start looking for the problem. And if I understand cmake correctly, the $<...> part should have been resolved before and not show up in this property at all.