[Bug Fix] Fix windows compilation

[talregev]

Fix windows compilation.

[scpeters]

it looks like the windows build still has some issues

[talregev]

it looks like the windows build still has some issues

Yes. Gazebo using c++17 syntax and the 3rdparty is compile with c++11. This is abi issue.

[traversaro]

it looks like the windows build still has some issues

Yes. Gazebo using c++17 syntax and the 3rdparty is compile with c++11. This is abi issue.

Are you sure? The problem seems that (just on Windows) protobuf is now updated to version 23, that has several changes including the public dependency on abseil (see gazebosim/gz-msgs#346 for similar issue). I think changing https://github.com/gazebosim/gazebo-classic/blob/fbb3d12273b02a382085ebf1f1ba72c4da315112/cmake/gazebo-config.cmake.in#LL169C1-L171C56 to:

find_package(Protobuf CONFIG)
if(NOT Protobuf_FOUND)
  find_package(Protobuf REQUIRED)
endif()
if(Protobuf_VERSION VERSION_GREATER_EQUAL 4.0.0)
  list(APPEND @PKG_NAME@_LIBRARIES protobuf::libprotobuf protobuf::libprotoc)
else()
  list(APPEND @PKG_NAME@_INCLUDE_DIRS ${PROTOBUF_INCLUDE_DIRS})
  list(APPEND @PKG_NAME@_LIBRARIES ${PROTOBUF_LIBRARIES})
endif()

may work and reduce the risk of regression for older setups, but I need to do some tests to confirm this.

[talregev]

It my analysis with google search and see similar issues.
I guess the new protobuf using c++17 syntax but the abseil is compile with c++11.

[traversaro]

I guess the new protobuf using c++17 syntax but the abseil is compile with c++11.

No, abseil is compiled with C++17, see conda-forge/conda-forge-pinning-feedstock#4075 (comment) . I guess that you see similar errors in Google searches as the abseil ABI depends on the C++ standard version used in compilation, and hence if there is a mismatch, some abseil symbol can be missing in the actual compiled library, resulting in a "error LNK2019: unresolved external symbol". However, this is not the only reason a linker may not find a symbol: in this case I think that the linker does not find the abseil symbol simply because nobody is linking the abseil shared libraries.

[traversaro]

Note that even if we fix compilation with new protobuf, the Windows build would still fail due to conda-forge/libignition-msgs1-feedstock#30 (that is the reason why there is a failure now only on Windows). So we need to wait also for conda-forge/libignition-msgs1-feedstock#83 to merged, or in the meanwhile we can pin manually libprotobuf to 3.21 .

[talregev]

Note that even if we fix compilation with new protobuf, the Windows build would still fail due to conda-forge/libignition-msgs1-feedstock#30 (that is the reason why there is a failure now only on Windows). So we need to wait also for conda-forge/libignition-msgs1-feedstock#83 to merged, or in the meanwhile we can pin manually libprotobuf to 3.21 .

Can you pin manually libprotobuf to 3.21?
I can close this PR.

I also send you a respond email regards your email you sending me about my other PRs.
Are you still wish to talk with me?

[traversaro]

Note that even if we fix compilation with new protobuf, the Windows build would still fail due to conda-forge/libignition-msgs1-feedstock#30 (that is the reason why there is a failure now only on Windows). So we need to wait also for conda-forge/libignition-msgs1-feedstock#83 to merged, or in the meanwhile we can pin manually libprotobuf to 3.21 .

Can you pin manually libprotobuf to 3.21?

I hope to fix conda-forge/libignition-msgs1-feedstock#83 soonish (1/2 days) and then fix Gazebo Classic compatibility with protobuf 4.23.2, so pinning should not be necessary.

I also send you a respond email regards your email you sending me about my other PRs.
Are you still wish to talk with me?

Sure! Unfortunatly there have been some unplanned activities that took my time, I will contact you!

[talregev]

I hope to fix conda-forge/libignition-msgs1-feedstock#83 soonish (1/2 days) and then fix Gazebo Classic compatibility with protobuf 4.23.2, so pinning should not be necessary.

Thank you for your quick respond. I am closing this PR.

[talregev]

@traversaro Why you close this PR?
conda-forge/libignition-msgs1-feedstock#83

[traversaro]

@traversaro Why you close this PR? conda-forge/libignition-msgs1-feedstock#83

It was superseded by conda-forge/libignition-msgs1-feedstock#86 , see conda-forge/conda-forge-pinning-feedstock#4502 for the context.

[traversaro]

I hope to fix conda-forge/libignition-msgs1-feedstock#83 soonish (1/2 days) and then fix Gazebo Classic compatibility with protobuf 4.23.2, so pinning should not be necessary.

Thank you for your quick respond. I am closing this PR.

Unfortunatly this turned out to be more complicated then expected, as it also required several changes deep down in google's stack (protobuf&abseil):

• CMake: Add absl::abseil_dll ALIAS target for abseil_dll abseil/abseil-cpp#1466
• CMake: Fix abseil_dll target name when using find_package(absl) protocolbuffers/protobuf#12978

Anyhow, we should be converging soonish.