error LNK2001: unresolved external symbol for absl

[jingtao01]

When building from the latest 1.14.0 source code, I encountered numerous LNK2001 errors.

Here are my development environment details:

.NET version: 8.0.404
CMake version: 3.26.3
Visual Studio: 2022

I followed these steps:

1. dotnet publish Reinterop~ -o .
2. Opened Unity.
3. cmake -B build -S . -DCMAKE_BUILD_TYPE=Debug
4. cmake --build build -j14 --target install --config Debug

After completing these steps, I received multiple LNK2001 errors. Some examples include:

Could you provide any insights into why this might be occurring?

Thank you in advance for your assistance.

s2.lib(s2coords.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::LogMessageFatal(char const *,int,class absl::lts_20240722::string_view)" (??0LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@PEBDHVstring_view@23@@Z) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(r2rect.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::LogMessageFatal(char const *,int,class absl::lts_20240722::string_view)" (??0LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@PEBDHVstring_view@23@@Z) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(coder.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::LogMessageFatal(char const *,int,class absl::lts_20240722::string_view)" (??0LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@PEBDHVstring_view@23@@Z) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] CesiumGeospatial.lib(S2CellID.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::LogMessageFatal(char const *,int,class absl::lts_20240722::string_view)" (??0LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@PEBDHVstring_view@23@@Z) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(s1interval.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::LogMessageFatal(char const *,int,class absl::lts_20240722::string_view)" (??0LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@PEBDHVstring_view@23@@Z) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(s2cell_id.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::LogMessageFatal(char const *,int,class absl::lts_20240722::string_view)" (??0LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@PEBDHVstring_view@23@@Z) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(s2latlng.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::LogMessageFatal(char const *,int,class absl::lts_20240722::string_view)" (??0LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@PEBDHVstring_view@23@@Z) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(s2coords.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::~LogMessageFatal(void)" (??1LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@XZ) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(r2rect.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::~LogMessageFatal(void)" (??1LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@XZ) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(coder.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::~LogMessageFatal(void)" (??1LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@XZ) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] CesiumGeospatial.lib(S2CellID.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::~LogMessageFatal(void)" (??1LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@XZ) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(s1interval.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::~LogMessageFatal(void)" (??1LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@XZ) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(s2cell_id.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::~LogMessageFatal(void)" (??1LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@XZ) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(s2latlng.cc.obj) : error LNK2001: unresolved external symbol "public: __cdecl absl::lts_20240722::log_internal::LogMessageFatal::~LogMessageFatal(void)" (??1LogMessageFatal@log_internal@lts_20240722@absl@@QEAA@XZ) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(s2coords.cc.obj) : error LNK2001: unresolved external symbol "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > * __cdecl absl::lts_20240722::log_internal::MakeCheckOpString<__int64,__int64>(__int64,__int64,char const *)" (??$MakeCheckOpString@_J_J@log_internal@lts_20240722@absl@@YAPEAV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@_J0PEBD@Z) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] s2.lib(r2rect.cc.obj) : error LNK2001: unresolved external symbol "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > * __cdecl absl::lts_20240722::log_internal::MakeCheckOpString<__int64,__int64>(__int64,__int64,char const *)" (??$MakeCheckOpString@_J_J@log_internal@lts_20240722@absl@@YAPEAV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@_J0PEBD@Z) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj] CesiumGeospatial.lib(S2CellID.obj) : error LNK2001: unresolved external symbol "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > * __cdecl absl::lts_20240722::log_internal::MakeCheckOpString<__int64,__int64>(__int64,__int64,char const *)" (??$MakeCheckOpString@_J_J@log_internal@lts_20240722@absl@@YAPEAV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@_J0PEBD@Z) [F:\project\ttttttttttttttttttttttttttttttttt\Packages\com.cesium.unity\native~\build\Runtime\CesiumForUnityNative-Runtime.vcxproj]

[jingtao01]

I noticed there is a section in the CHANGES.md that says:
'Moved the small amount of Abseil code embedded into the s2geometry library from the absl namespace to the cesium_s2geometry_absl namespace, in order to avoid linker errors when linking against both cesium-native and the full Abseil library.'
Could this be related to the error I'm encountering?

[kring]

@jingtao01 this is most likely cause by the vcpkg abseil dependency getting out of sync. When you run the cmake configure command, you should see a message indicating the .ezvcpkg directory being used. Delete that entire directory and run configure+build again, and hopefully you won't get an error anymore.

[jingtao01]

@kring
Thank you very much for your help.
My ezpkg directory is located at D:\ezvcpkg\2024.11.16. I emptied this directory and also emptied the native~\build directory, then build and install, but I still encountered the same errors.
I noticed that in version 1.14.0, a new directory native~\vcpkg\ports\abseil was added. Some vcpkg_replace_string perations were performed.
After deleting this directory and clearing both D:\ezvcpkg\2024.11.16 and native~\build directories, the errors disappeared and the build install was successful. I am not quite sure what happened.

[kring]

Oh you know @jingtao01, I think @j9liu ran into a very similar problem in Cesium for Unreal. You should be able to fix it by modifying the absl/portfile.cmake file like this:
CesiumGS/cesium-unreal@6a44c2f

I'm not sure if you're in a position to try it now that you've solved your immediate problem, but if you do try it, please let us know if it works.

[jingtao01]

@kring
I reset git and cleared the build and ezpkg directories, then I encountered the same link error during the build process.
Then, after clearing the build and ezpkg directories and modifying absl/portfile.cmake, the build was successful without any errors. This commit indeed fixed my issue.

[kring]

Thanks @jingtao01! We'll bring that change over to Unity, too, then.