Libsc failes to compile with CMake on MinGW

[jmark]

Description

Compilation failes with CMake on MinGW platform. This problem is associated with creating
a t8code JLL package. See this pull request: JuliaPackaging/Yggdrasil#9718

The error output comes at llinking libsc with:
cannot find $<1:wsock32 and cannot find -lIphlpapi.
Especially, the first error output suggest that the generator expression is somehow wrong.

The used CMake version is v3.21.

The following patch solved the issue:
T/t8code/bundled/patches/libsc.patch

But it is not clear to me if this is a proper solution.

To Reproduce

For reproduction, I suggest to try to create a t8code JLL package via Yggdrasil without the application of the patches.

cd T/t8code/
julia build_tarballs.jl --debug=error --verbose x86_64-w64-mingw32-mpi+microsoftmpi

Additional information

I used Julia 1.11. But this shouldn't have any effect.

[cburstedde]

Thanks. I wouldn't mind adding a SC_WIN32 variable (with the prefix). @scivision: would that conflict with our windows builds that you usually execute?

[lukasdreyer]

I think I stumbled about a similar problem last week.

The $<1:wsock32 variables that were not found above, come from these lines in CMakeLists.txt:

target_link_libraries(sc PUBLIC
$<$<BOOL:${SC_ENABLE_MPI}>:MPI::MPI_C>
$<$<BOOL:${SC_HAVE_ZLIB}>:ZLIB::ZLIB>
$<$<BOOL:${SC_HAVE_JSON}>:jansson::jansson>
$<$<BOOL:${SC_NEED_M}>:m>
$<$<BOOL:${WIN32}>:${WINSOCK_LIBRARIES}>
)

I got a similar warning when trying to include the sc library in a cmake build, but with one of the other variables. When i replaced the <$<0 by nothing and the <$<1 by the needed variable name in the SC-targets.cmake, everything built fine.

I am not sure why the generator expression does not work here, but would replacing it by seperate target_link_libraries calls wrapped in corresponding if clauses be an option?

[scivision]

I believe this was fixed by #212
The root cause may have been missing quotes "" enclosing the generator expression when a list variable is invoked. The #212 solution of using plain if(WIN32) is clearer, equivalent, and less typo-prone.

[jmark]

Thank you all for your input! I consider this issue resolved.