Linker errors (unresolved external symbol) building with "-Ctarget-feature=+crt-static" on x86_64-pc-windows-msvc

[gridbugs]

When building on windows with the x86_64-pc-windows-msvc toolchain, attempting to statically link the c runtime causes errors during linking.
I'm trying to build with:

cargo rustc -- -Ctarget-feature=+crt-static

During linking there are many errors about unresolved symbols, e.g.:

libspirv_cross-f48771ae5cfe7d38.rlib(spirv_cross_parsed_ir.o) : error LNK2001: unresolved external symbol __imp_isdigit

I made a repo to reproduce the problem: https://github.com/stevebob/wgpu-static-link-error
Here's the output from building on appveyor with the full error: https://ci.appveyor.com/project/stevebob/wgpu-static-link-error/build/job/xibn78580git54b2

All the linker errors begin with libspirv_cross. I thought the spirv_cross crate could be the root cause of this issue, but I can't reproduce the error by linking an app depending on just spirv_cross with +crt-static. Here's my attempt: https://ci.appveyor.com/project/stevebob/spirv-cross-windows-static-link-repro/build/job/9p7ahefakr7u3i4f

Also possibly of note, is the fact that I can successfully compile it with the x86_64-pc-windows-gnu toolchain, which my understanding is that it always statically links the c runtime: https://ci.appveyor.com/project/stevebob/wgpu-static-link-error/build/job/0ws0c9unpfouhvn8

[grovesNL]

Thanks for reporting this issue. This might be related to grovesNL/spirv_cross#109 although the missing symbols are a bit different. Could you try to trace this with a few different configurations (especially debug vs. release builds)?

[gridbugs]

Here's all combinations of debug/release, msvc/gnu, static/dynamic crt:
https://ci.appveyor.com/project/stevebob/wgpu-static-link-error/builds/29156920

I think crt-static is ignored by the gnu toolchain. The only faliures are static and msvc, and in these cases the errors are the same in debug and release mode.

[kvark]

Already presents upstream