Don't ignore Debug profile on MSVC

[jethrogb]

Fixes #19

@alexcrichton Do you remember why you added this check?

I tested building cargo with this change and it seems to work fine.

[alexcrichton]

Trying to remember what's going on here, my guess is that the debug profile linked with /MDd or /MTd, the debug versions of the MSVC runtimes. Rust, however, currently links with either /MD or /MT which can cause incompatibilities.

I'm pretty sure this'll break some projects, but if it works for Cargo that at least means a good number should continue to work. In that sense I'm curious to see what the breakage is here, and we can always back it out if there's too much breakage!

[jethrogb]

Oh yeah I had forgotten what a mess Windows CRT is. Anyway, since cargo is statically linked that explains why cargo just works with this change. IIUC there would only ever be a problem when dynamically linking multiple build artifacts. In those cases however you'd want finer-grained control over what CRT is used anyway.

[lemon-sh]

Since CMake 3.15 the linked CRT can be controlled with the CMAKE_MSVC_RUNTIME_LIBRARY variable. Considering that AFAIK, Rust still uses exclusively non-debug variants of the MSVC CRT, it would be a good idea to bring back this behavior.

In fact I ran into this issue today, resulting in this linker error

error: linking with `link.exe` failed: exit code: 1120
  |
  = note: "C:\\Program Files (x86)\\Microsoft Visual Studio\\2022\\BuildTools\\VC\\Tools\\MSVC\\14.44.35207\\bin\\HostX64\\x64\\link.exe" "/NOLOGO" "C:\\Users\\lemon\\AppData\\Local\\Temp\\rustc8ib3fa\\symbols.o" "<39 object files omitted>" "<sysroot>\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib/{libtest-*,libgetopts-*,libunicode_width-*,librustc_std_workspace_std-*}.rlib" "C:\\Users\\lemon\\coding\\opus-rs\\target\\debug\\deps/{libopus-40066346712875d4.rlib,libaudiopus_sys-26b7af6123061671.rlib}.rlib" "<sysroot>\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib/{libstd-*,libpanic_unwind-*,libwindows_targets-*,librustc_demangle-*,libstd_detect-*,libhashbrown-*,librustc_std_workspace_alloc-*,libunwind-*,libcfg_if-*,librustc_std_workspace_core-*,liballoc-*,libcore-*,libcompiler_builtins-*}.rlib" "kernel32.lib" "kernel32.lib" "kernel32.lib" "ntdll.lib" "userenv.lib" "ws2_32.lib" "dbghelp.lib" "/defaultlib:msvcrt" "/NXCOMPAT" "/LIBPATH:C:\\Users\\lemon\\coding\\opus-rs\\target\\debug\\build\\audiopus_sys-34690a2cb6795c2d\\out/lib" "/OUT:C:\\Users\\lemon\\coding\\opus-rs\\target\\debug\\deps\\tests-0c3c6a09f807b150.exe" "/OPT:REF,NOICF" "/DEBUG" "/PDBALTPATH:%_PDB%" "/NATVIS:<sysroot>\\lib\\rustlib\\etc\\intrinsic.natvis" "/NATVIS:<sysroot>\\lib\\rustlib\\etc\\liballoc.natvis" "/NATVIS:<sysroot>\\lib\\rustlib\\etc\\libcore.natvis" "/NATVIS:<sysroot>\\lib\\rustlib\\etc\\libstd.natvis"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: LINK : warning LNK4098: defaultlib 'MSVCRTD' conflicts with use of other libs; use /NODEFAULTLIB:library␍
          libaudiopus_sys-26b7af6123061671.rlib(NLSF_stabilize.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(NLSF_VQ.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(NLSF_del_dec_quant.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(LPC_inv_pred_gain.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(burg_modified_FLP.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(NLSF_VQ_weights_laroia.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(NLSF_encode.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(NSQ_del_dec_avx2.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(VAD_sse4_1.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(NSQ.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(NSQ_del_dec.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(NLSF2A.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(process_NLSFs.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(NSQ_sse4_1.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(NSQ_del_dec_sse4_1.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(energy_FLP.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(pitch_analysis_core_FLP.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(residual_energy_FLP.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(A2NLSF.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(PLC.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(CNG.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(decode_core.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(sum_sqr_shift.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(find_pred_coefs_FLP.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(process_gains_FLP.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(wrappers_FLP.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(VAD.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(resampler_private_up2_HQ.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(stereo_find_predictor.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(LP_variable_cutoff.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(noise_shape_analysis_FLP.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(opus_encoder.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(enc_API.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(stereo_LR_to_MS.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          libaudiopus_sys-26b7af6123061671.rlib(encode_indices.obj) : error LNK2001: unresolved external symbol __imp__CrtDbgReportW␍
          C:\Users\lemon\coding\opus-rs\target\debug\deps\tests-0c3c6a09f807b150.exe : fatal error LNK1120: 1 unresolved externals␍

(While trying to cargo test in https://git.catgirls.systems/lemon/opus-rs, commit 454ee65ae9, latest as of writing this)

Interestingly, setting cmake_minimum_required to 3.1 fixes the issue, so I assume some CMake behavior must have changed in a later version?

[ChrisDenton]

Currently you need to pass /nodefaultlib:msvcrt to the linker.

The difficulty is that rustc itself only supports using msvcrt or libcm (when static linking). So if you want to use a debug CRT it's necessary to tell the linker to ignore what rust says.

[lemon-sh]

So if you want to use a debug CRT it's necessary to tell the linker to ignore what rust says.

Well, the thing is that I do not want to use the debug CRT. This is CMake configuring the project to link against it.

[UPDATE]
After digging a bit further down, it looks like since CMake 3.15 (CMP0091), specifying the CRT variant in compiler flags is no longer effective, and the aforementioned CMAKE_MSVC_RUNTIME_LIBRARY variable takes priority and must be used instead.

So from what I understand, what cmake-rs should do is set the variable to either MultiThreadedDLL or MultiThreaded, according to whether crt_static is enabled.

For reference, the workaround I'm using right now is:

let build_dir = cmake::Config::new(path)
	.define("CMAKE_MSVC_RUNTIME_LIBRARY", "MultiThreadedDLL")
	.build();

[nox]

I can confirm this is also happening with BoringSSL, which recently started requiring CMake 3.22.

[ChrisDenton]

I would be happy to accept a PR along these lines:

So from what I understand, what cmake-rs should do is set [CMAKE_MSVC_RUNTIME_LIBRARY] variable to either MultiThreadedDLL or MultiThreaded, according to whether crt_static is enabled.