`libnethost.lib` appears to be built with LTCG, making it unusable with non-MSVC toolchains

[alexrp]

Description

It seems that, for Windows platforms, the libnethost.lib static library shipped with the .NET SDK is built with LTCG enabled, rendering it entirely unusable by non-MSVC toolchains such as Zig or just plain LLD on its own.

I'm not sure LTCG meaningfully benefits libnethost anyway, so I would argue it should just be disabled here.

Reproduction Steps

#define NETHOST_USE_AS_STATIC

#include "nethost.h"

int main()
{
    char_t buffer[4096];
    size_t buffer_size = sizeof(buffer) / sizeof(char_t);

    (void)get_hostfxr_path(buffer, &buffer_size, NULL);
}

zig cc test.c /path/to/libnethost.lib

Expected behavior

The program should link successfully.

Actual behavior

$ zig cc test.c libnethost.lib
lld-link: error: unknown file type: nethost\CMakeFiles\libnethost.dir\nethost.cpp.obj

Regression?

No.

Known Workarounds

Building from source with LTCG off (presumably), but this is a pretty big inconvenience.

Configuration

• .NET SDK 6.0.6
• Windows x64

Other information

No response

Tagging subscribers to this area: @vitek-karas, @agocke, @VSadov
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Issue Details

---

Description

It seems that, for Windows platforms, the libnethost.lib static library shipped with the .NET SDK is built with LTCG enabled, rendering it entirely unusable by non-MSVC toolchains such as Zig or just plain LLD on its own.

I'm not sure LTCG meaningfully benefits libnethost anyway, so I would argue it should just be disabled here.

Reproduction Steps

#define NETHOST_USE_AS_STATIC

#include "nethost.h"

int main()
{
    char_t buffer[4096];
    size_t buffer_size = sizeof(buffer) / sizeof(char_t);

    (void)get_hostfxr_path(buffer, &buffer_size, NULL);
}

zig cc test.c /path/to/libnethost.lib

Expected behavior

The program should link successfully.

Actual behavior

$ zig cc test.c libnethost.lib
lld-link: error: unknown file type: nethost\CMakeFiles\libnethost.dir\nethost.cpp.obj

Regression?

No.

Known Workarounds

Building from source with LTCG off (presumably), but this is a pretty big inconvenience.

Configuration

• .NET SDK 6.0.6
• Windows x64

Other information

No response

Author:	alexrp
Assignees:	-
Labels:	area-Host
Milestone:	-

[alexrp]

Here's how disabling LTCG is already done for other cases in the repo:

runtime/src/coreclr/dlls/mscorrc/CMakeLists.txt

Lines 7 to 9 in 663013d

	# remove /ltcg from resource-only libraries
	string(REPLACE "/LTCG" "" CMAKE_SHARED_LINKER_FLAGS_RELEASE ${CMAKE_SHARED_LINKER_FLAGS_RELEASE})
	string(REPLACE "/LTCG" "" CMAKE_SHARED_LINKER_FLAGS_RELWITHDEBINFO ${CMAKE_SHARED_LINKER_FLAGS_RELWITHDEBINFO})

If that's an acceptable fix, I can send a PR.

[vitek-karas]

Sounds reasonable - please send a PR if you can.

[alexrp]

@AaronRobinsonMSFT @vitek-karas I just realized that linking to libhostfxr.lib statically seems to be a supported scenario. Should I submit a similar PR to disable LTCG for it as well?

[AaronRobinsonMSFT]

I just realized that linking to libhostfxr.lib statically seems to be a supported scenario

I thought that was what was done here? I don't know why there would be LTCG for an import lib. Also, I didn't know an import lib scenarios even exists on non-Window.

[alexrp]

I thought that was what was done here?

The earlier PR disabled LTCG for libnethost.lib, which sits one level higher than libhostfxr.lib (you use libnethost to locate libhostfxr).

I don't know why there would be LTCG for an import lib.

lib<name>.lib is a static library; <name>.lib is an import library. I'm only talking about static libraries here. It appears that libhostfxr is being shipped as a static library in the DotNetAppHost packages just like libnethost.