Force MetaDataGetDispenser to be linked into singlefilehost

[elinor-fung]

Add linker flags on Unix/macOS to force MetaDataGetDispenser as an undefined symbol, which makes the linker pull mscoree.o from coreclr_static. On Windows, the .def file already forces this.

Add a test that validates the export is present in the singlefilehost binary using NativeLibrary.

See #126634. We'll want to backport to 10.0.

cc @dotnet/appmodel @dotnet/dotnet-diag

[Copilot]

Pull request overview

Ensures singlefilehost continues to export MetaDataGetDispenser (regression in .NET 10 due to static-library dead-code elimination) by forcing the symbol to remain undefined at link time so the relevant object file is pulled in, and adds a regression test to validate expected exports are present.

Changes:

• Add Unix/macOS linker options to force MetaDataGetDispenser to be pulled from coreclr_static into singlefilehost.
• Add an installer test that validates key singlefilehost exports (including MetaDataGetDispenser) are present.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/native/corehost/apphost/static/CMakeLists.txt	Adds linker flags to force MetaDataGetDispenser to be linked into singlefilehost on non-Windows.
src/installer/tests/AppHost.Bundle.Tests/StaticHost.cs	Adds a test that checks singlefilehost exports on Windows (NativeLibrary) and non-Windows (nm).

[noahfalk]

Thanks!

[elinor-fung]

@copilot apply changes based on the comments in this thread

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

[am11]

Should we instead annotate these properly, e.g.:

--- a/src/coreclr/debug/runtimeinfo/runtimeinfo.cpp
+++ b/src/coreclr/debug/runtimeinfo/runtimeinfo.cpp
@@ -13,8 +13,9 @@
 #include <runtime_version.h>
 
 // Runtime information public export
-#ifdef HOST_UNIX
 DLLEXPORT
+#ifdef HOST_UNIX
+__attribute__((used, retain))
 #endif
 RuntimeInfo DotNetRuntimeInfo = {
     {

and then cleanup from various scripts like:

src/native/corehost/apphost/static/singlefilehost.def:DotNetRuntimeInfo                                   @4 data
src/native/corehost/apphost/static/singlefilehost_freebsdexports.src:DotNetRuntimeInfo
src/native/corehost/apphost/static/singlefilehost_unixexports.src:DotNetRuntimeInfo

[elinor-fung]

Maybe I'm missing something, but with just the attributes, MetaDataGetDispenser seems to no longer be retained?

--- a/src/coreclr/dlls/mscoree/mscoree.cpp
+++ b/src/coreclr/dlls/mscoree/mscoree.cpp
@@ -41,7 +41,11 @@ BOOL WINAPI DllMain(HANDLE hInstance, DWORD dwReason, LPVOID lpReserved)
 // This function gets the Dispenser interface given the CLSID and REFIID.
 // Exported from coreclr and used by external profilers.
 // ---------------------------------------------------------------------------
-STDAPI DLLEXPORT MetaDataGetDispenser(  // Return HRESULT
+STDAPI DLLEXPORT
+#ifdef HOST_UNIX
+__attribute__((used, retain))
+#endif
+MetaDataGetDispenser(  // Return HRESULT
     REFCLSID    rclsid,                 // The class to desired.

> nm -D --defined-only ./artifacts/bin/linux-x64.Release/corehost/singlefilehost
0000000000bb9340 D DotNetRuntimeInfo@@V1.0
0000000000000000 A V1.0
0000000000bc6708 B g_dacTable@@V1.0

[am11]

Ah, this is using linker script, which overrides what to keep. I wonder why linker script isn't keeping MetaDataGetDispenser as it's already there?

This workaround looks good to me, I will take a look later what can be done to make these symbols always available. I was just wondering since we used a similar linker workaround in NativeAOT BuildIntegration

runtime/src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.Unix.targets

Lines 270 to 273 in efc8c43

	<!-- this workaround can be deleted once the minimum supported glibc version
	(runtime's official build machine's glibc version) is at least 2.33
	see https://github.com/bminor/glibc/commit/99468ed45f5a58f584bab60364af937eb6f8afda -->
	<LinkerArg Include="-Wl,--defsym,__xmknod=mknod" Condition="'$(StaticExecutable)' == 'true'" />

but it was only done for the API which wasn't owned by us. 🤔