[mono] Implement AssemblyExtensions.TryGetRawMetadata.

[teo-tsirpanis]

No description provided.

[jkoritzinsky]

Are you sure that this handles the hot reload case? I think this would give back the metadata for the unedited image with Mono's hot reload implementation.

[teo-tsirpanis]

I have no idea. What does CoreCLR do in hot-reloaded assemblies?

[jkoritzinsky]

For CoreCLR, we have an editable metadata system, so RefEmit and Hot Reload go down the same path (no metadata blob available to pass up to callers).

For Mono, their RefEmit solution is a completely separate lookup system, so Hot Reload uses a separate mechanism that works via "layers".

[jkoritzinsky]

So for Mono, you need to check the has_updates bit on the MonoImage. If that's true, this function needs to return false.

[teo-tsirpanis]

Done.

[jkotas]

For CoreCLR, we have an editable metadata system, so RefEmit and Hot Reload go down the same path (no metadata blob available to pass up to callers).

If I am reading the correctly, CoreCLR returns the original metadata blob for hot reload assemblies from this API.

you need to check the has_updates bit on the MonoImage.

I think it is unnecessary difference from the CoreCLR behavior. I do not see a block like this in the CoreCLR implementation.

[jkoritzinsky]

@jkotas, you're right. I was thinking of a different internal API that the implementation in CoreCLR doesn't use. The actual function it calls doesn't care about Hot Reload and just returns the original image.

[teo-tsirpanis]

Updated code to remove checks and rely on the metadata pointer not being null. This now matches the CoreCLR implementation.

runtime/src/coreclr/vm/assemblynative.cpp

Lines 1287 to 1310 in abf8e94

	extern "C" BOOL QCALLTYPE AssemblyNative_InternalTryGetRawMetadata(
	QCall::AssemblyHandle assembly,
	UINT8 **blobRef,
	INT32 *lengthRef)
	{
	QCALL_CONTRACT;
	PTR_CVOID metadata = nullptr;
	BEGIN_QCALL;
	_ASSERTE(assembly != nullptr);
	_ASSERTE(blobRef != nullptr);
	_ASSERTE(lengthRef != nullptr);
	static_assert_no_msg(sizeof(*lengthRef) == sizeof(COUNT_T));
	metadata = assembly->GetPEAssembly()->GetLoadedMetadata(reinterpret_cast<COUNT_T *>(lengthRef));
	*blobRef = reinterpret_cast<UINT8 *>(const_cast<PTR_VOID>(metadata));
	_ASSERTE(*lengthRef >= 0);
	END_QCALL;
	return metadata != nullptr;
	}