Steamworks.NET.AnyCPU v2025.162 - DownloadItemResult from Callback returns EResultNone

[Solxanich]

After updating from Steamworks.NET 20.1.0 to Steamworks.NET.AnyCPU v2025.162,

The EResult field in DownloadItemResult_t now is 0 instead of the actual result code which should be greater than 0.

Steamworks.NET.AnyCPU v2025.162 - DownloadItemResult from Callback:
https://cdn.discordapp.com/attachments/445276626352209920/1423100667110625360/image.png?ex=68df1546&is=68ddc3c6&hm=534a967c598160ebeb24c4fdd41b57ceb3263399d5f36ba3b87e815250a50c3f&

[Chicken-Bones]

It looks like there is a new and undocumented 4 byte field in DownloadItemResult_t

struct DownloadItemResult_t
{
	enum { k_iCallback = k_iSteamUGCCallbacks + 6 };
	AppId_t m_unAppID;
	uint32 unknown;
	PublishedFileId_t m_nPublishedFileId;
	EResult m_eResult;
};

and marshalling without it is causing the values to be offset.

[Chicken-Bones]

As a side note, it's difficult for us to workaround this with CallbackIdentityAttribute being internal

[Chicken-Bones]

It's an alignment issue.

[rlabrecque]

As a side note, it's difficult for us to workaround this with CallbackIdentityAttribute being internal

Can we get a quick PR for changing this piece in a way that would help you work around this? Just removing the internal? Marking it as public?

It's an alignment issue.

Do we think this is specific to AnyCPU, or

[Chicken-Bones]

Do we think this is specific to AnyCPU

Downloading the steamworks.net.2024.8.0.nupkg and decompiling the dlls in the runtimes folder shows:

Architecture	StructLayout.Pack
win-x86	8
win-x64	8
osx-x64	4
linux-x64	4

Looking into the steamworks sdk header files I find

#if defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__)
// The 32-bit version of gcc has the alignment requirement for uint64 and double set to
// 4 meaning that even with #pragma pack(8) these types will only be four-byte aligned.
// The 64-bit version of gcc has the alignment requirement for these types set to
// 8 meaning that unless we use #pragma pack(4) our structures will get bigger.
// The 64-bit structure packing has to match the 32-bit structure packing for each platform.
#define VALVE_CALLBACK_PACK_SMALL
#else
#define VALVE_CALLBACK_PACK_LARGE
#endif

I also tested the AnyCPU package on osx-x64 and osx-arm64 and had no issues.

From this we can conclude that this is only an issue with AnyCPU package on windows, and that we will somehow need to load different assemblies with different values of StructLayout for the AnyCPU package to work.

Can we get a quick PR for changing this piece in a way that would help you work around this? Just removing the internal? Marking it as public?
Changing it to public was what I had in mind, but I fear that's just leaving more landmines elsewhere in the marshalling layers, now that I know the root cause.

[Akarinnnnn]

We should completely remove Packsize usage in Any CPU(v3), and use platform default value instead. Non-windows platform default alignment value works good, as we have tested non-windows platforms are work. Since problems only occurs on win-x64, I think use platform default value for win-x64 instead hard-coded 4 would help.

If we still have issues on win-x86, we can just obsolete support of this platform.

[Akarinnnnn]

Try this to see if fixes? #738 (comment)

[Akarinnnnn]

Can we get a quick PR for changing this piece in a way that would help you work around this? Just removing the internal? Marking it as public?

Not possible for now, either change codegen deeply or sacrifice current pack workflow.

[Akarinnnnn]

I have pushed a new package version 2025.162.4 to fix your problem, try upgrade Steamworks.NET.AnyCPU to see if it fixes. win-x86 and win-x64 are tested.

Currently I packed all assemblies of different packsize into that package. But I still want to keep single universal assembly in the package, I will take effort on it.

[Akarinnnnn]

New package version 2025.162.6-a is pushed just now. This version fixes your problem by another approach: Select correct struct representation when it comes from steam, then convert it to the form you use. Please don't hesitate to have a try and provide feedback! I want to know whether it works for you.

Related PR Akarinnnnn#1 .