C
C#•2w ago
yeon

How can I enforce `[StructLayout(LayoutKind.Sequential)]` metadata to be included in nuget package?

Background I have a C# library 'A' which is essentially a P/Invoke binding layer of a C++ library 'a'. And I have another C# library 'B' which depends on 'A' to add more P/Invoke functions to it. Some P/Invoke function parameters in 'B' uses the structs from 'A'. But it seems that the attribute [StructLayout(LayoutKind.Sequential)] is missing when I build a nuget package of 'A', which results in compilation error SYSLIB1051 on the 'B' side:
Runtime marshalling must be discarded in this project by applying the 'System.Runtime.CompilerService.DisableRuntimeMarshallingAttribute' to the assembly to enable marshalling this type. The generated source will not handle marshalling of parameter 'myParam'.
Is there any way to enforce [StructLayout(LayoutKind.Sequential)] to be included in the metadata of nuget package of 'A'?
8 Replies
reflectronic
reflectronic•2w ago
no, that metadata is still there why do you think that is the reason you get the error
yeon
yeonOP•2w ago
Because the decompiled code misses the attribute like this: 
#region Assembly GnsSharp.Gns.Posix64, Version=0.1.0.0, Culture=neutral, PublicKeyToken=null
// C:\Users\Home\.nuget\packages\gnssharp.gns.posix64\0.1.0-alpha.6\lib\net9.0\GnsSharp.Gns.Posix64.dll
// Decompiled with ICSharpCode.Decompiler 8.2.0.7535
#endregion

using System;

namespace GnsSharp;

//
// Summary:
//     Handle used to identify a connection to a remote host.
public struct HSteamNetConnection : IEquatable<HSteamNetConnection>, IComparable<HSteamNetConnection>
{
    public static readonly HSteamNetConnection Invalid = new HSteamNetConnection(0u);

    public uint Handle;
#region Assembly GnsSharp.Gns.Posix64, Version=0.1.0.0, Culture=neutral, PublicKeyToken=null
// C:\Users\Home\.nuget\packages\gnssharp.gns.posix64\0.1.0-alpha.6\lib\net9.0\GnsSharp.Gns.Posix64.dll
// Decompiled with ICSharpCode.Decompiler 8.2.0.7535
#endregion

using System;

namespace GnsSharp;

//
// Summary:
//     Handle used to identify a connection to a remote host.
public struct HSteamNetConnection : IEquatable<HSteamNetConnection>, IComparable<HSteamNetConnection>
{
    public static readonly HSteamNetConnection Invalid = new HSteamNetConnection(0u);

    public uint Handle;
reflectronic
reflectronic•2w ago
that is because the default is sequential if you are using LibraryImport you should add DisableRuntimeMarshallingAttribute
yeon
yeonOP•2w ago
Hmm, I can try that. But it's weird that I never needed to do that for the LibraryImport functions for 'A', but I need that for 'B'. Hmm, this is kind of annoying... Looks like to add [assembly: DisableRuntimeMarshallingAttribute] to the 'A', I need to refactor dozens of delegates which uses runtime marshalling: 
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
public delegate void FSteamNetworkingSocketsDebugOutput(ESteamNetworkingSocketsDebugOutputType type, [MarshalAs(UnmanagedType.LPUTF8Str)] string msg);

[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
public delegate void FnSteamNetConnectionStatusChanged(ref SteamNetConnectionStatusChangedCallback_t callback);
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
public delegate void FSteamNetworkingSocketsDebugOutput(ESteamNetworkingSocketsDebugOutputType type, [MarshalAs(UnmanagedType.LPUTF8Str)] string msg);

[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
public delegate void FnSteamNetConnectionStatusChanged(ref SteamNetConnectionStatusChangedCallback_t callback);
The instances of these can be passed to the native side with the Marshal.GetFunctionPointerForDelegate(). Maybe I shouldn't have had these in the first place? By the way, looks like adding [assembly: DisableRuntimeMarshallingAttribute] on the 'B' side only already solves the issue, so I could call it a day without adding that to 'A'. But that's probably not desirable?
reflectronic
reflectronic•2w ago
it is preferred to use function pointers instead of delegates. you would have to give up the marshalling, i suppose if you already have this then you don't have to add it to A. if there's no error, it doesn't make a difference
yeon
yeonOP•2w ago
I actually do provide the overloads that uses function pointers too, but I added the delegate versions too because it's hard to capture the context with function pointers. I'll just add it to B only then. Thanks for the help 🙂
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Unknown User•2w ago
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yeon
yeonOP•2w ago
Ah, thanks for letting me know

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