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I'm trying to add static library(.a) in to .Net Maui iOS application. I use functions from native binaries via DllImport attributes. So for example:

Inside .a file contains

 // add.cpp extern "C" int add(int a, int b) { return a + b; }

After creating c++ project, I am converting into .a file format like below:

g++ -c add.cpp -o add.o
ar rcs libadd.a add.o

Adding libadd.a file in to .Net MAui Application like below. Part of content of .csproj of .Net Maui sample application:

<ItemGroup>
   <!-- other declarations -->

   <NativeReference Include="Lib/libadd.a">
      <Kind>Static</Kind>
      <ForceLoad>True</ForceLoad>
      <IsCxx>True</IsCxx>
   </NativeReference>
</ItemGroup>

Inside of .cs file, I am accessing the API which is from c++ library as is shown below:

 [DllImport("__Internal", EntryPoint = "add")]
 public static extern int add(int a, int b);

I am getting these errors:

/usr/local/share/dotnet/sdk/8.0.404/Microsoft.Common.CurrentVersion.targets(2303,5): error MSB4803: The task "ResolveNativeReference" is not supported on the .NET Core version of MSBuild. Please use the .NET Framework version of MSBuild. See https://aka.ms/msbuild/MSB4803 for further details. [/Users/sadeesh.kumar/Desktop/Demo-rk/HelloWordApp/HelloWordApp.csproj::TargetFramework=net8.0-android]

/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8319/targets/Xamarin.Shared.Sdk.targets(1648,3): error : clang++ exited with code 1: [/Users/sadeesh.kumar/Desktop/Demo-rk/HelloWordApp/HelloWordApp.csproj::TargetFramework=net8.0-ios]

/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8319/targets/Xamarin.Shared.Sdk.targets(1648,3): error : ld: building for 'iOS-simulator', but linking in object file (/Users/sadeesh.kumar/Desktop/Demo-rk/HelloWordApp/Platforms/iOS/Lib/libMathFuncs.a[arm64][2](MyMathFuncs.o)) built for 'iOS' [/Users/sadeesh.kumar/Desktop/Demo-rk/HelloWordApp/HelloWordApp.csproj::TargetFramework=net8.0-ios]

/usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net8.0_18.0/18.0.8319/targets/Xamarin.Shared.Sdk.targets(1648,3): error : clang++: error: linker command failed with exit code 1 (use -v to see invocation) [/Users/sadeesh.kumar/Desktop/Demo-rk/HelloWordApp/HelloWordApp.csproj::TargetFramework=net8.0-ios]

I followed links referred below but still having the reported issue:

1.https://stackoverflow.com/questions/75126187/dllimport-with-a-file-for-ios-in-maui
2.https://learn.microsoft.com/en-us/previous-versions/xamarin/cross-platform/cpp/#stage-2-wrapping-the-native-libraries-with-a-visual-studio-solution

Environment:

  • Visual studio code: Version: 1.96.2

  • MacOS: 14.7.1

  • XCode: 16.2

  • DotNet-SDK: 8.0.404

Improve this question
1
  • 1. You can use dotnet build -v diag to query the error log2. Make sure the condition of the itemgroup is the iOS platform. 3. Make sure the target schema is compiled correctly, try to refer to native Libraries. Commented Jan 6 at 6:47
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