DirectPInvoke with compile time platform check

[vaind]

In an .NET library (https://github.com/getsentry/sentry-dotnet), I'm integrating a native depency ((https://github.com/getsentry/sentry-native) as a static library and linking with DirectPInvoke.
For some of the native functions, the .net code needs to call the appropriate function variant based on the platform it's running on being Windows or Linux. The problem is, with the .net library targeting net8.0 TFM, there doesn't seem to be a way to check do the conditional call that is properly resolved at link-time. This results in a link-time error when compiling for Linux, where windows-specific functions are not exported from the native library.

/usr/bin/ld.bfd: obj/Release/net8.0/linux-x64/native/Sentry.Samples.Console.Basic.o: in function `Sentry_Sentry_Native_C__sentry_options_set_database_pathw':
/home/ivan/dev/sentry-dotnet/src/Sentry/Platforms/Native/CFunctions.cs:301: undefined reference to `sentry_options_set_database_pathw'

The relevant c# code is:

        var dir = GetCacheDirectory(options);
        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
        {
            options.DiagnosticLogger?.LogDebug("Setting native CacheDirectoryPath on Windows: {0}", dir);
            sentry_options_set_database_pathw(cOptions, dir);
        }
        else
        {
            options.DiagnosticLogger?.LogDebug("Setting native CacheDirectoryPath: {0}", dir);
            sentry_options_set_database_path(cOptions, dir);
        }

....

    [DllImport("sentry-native")]
    private static extern void sentry_options_set_database_path(IntPtr options, string path);

    [DllImport("sentry-native")]
    private static extern void sentry_options_set_database_pathw(IntPtr options, [MarshalAs(UnmanagedType.LPWStr)] string path);

Additionally, static linking in consumer applications is achieved with a buildTransitive/Sentry.Native.targets file:

<Project>
  <ItemGroup Condition="$(TargetFramework.StartsWith('net8')) and '$(OutputType)' == 'Exe' And '$(RuntimeIdentifier)' == 'win-x64'">
    <DirectPInvoke Include="sentry-native" />
    <NativeLibrary Include="$(MSBuildThisFileDirectory)..\sentry-native\win-x64\sentry-native.lib" />
    <NativeLibrary Include="dbghelp.lib" />
    <NativeLibrary Include="winhttp.lib" />
  </ItemGroup>

  <ItemGroup Condition="$(TargetFramework.StartsWith('net8')) and '$(OutputType)' == 'Exe' And '$(RuntimeIdentifier)' == 'linux-x64'">
    <DirectPInvoke Include="sentry-native" />
    <NativeLibrary Include="$(MSBuildThisFileDirectory)..\sentry-native\linux-x64\libsentry-native.a" />
    <LinkerArg Include="-lcurl"/>
  </ItemGroup>

  <ItemGroup Condition="$(TargetFramework.StartsWith('net8')) and '$(OutputType)' == 'Exe' And ('$(RuntimeIdentifier)' == 'osx-x64' or '$(RuntimeIdentifier)' == 'osx-arm64')">
    <DirectPInvoke Include="sentry-native" />
    <NativeLibrary Include="$(MSBuildThisFileDirectory)..\sentry-native\osx\libsentry-native.a" />
    <LinkerArg Include="-lcurl"/>
  </ItemGroup>
</Project>

Ideally, RuntimeInformation.IsOSPlatform(OSPlatform.Windows) could be resolved as a compile-time constant and the conditional code could be trimmed completely when running on other platforms.

Or is there another way to achieve this? AFAICT, the only option I have is removing the library-specific DirectPInvoke specification and listing all symbols explicitly, omitting the single windows-specific symbol.

I've tried adding <DirectPInvoke Remove="sentry-native!sentry_options_set_database_pathw" /> to buildTransitive targets file but that doesn't seem to do anything.

[teo-tsirpanis]

Have you tried OperatingSystem.IsWindows()?

[vaind]

Have you tried OperatingSystem.IsWindows()?

So simple and yes, that actually works fine 🤦

thanks!