dll import with c interop using c#

a.c

__attribute__((dllexport)) void set1(int* a) {
	*a=1;
}

Makefile

a.so: a.c
	gcc -fPIC -shared -o a.so a.c

.PHONY: run
run: a.so Program.cs
	LD_LIBRARY_PATH="./;$$LD_LIBRARY_PATH" dotnet run

Program.cs

// See https://aka.ms/new-console-template for more information

using System.Runtime.InteropServices;

Console.WriteLine("Hello, World!");

[DllImport("a.so")]
static extern unsafe void set1(int* ptr);

int i = 0;
Console.WriteLine(i);

unsafe
{
	set1(&i);
}

Console.WriteLine(i);

Program.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
  </PropertyGroup>

</Project>