RuntimeAsync failed to run on aarch64 linux with dotnet10 rc

[fallenwood]

Description

Error message

dotnet run
Unhandled exception. System.TypeLoadException: Could not load type 'Program' from assembly 'test, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' because the format is invalid.

Reproduction Steps

code

await TestAsync();
async Task TestAsync() {
  await Task.Yield();
}

csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net10.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
    <Features>$(Features);runtime-async=on</Features>
    <NoWarn>SYSLIB5007</NoWarn>
  </PropertyGroup>
</Project>

run dotnet run

Expected behavior

It should not throw exceptions

Actual behavior

Could not load type 'Program' from assembly

Regression?

No response

Known Workarounds

N/A

Configuration

dotnet --version
10.0.100-rc.1.25451.107

lscpu

Architecture:                aarch64
  CPU op-mode(s):            32-bit, 64-bit
  Byte Order:                Little Endian
CPU(s):                      4
  On-line CPU(s) list:       0-3
Vendor ID:                   ARM
  Model name:                Cortex-A53
    Model:                   4
    Thread(s) per core:      1
    Core(s) per cluster:     4
    Socket(s):               -
    Cluster(s):              1
    Stepping:                r0p4
    CPU(s) scaling MHz:      50%
    CPU max MHz:             1200.0000
    CPU min MHz:             600.0000
    BogoMIPS:                38.40
    Flags:                   fp asimd evtstrm crc32 cpuid
Caches (sum of all):
  L1d:                       128 KiB (4 instances)
  L1i:                       128 KiB (4 instances)
  L2:                        512 KiB (1 instance)
Vulnerabilities:
  Gather data sampling:      Not affected
  Ghostwrite:                Not affected
  Indirect target selection: Not affected
  Itlb multihit:             Not affected
  L1tf:                      Not affected
  Mds:                       Not affected
  Meltdown:                  Not affected
  Mmio stale data:           Not affected
  Reg file data sampling:    Not affected
  Retbleed:                  Not affected
  Spec rstack overflow:      Not affected
  Spec store bypass:         Not affected
  Spectre v1:                Mitigation; __user pointer sanitization
  Spectre v2:                Not affected
  Srbds:                     Not affected
  Tsx async abort:           Not affected

uname

Linux pi 6.14.0-1013-raspi dotnet/runtime#13-Ubuntu SMP PREEMPT_DYNAMIC Tue Aug 19 13:57:45 UTC 2025 aarch64 aarch64 aarch64 GNU/Linux

Other information

No response

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[jakobbotsch]

To use runtime async DOTNET_RuntimeAsync=1 must be set in the environment.

[fallenwood]

To use runtime async DOTNET_RuntimeAsync=1 must be set in the environment.

Thanks for replying. The error message changed with this environment variable set, but it still fails

bash-5.2$ DOTNET_RuntimeAsync=1 dotnet ./bin/Debug/net10.0/test.dll
Unhandled exception. System.InvalidProgramException: Common Language Runtime detected an invalid program.
   at Program.<Main>$(String[] args)
   at Program.<Main>(String[] args)
Aborted (core dumped)

bash-5.2$ DOTNET_RuntimeAsync=1 dotnet run
Unhandled exception. System.InvalidProgramException: Common Language Runtime detected an invalid program.
   at Program.<Main>$(String[] args)
   at Program.<Main>(String[] args)

Also I found it also fails on linux x64, but works on windows x64 without this variable also fails

[hez2010]

It seems to be a roslyn bug.
With runtime async you cannot use await in the top-level statements otherwise you will encounter the Common Language Runtime detected an invalid program issue. Instead you can wrap it into an async method and call it manually:

Wrapper().GetAwaiter().GetResult();

async Task Wrapper()
{
    await TestAsync();
    async Task TestAsync() {
      await Task.Yield();
    }
}

or don't use top-level statements at all:

class Program
{
    static async Task Main()
    {
        await TestAsync();
        async Task TestAsync() {
          await Task.Yield();
        }
    }
}

/cc: @jcouv

[jcouv]

@333fred Could you take a look and move to roslyn if appropriate? Seems like an issue with runtime-async with top-level statements.

[333fred]

Thanks for the report. The MethodImplAttributes.Async bit was missed for top-level statements here.