.NET Core Profiler Crashing on 32 bit Application Environment

Question

.NET Core Profiler Crashing on 32 bit Application Environment

Duraikannu Jeyamani 6

Hi Team.

I have developed my own .NET core profiler using VS 2019. To load my profiler, I have set the environment entry in the web.config file.
<environmentVariable name="CORECLR_ENABLE_PROFILING" value="1" />
<environmentVariable name="CORECLR_PROFILER" value="{cf0d821e-299b-5307-a3d8-b283c03916dd}" />
<environmentVariable name="CORECLR_PROFILER_PATH_64" value="C:\apps\Publish_3.0\Publish_3.0\ClrProfiler.dll" />
<environmentVariable name="CORECLR_PROFILER_PATH_32" value="C:\apps\Publish_3.0\Publish_3.0\ClrProfiler32.dll" />

I am able to profile a 64 bit .NET core application that is hosted in IIS.
But, When I try to run 32 bit .NET core application got the below exception due to my profiler.
[aspnetcorev2_inprocess.dll] Event Log: 'Application '/LM/W3SVC/5/ROOT' with physical root 'E:\netcoreapp\bin\Release\netcoreapp3.1\publish\' hit unexpected managed exception, exception code = '0xe0434352'. First 30KB characters of captured stdout and stderr logs:
Unhandled exception. System.BadImageFormatException: Bad binary signature. (0x80131192)
at net core azure.Program.Main(String[] args)
End Event Log Message.

Then I have enabled the debug logs in my .NET core profiler. The below line of code has the problem. (il_writer.cpp, 636)

Please help me why this line of code gives the problem.
![186417-capture.jpg][2]
NOTE: My Helperassembly.dll builds in AnyCPU architecture. [2]: /api/attachments/186417-capture.jpg?platform=QnA

Bruce Zhang-MSFT 3,771 Reputation points

2022-03-25T02:46:36.787+00:00

Hi @Duraikannu Jeyamani ,

When you test it in VS2019, can it run 32 bit application?

When you deploy it on IIS, how did you set IIS application pool? Did you enable 32-bit application in it?
Duraikannu Jeyamani 1 Reputation point

2024-01-17T09:15:09.99+00:00

Hi @Bruce Zhang-MSFT

Sorry for the delay response. Thank you for your understanding. When you test it in VS2019, can it run 32-bit application? No. Application not running from VS 2019 for x86 application.

When you deploy it on IIS, how did you set IIS application pool? Did you enable 32-bit application in it?
Yes. I followed the same in IIS server. Kindly give your input.

Duraikannu Jeyamani 1

Hi Team,

Do we have any update on the above issue? We are still encountering the problem when trying to monitor the 32-bit application. The issue occurs at the following functions else case:

HRESULT ILRewriter::SetILFunctionBody(unsigned size, LPBYTE pBody)

{
if (m_pICorProfilerFunctionControl != nullptr) 
{
  // We're supplying IL for a rejit, so use the rejit mechanism
IfFailRet(m_pICorProfilerFunctionControl->SetILFunctionBody(size, pBody));
} 
else 
{
  // "classic-style" instrumentation on first JIT, so use old mechanism
//Problem with the below line	  
IfFailRet(m_pICorProfilerInfo->SetILFunctionBody(m_moduleId, m_tkMethod, pBody));

}
}

1 answer

Your answer

Bruce Zhang-MSFT 3,771 Reputation points

2022-03-25T02:46:36.787+00:00

Hi @Duraikannu Jeyamani ,

When you test it in VS2019, can it run 32 bit application?

When you deploy it on IIS, how did you set IIS application pool? Did you enable 32-bit application in it?
Duraikannu Jeyamani 1 Reputation point

2024-01-17T09:15:09.99+00:00

Hi @Bruce Zhang-MSFT

Sorry for the delay response. Thank you for your understanding. When you test it in VS2019, can it run 32-bit application? No. Application not running from VS 2019 for x86 application.

When you deploy it on IIS, how did you set IIS application pool? Did you enable 32-bit application in it?
Yes. I followed the same in IIS server. Kindly give your input.
Duraikannu Jeyamani 1 Reputation point

2025-06-10T13:43:31.9666667+00:00

Hi Team,

Do we have any update on the above issue? We are still encountering the problem when trying to monitor the 32-bit application. The issue occurs at the following functions else case:

HRESULT ILRewriter::SetILFunctionBody(unsigned size, LPBYTE pBody) { if (m_pICorProfilerFunctionControl != nullptr) { // We're supplying IL for a rejit, so use the rejit mechanism IfFailRet(m_pICorProfilerFunctionControl->SetILFunctionBody(size, pBody)); } else { // "classic-style" instrumentation on first JIT, so use old mechanism //Problem with the below line IfFailRet(m_pICorProfilerInfo->SetILFunctionBody(m_moduleId, m_tkMethod, pBody)); } }

Answer 1

Tom Tran (WICLOUD CORPORATION) 260 Microsoft External Staff

Hi Duraikannu Jeyamani,

It seems that you're encountering a System.BadImageFormatException with HRESULT 0x80131192 when profiling a 32-bit .NET Core application hosted in IIS. This error typically means there's a mismatch between the architecture of the process and the DLL being loaded — for example, trying to load a 64-bit DLL into a 32-bit process or vice versa.

In your case, the crash occurs during classic-style instrumentation via SetILFunctionBody, which is sensitive to both the architecture and the validity of the IL being injected. Let's do a recap:

The error typically occurs when a 32-bit process tries to load a 64-bit DLL. Please ensure that both ClrProfiler32.dll and HelperAssembly.dll are explicitly compiled for x86. Even though HelperAssembly.dll is built as AnyCPU, it may still fail in a 32-bit process if it contains native code or platform-specific dependencies.
The crash in your profiler code at:
```
  IfFailRet(m_pICorProfilerInfo->SetILFunctionBody(m_moduleId, m_tkMethod, pBody));
```
suggests that the IL being injected might be malformed or incompatible with the method’s metadata. This API is sensitive to both the correctness of the IL and the runtime environment.
Your profiler DLLs may rely on specific versions of the Visual C++ Redistributable. If these are missing on the server, the profiler might fail to load properly due to missing dependencies.

You can try:

In Visual Studio, ensure both ClrProfiler32.dll and HelperAssembly.dll are compiled for x86:

Project Properties → Build → Platform target → x86

Guide: https://learn.microsoft.com/en-us/visualstudio/ide/how-to-configure-projects-to-target-platforms

Install Visual C++ Redistributable (x86)

Download: https://learn.microsoft.com/en-us/cpp/windows/latest-supported-vc-redist?view=msvc-170

If you're comfortable with deeper diagnostics, you can use tools like:

CorFlags to inspect DLL architecture
Fusion Log Viewer (Fuslogvw.exe) to trace assembly binding issues

These are optional and not required for most setups.

For more information, you can check out these documents below when you have the time:

Duraikannu Jeyamani 1 Reputation point

2025-06-26T10:38:46.12+00:00
Thank you @Tom Tran (WICLOUD CORPORATION) for your reply.

Here are my findings:

My application is running in 32-bit mode with a 32-bit environment entry (CORECLR_*).

My profiler DLL (xxmonitor.dll) is built with the x86 architecture.

The helper assembly is also built for the 32-bit architecture.

Please find the attachment.

However, I am still encountering the same error. Kindly provide your input so I can proceed further.

Thanks.
Duraikannu Jeyamani 1 Reputation point

2025-06-26T10:43:33.2266667+00:00

32-bit-application-Process.png Helperassembly.png
Duraikannu Jeyamani 1 Reputation point

2025-06-26T10:44:39.6366667+00:00

profiler_32bitbinary.png
Duraikannu Jeyamani 1 Reputation point

2025-06-26T10:45:25.63+00:00

Application_environmental.png
Tom Tran (WICLOUD CORPORATION) 260 Reputation points Microsoft External Staff

2025-06-27T08:44:48.18+00:00

Hi Duraikannu Jeyamani,
Thank you so much for the detailed images. But just to make sure, could you please confirm whether the Visual C++ Redistributable for x86 is installed? You can check via Control Panel → Programs and FeaturesIf you have not, then you can download it here: https://learn.microsoft.com/en-us/cpp/windows/latest-supported-vc-redist?view=msvc-170
If the issue still persists after you have downloaded it, we can proceed further to solve the issue.
Thank you.
Duraikannu Jeyamani 1 Reputation point

2025-06-30T04:54:28.3366667+00:00

Yes, we have already installed the Visual C++ Redistributable for both x86 and x64, but the issue still persists. Thank you for your help @Tom Tran (WICLOUD CORPORATION) .
Tom Tran (WICLOUD CORPORATION) 260 Reputation points Microsoft External Staff

2025-06-30T10:03:57.37+00:00

Hi Duraikannu Jeyamani,

Thank you again for your patience and for all the effort you've put into this issue. I truly appreciate how thoroughly you've followed the steps we discussed throughout the thread.

Based on everything you've shared, it looks like the behavior you're encountering may be related to deeper runtime-level interactions — particularly around IL injection and how the application is behaving under profiling conditions. These kinds of scenarios can be quite complex and often involve multiple layers of the .NET platform. I understand this may be frustrating, especially after all the work you've done, and I’m really sorry I couldn’t provide a complete resolution here.

That said, I want to make sure you’re supported moving forward. If you have a Microsoft support plan, I recommend opening a support ticket with .NET Runtime team via https://support.microsoft.com.

If not, you can also report the issue on the .NET Runtime GitHub repository in the Issues tab: https://github.com/dotnet/runtime/issues, which is free and actively monitored by Microsoft engineers. (Recommended)

I know this isn’t the outcome you were hoping for, but I hope this helps point you in the right direction. You've been a pleasure to work with, and I truly wish you the best in resolving this issue.

Warm regards,

Tom Tran

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.NET Core Profiler Crashing on 32 bit Application Environment

Hi @Bruce Zhang-MSFT

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