CODEWITHSUNDEEP
c#c++visual-studiodebuggingdll
Custo
Custo

Reputation:

Debug c++ dll in C#

I have a .dll from c++ and I want to debug it in C#, but I don't know how to.

When I compiled the c++ project, Visual studio asked me to execute an ".exe".

I supposed that I had to create a project to execute the dll.

But I am lost, how could I debug it?

Upvotes: 41

Views: 34790

Answers (9)

apfreelance
apfreelance

Reputation: 34

I tried every advise here and in some other threads on SO and all over the internet, but no option worked for me to get a breakpoint inside the c++ dll hit.

Then i stumbled upon https://learn.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4747?view=msvc-170 where it says to add

#pragma unmanaged

to get rid of a warning for the entry point:

#pragma unmanaged
BOOL APIENTRY DllMain(HMODULE hModule,
    DWORD  ul_reason_for_call,
    LPVOID lpReserved
)
....

i actually only wanted to get rid of the corresponding warning, but when i started the program, i got surprised by some breakpoint inside this function finally hitting. I tried some other breakpoint inside the dll, but this did not hit. I then added the same pragma statement above the function where i had my desired breakpoint placed:

#pragma unmanaged
extern "C" _declspec(dllexport) int Add(Sample* t, int y) {
    return t->add(y); //<<<<< breakpoint
}

and the breakpoint was finally hit.

I did not find any other answer describing this, so maybe someone could either explain to me what i was doing wrong, why the pragma statement made my breakpoints hit after all and what i should do to avoid having to add a pragma statement above every function i want to debug.

I work with VS2022Community, Target Framework .NET6.0 for my c#side with Enable native code debugging activated and create a pdb on the c++side, which is inside the directory of my c# program together with the dll. From Modules i know i have the correct dll and it says Symbols loaded. However, without the pragma statement, the breakpoints were not hit.

For now, i can work with that. But it would be nice to know why the pragma statement is needed in my case, whereas other people dont mention this at all.

Upvotes: 0

Jun Ge
Jun Ge

Reputation: 420

The option "Allow unmanaged code debugging" in the "Debug" tab works for most people, but it doesn't work for me. I have to manually select "Native" as the following to debug c++ dll in my c# code. FYI: I'm using vs2019, and the dll is written with c++ and loaded into C# app with "dllimport".

enter image description here

Upvotes: 0

Gabriel Devillers
Gabriel Devillers

Reputation: 4002

To complement the useful answers by heavyd and CCicotta and Noobie3001, in Visual Studio 2017 I also had to change the following when attaching to a running C# process calling a C++ DLL: in Debug > Attach to process ..., ensure Native code is listed by Attach to:

enter image description here

Upvotes: 1

Noobie3001
Noobie3001

Reputation: 1251

I overcame this in Visual Studio 2019 by selecting "Enable native code debugging" as shown under my C# project's properies.

enter image description here

Upvotes: 7

user10044681
user10044681

Reputation: 11

For VS 2017 Pro, go to the property page of the main project (your c# project in the solution) by right mouse clicking it. At the Debug menu item, find the option in Debugger engines, choose Enable native code debugging.

Upvotes: 1

V J
V J

Reputation: 77

SOS (Son of Strike) Debugging Extension (SOS.dll) helps you debug managed code in Visual Studio by providing information about the internal CLR environment

refer the below article:-

MSDN ARTICLE

Upvotes: 0

heavyd
heavyd

Reputation: 17721

To debug a C++ from C# there a couple of things you have to do.

  1. Add a C# project to you solution for your debug application.
  2. Edit the properties of the C# project to "Allow unmanaged code debugging" on the "Debug" tab of the project properties.
  3. Set the C++ project as a dependency of the C# project.
  4. Write code in your C# project to use the DLL either using P/Invoke or COM.
  5. Set some breakpoints in your C++ code and run the C# project.

Upvotes: 22

JohnIdol
JohnIdol

Reputation: 50097

Visual Studio cannot execute a dll on its own.

You need to set the startup .exe that will be using your C++ dll in the properties of your dll project. You can do so from properties --> debugging --> command specifying the path of the executable that's gonna call your dll and any command line argument needed.

Upvotes: 5

CCicotta
CCicotta

Reputation: 605

If I understand you correctly, you want to debug a C++ coded DLL that you created, in a C# project that calls the DLL, which you also created?

I've done this before by going into your C# project properties, and under the Debug section, checking the "Enable unmanaged code debugging" check box. This should allow you to step into your C++ DLL.

Upvotes: 47

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