A question about C# invoke C++ function

Question

1.00/5 (1 vote)

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when i use dllimport to invoke C++ function as below:

C#

[DllImport("Test.dll", EntryPoint = "Init", CharSet = CharSet.Auto, CallingConvention = CallingConvention.Cdecl)]
public static extern int Init();

i use this function serveral months,after that,i add one line code in Init as below:

C++

A* a = new A();

when i use VS2010 debug Run model is ok,but when i use double click to run exe，it throw error：

Try to read or write protected memory. This usually indicates that other memory is corrupt

i can't find any problem in the code,very confuse.
so post this question and hope someone met the same question and help me to solve.
thanks!

What I have tried:

I add two messagebox as below:

C++

MessageBox(NULL,"111111！","OK!",MB_OK | MB_ICONINFORMATION);
A* a = new A();
MessageBox(NULL,"222222！","OK!",MB_OK | MB_ICONINFORMATION);

so compile code project,and double click EXE,"111111" can popup,but "22222" cann't be.
so i'm sure that new A() must be some error in.

A class consturct function as below：

C++

A::A()
{
        MessageBox(NULL,"333333！","OK!",MB_OK | MB_ICONINFORMATION);
	ctx = new des_context();
	ctx3 = new des3_context();
	bDESKeyExists = false;
	bDES3KeyExists = false;
}

i cann't see "333333" popup,very confuse,cann't find the question.

Posted 12-Jun-16 16:37pm

xuyunhai

Updated 28-Jul-17 0:54am

George Jonsson

v2

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Comments

Sergey Alexandrovich Kryukov 12-Jun-16 22:43pm

Not enough information. The exception is, most likely, thrown on the unmanaged part.
The worst thing is: you don't destruct A* a. Do you do delete a anywhere?
—SA

xuyunhai 12-Jun-16 22:46pm

i'm not destruct A* a,just to find question,so add messagebox to popup "333333",but it cann't popup "333333",so i'm very confuse and cann't find question.

Sergey Alexandrovich Kryukov 12-Jun-16 22:52pm

I can see it, but that's still a problem. Are you going to delete a?
—SA

xuyunhai 12-Jun-16 22:55pm

no, a must exist,because after new A(),i use many functions in A class.

Sergey Alexandrovich Kryukov 12-Jun-16 22:59pm

All wrong. Each new should come with delete. It depends on different factors where to delete it, but you cannot leave it. This is wrong code design in general. Please eliminate this problem.
—SA

xuyunhai 12-Jun-16 23:09pm

after i new A(),and when leave init function,i use delete A to dispose it.

Sergey Alexandrovich Kryukov 12-Jun-16 23:15pm

Better...
—SA

xuyunhai 12-Jun-16 22:56pm

why use vs2010 debug modal is ok,but complie exe and double click will post error?

Sergey Alexandrovich Kryukov 12-Jun-16 23:00pm

"debug modal"? What do you mean?
Who told you that in "Debug" you don't "compile exe"?
—SA

xuyunhai 13-Jun-16 3:13am

I mean in vs2010,i key F5 to run project

Sergey Alexandrovich Kryukov 13-Jun-16 9:40am

I understand. Please, what's the difference what you press? It builds the project, if needed, creates all assemblies which needs to be built, including your .exe, and executes it under the debugger. You can run that .exe in "Debug", instead of .exe in "Release", or any other configuration. Try to run that .exe directly, without the debugger. What happens?

Do you use threading? I'm asking because different behavior in different configurations is relatively rare and is the indication of deeper problems. Is it possible that your code is different, through using the preprocessor?

—SA

xuyunhai 12-Jun-16 22:47pm

i'm sure it must in unmanaged part,because init function i used serveral months.

George Jonsson 12-Jun-16 23:23pm

How did you compile your unmanaged DLL? As StdCall or Cdecl?
Just as an experiment set CallingConvention = CallingConvention.StdCall in your DllImport attribute.

xuyunhai 13-Jun-16 1:14am

i tried,but failed,question always exist.

George Jonsson 13-Jun-16 3:55am

You mean error, I suppose.
Well, it is not easy to give any more help.
Have you tried to remove the code inside the constructor of class A?
Like this
A::A()
{
}
Because you create some new pointers there from unknown classes.

Richard MacCutchan 13-Jun-16 5:34am

You have not shown us the code in the Init function, which is presumably where the exception occurs.

Philippe Mori 13-Jun-16 9:32am

Does all the message boxes are shown from Init function?

As others have already indicated, you do not provide enough information. In particular, it would be helpful to have Init implementation (and also specify which code is in C# and in C++).

One idea would be that there is mismatch in calling convention for your Init function but that would depend on how Init is declared and possibly your compiler options...

KarstenK 27-Jun-16 6:24am

Has your class A some members which can cause the problem?

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KarstenK · Answer 1 · 2017-07-28T00:54:00

Solution 1

Looks like the constructor of A() has some issues. Is a child class and its parent has the issue or maybe some constructors of class members.

The error message sounds like some read/write on garbage memory or pointers is done.

Build the A() as debug build and use the debugger with "step into" on the A() constructor. It works!!!

Posted 28-Jul-17 0:54am

KarstenK

Comments

Richard MacCutchan 28-Jul-17 8:11am

Look at the date of the question.