C / C++ / MFC

29-Jun-08 23:35

Hello everyone,

Suppose I am executing in a function, how to print values for input parameters (binary memory value is ok) using WinDbg?

(suppose I am executing in a system API, and I do not know the exact input parameter name in source code?)

thanks in advance,
George

Rajesh R Subramanian29-Jun-08 23:41

29-Jun-08 23:41

I am not sure I get your question right, but you are probably looking for OutputDebugString()[^].

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.
Codeproject.com: Visual C++ MVP

George_George30-Jun-08 1:10

30-Jun-08 1:10

Sorry Rajesh!

My bad English. I am asking if we are executing inside a function, how to print the values for input parameters for this function -- under WinDbg tool?

regards,
George

Rajesh R Subramanian30-Jun-08 1:24

30-Jun-08 1:24

I still am not getting your question correctly. I am presuming that you want to print the value of certain variables on a debug window during program execution. If I am right, then the API I linked you to will do the job.

TCHAR *szVal = _T("Hello world");
TCHAR szDbg[100];
int nVal = 100;

sprintf(szDbg, _T("szVal is [%s] nVal is [%d]"), szVal, nVal);
OutputDebugString(szDbg);

szVal = _T("Modified string");
nVal = 299;

sprintf(szDbg, _T("szVal is [%s] nVal is [%d]"), szVal, nVal);
OutputDebugString(szDbg);

The output must be visible in WinDbg window.

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.
Codeproject.com: Visual C++ MVP

George_George30-Jun-08 1:46

30-Jun-08 1:46

Thanks Rajesh,

I understand your code and what you are trying to solve. But I have not made myself understood again.

I think an example clarifies everything.

1. Suppose we are executing in function CoInitializeEx or any function which is not written by you but provided by system SDK, in which you do not know the code, only the function prototype;
2. You set a breakpoint to such system function, say CoInitializeEx, say using WinDbg tool;
3. The program debugs at CoInitializeEx, the you step into the function;
4. It is not your code which calls CoInitializeEx, but some other system functions with long call stack;
5. Now, since you are executing in function CoInitializeEx, you want to print out the input parameter value of function CoInitializeEx, how could you perform this job in WinDbg?

(you can not add code like you showed above, since you can modify code of CoInitializeEx or any sytem API function which calls CoInitializEx)

regards,
George

Rajesh R Subramanian30-Jun-08 2:15

30-Jun-08 2:15

I see your concern now. I don't know an awful lot of this, but I think that you'll need to have your own mechanism which will intercept the calls at kernel level. I *might* be totally wrong, but this[^] could get you started.

George_George wrote:
(you can not add code like you showed above, since you can modify code of CoInitializeEx or any sytem API function which calls CoInitializEx)

You probably wanted to say "cannot". Smile | :)

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.
Codeproject.com: Visual C++ MVP

George_George30-Jun-08 2:27

30-Jun-08 2:27

Thanks Rajesh,

The article describes a comprehensive solution. But I think there should be a simple solution in debugging tool.

Here are my points,

1. We can enter into any assemly language code, and see the assembly language code and watch for register and memory values;
2. If I remember correctly, if the parameter of function is small enough, the input parameters' values are stored in some specific registers, and we can print them out?
3. I roughly remember the input parameter is put around frame base pointer and we could dump the memory address aronud the frame base pointer?

I think there should be some handful commands to do such work manually -- and my purpose is just to work on it manually. Smile | :)

But after some search, I can not find exact answers.

Any comments or replies to my further description? :-P

BTW: yes, I should say can not.

regards,
George

Rajesh R Subramanian30-Jun-08 2:48

30-Jun-08 2:48

George_George wrote:
The article describes a comprehensive solution. But I think there should be a simple solution in debugging tool.

If we do it on our own, I think that it is not going to be simple. But neither am I able to think of a debugging tool or mechanism which will let you do this on a "ready-made" basis.

George_George wrote:
2. If I remember correctly, if the parameter of function is small enough, the input parameters' values are stored in some specific registers, and we can print them out?

Even if the function parameter is small enough, the location where the parameters would be stored will be dependent on the calling convention used. If it is __stdcall (WINAPI), then the function parameters would be simply pushed onto the stack (not on the registers). There is a chance that the parameters (and yes, if being small enough) will be placed on registers if the calling convention is __fastcall. But there's no guarentee, as it might depend upon availability of registers at the time of call as well.

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.
Codeproject.com: Visual C++ MVP

George_George30-Jun-08 16:03

30-Jun-08 16:03

Hi Rajesh,

Basically I agree with you. Have you tried the dv command in WinDbg? Looks it works pretty good. Smile | :)

regards,
George

Hamid_RT30-Jun-08 23:08

Hamid_RT

30-Jun-08 23:08

Do you want to print prototype of functions that you are using?

George_George30-Jun-08 23:24

30-Jun-08 23:24

No, Hamid!

I want to print out input parameters' value. Any ideas?

regards,
George

Hamid_RT1-Jul-08 21:39

Hamid_RT

1-Jul-08 21:39

Hi again,
Today I was searching for a object and on this search I found this site of course I dont see this site perfect but it has a forum for Debuggers like WinDbg and etc I guess maybe this site is helpful for you.http://www.openrce.org/forums/[^]

George_George2-Jul-08 1:42

2-Jul-08 1:42

Thanks Hamid!

I think this forum is for OllyDbg tool, not for WinDbg tool. Any comments?

regards,
George

Hamid_RT2-Jul-08 18:16

Hamid_RT

2-Jul-08 18:16

But I think I saw WinDbg on that site.

George_George6-Jul-08 3:12

6-Jul-08 3:12

Thanks Hamid,

I think there are very few posts dedicated about WinDbg, not dedicated sub-forum which deals with WinDbg. Could you check again please? Please feel free to correct me if I am wrong. Smile | :)

regards,
George

Check file in use

Karismatic29-Jun-08 23:28

Karismatic

29-Jun-08 23:28

Hi All,

I am not able to find out the solution of how to find out whether a file is ready to use or not. I have tried several ways to do this but unable to do the same, please refer me to some solution.

Regards,
Pankaj Sachdeva

There is no future lies in any job but future lies in the person who holds the job

SandipG 29-Jun-08 23:31

SandipG

29-Jun-08 23:31

Karismatic wrote:
whether a file is ready to use or not.

What does you mean by this??

Regards,
Sandip.

Saurabh.Garg29-Jun-08 23:37

Saurabh.Garg

29-Jun-08 23:37

What do you mean by file is ready?

Saurabh

Karismatic29-Jun-08 23:42

Karismatic

29-Jun-08 23:42

I mean one process in writting a file which i want to access but before I open it i want to test whether it is written completely or not. I am using this code but it is not working properly

// attempt to open existing file.
  FileHandle = CreateFile (FileName, 
                           GENERIC_READ,
                           0, 
                           NULL,
                           OPEN_EXISTING, 
                           FILE_ATTRIBUTE_NORMAL,
                           NULL);
  // if unable to open the file 
  // then return failure.
  if (FileHandle == INVALID_HANDLE_VALUE)
  {
    // return failure.
    return (FALSE);
  } // if FileHandle
  // close the open file handle.
  CloseHandle (FileHandle);
  return TRUE

Regards,
Pankaj Sachdeva

There is no future lies in any job but future lies in the person who holds the job