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Posted 14 Oct 2001


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6 Nov 20012 min read
IPCTrace - An inter-process tracing utility

Sample Image - IPCTrace.gif


In the last few months I coded a lot of global hooks and out-of-process COM server related stuff. Global hooks are hard to debug because they're normally called in the context of the debugger process too. You can't use message boxes, etc. to report some action because this may cause your system to hang permanently under certain circumstances. There are tricks to resolve these problems (MSDN: Q179905), but I figured out problems under Windows 9x/Me. So I wrote my own inter-process tracer.

How it works

I tried to keep this tool as simple and easy to use as possible. I use the WM_COPYDATA for the IPC because this seemed to be the simplest (and fastest) way to fit my needs.

How to integrate

In order to use this IPC-tracer simply build the IPCTrace project (there are english and german resources included) and launch the application.

You should make a release build because you probably won't change any code of that project. To trace messages out of your application to the IPCTrace window I provided a macro called IPCTRACE. The definition of this macro can be found in the file IPCTraceMacros.h

#if (defined _DEBUG || defined _IPCRELEASETRACE)
#if (defined _DEBUG || defined _IPCRELEASETRACE)
#define IPCTRACE(message) \
{ \
    HWND hReceiver_CC976675_9794_4F03_B41C_FFB011BB8B8E = ::FindWindow(NULL, _T("IPCTrace")); \
    if (hReceiver_CC976675_9794_4F03_B41C_FFB011BB8B8E) \
    { \
        TCHAR szMessage[4096] = {'\0'}; \
        _stprintf(szMessage, _T("{P:%04d T:%04d} | "), ::GetCurrentProcessId(), ::GetCurrentThreadId()); \
        _tcscat(szMessage, message); \
        COPYDATASTRUCT cds; \
        ZeroMemory(&cds, sizeof(COPYDATASTRUCT)); \
        cds.dwData = 0x00007a69; \
        cds.cbData = _tcslen(szMessage) + sizeof(TCHAR); \
        cds.lpData = szMessage; \
        ::SendMessage(hReceiver_CC976675_9794_4F03_B41C_FFB011BB8B8E, WM_COPYDATA, NULL, (LPARAM) &cds); \
    } \
#else // defined _DEBUG || defined _IPCRELEASETRACE
#define IPCTRACE (void(0))
#endif // !_DEBUG

As you can see it is very simple. To use this macro include the IPCTraceMacros.h header and call the macro like this:

void CAnyClass::AnyFunc(...)
  IPCTRACE(_T("Trace this text..."))

An additional feature is that you can enable tracing in your release builds too! As you see in the code sample above you can define _IPCRELEASETRACE at the preprocessor definitions of your release build settings in order to make the macro work.

This updated version traces the corresponding process and thread ID to the output window.

In order to test this I supplied a simple client application called IPCTraceClient which is included in the package too. Try it and you'll see how it works...

If you need help with this or have suggestions how to improve it or state bugs feel free to drop me an email. Updated versions may be found at or


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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Comments and Discussions

Questionnice, but what about windows service ? Pin
MGutmann16-Aug-05 22:41
MGutmann16-Aug-05 22:41 
QuestionTRACE? Pin
Thomas Freudenberg7-Nov-01 22:26
Thomas Freudenberg7-Nov-01 22:26 
AnswerRe: TRACE? Pin
Rick York10-Nov-01 11:08
mveRick York10-Nov-01 11:08 
AnswerRe: TRACE? Pin
#realJSOP31-Jul-02 2:51
mva#realJSOP31-Jul-02 2:51 
GeneralRe: TRACE? Pin
Thomas Freudenberg31-Jul-02 2:57
Thomas Freudenberg31-Jul-02 2:57 

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