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OutputDebugString()

Posted on 2001-06-20
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Last Modified: 2007-11-27
In a VC6 WinAPI program, is it necessary to enclose OutputDebugString() calls in #ifdef _DEBUG blocks, or is the function removed in release builds (like with the TRACE() macro)?

If the function call (and overhead) are not removed in release mode, then does the WinAPI or CRT provide a suitable substitute?
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Question by:TookH
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by:djbusychild
ID: 6213204
the function really doesn't have to do with the "debug" mode. it simply sends strings to the debugger ( i.e. dbwin32 ) it will look for a debugger that it can hook to, if none is available it'll just not to anything. if you don't want it in your release code you should #ifdef it
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by:MichaelS
ID: 6213493
It's a fucntion (like was mentioned earlie). Usually I define another function like:

Trace(LPSTR szString)
{  
#ifndef _DEBUG
OutputDebugString(szString);
#endif
}

and I use it evrywhere in my code where I want to have some traces.
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by:jkr
ID: 6214195
You don't HAVE to guard that, but anybodz witha tracer tool will be able to see the output.

BUT:

#ifdef _DEBUG
#define ODS( x) OutputDebugString ( x)
#else
#define ODS( x)

would do it more 'globally'...
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by:TookH
ID: 6216167
jkr, I like your suggestion. I'm thinking of doing something like this:

void OutputDebug( char *s, ... )
{
    va_list argList;
    char msg[256];

    va_start( argList, s );
    vsprintf( msg, s, argList);
    va_end( argList );

    OutputDebugString( msg );
}

Then I could use a macro like yours to invoke it only in debug builds. I'm not sure if it's possible to pass variable argument lists to a macro, though. Any suggestions?
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Accepted Solution

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jkr earned 50 total points
ID: 6216211
>>I'm not sure if it's possible
>>to pass variable argument lists to a macro, though. Any
>>suggestions?

Well, you cannot use variable arguments in a macro - but you can remedy the overhead in the function calls by using

void OutputDebug( char *s, ... )
{
#ifdef _DEBUG
   va_list argList;
   char msg[256];

   va_start( argList, s );
   vsprintf( msg, s, argList);
   va_end( argList );

   OutputDebugString( msg );
#endif
}

Alternatively, you could go the way e.g. MFC does:

#ifdef _DEBUG
#define OutputDebug0( psz)                  OutputDebug     ( psz)
#define OutputDebug1( psz, p1)              OutputDebug     ( psz, p1)
#define OutputDebug2( psz, p1, p2)          OutputDebug     ( psz, p1, p2)
#define OutputDebug3( psz, p1, p2, p3)      OutputDebug     ( psz, p1, p2, p3)
#define OutputDebug4( psz, p1, p2, p3, p4)  OutputDebug     ( psz, p1, p2, p3, p4)

#else   /*  ndef _DEBUG     */

#define OutputDebug0( psz)                  ( ( void) 0)
#define OutputDebug1( psz, p1)              ( ( void) 0)
#define OutputDebug2( psz, p1, p2)          ( ( void) 0)
#define OutputDebug3( psz, p1, p2, p3)      ( ( void) 0)
#define OutputDebug4( psz, p1, p2, p3, p4)  ( ( void) 0)

#endif  /*  ndef _DEBUG     */
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by:djbusychild
ID: 6216465
you could also remedby function call overhead by making it inline. Although there's no gurantee that it'll be inline.
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Author Comment

by:TookH
ID: 6216626
I'm going to use #ifdef within the function body. If performance becomes critical, I'll switch to using the MFC method and/or djbusychild's suggestion.

Thanks everyone.
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by:nietod
ID: 6222843
Does anyone know if this accepted answer was posted as a comment or as an answer?
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by:MichaelS
ID: 6223653
As I remember it was a comment, why you are so interested in that?
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by:nietod
ID: 6224068
We're trying to measure the number of comments vs answers.

I'm putting it down as a comment for now, if you aren't really sure, let me know (or if someone else is sure.)
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by:MichaelS
ID: 6224290
I am not really sure, it's just a guess.
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by:nietod
ID: 6224305
Back into the "undecided" category....
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by:MichaelS
ID: 6224348
Somehow I think they (EE) probably sould remote answers at all, leave only comments. If it's not a secret, what is the proportion?
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by:nietod
ID: 6224508
Too early to tell, but currently 7 to 4--I think--in favor of comments.
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by:MichaelS
ID: 6224525
Well, one more question, what is the perpuse actually?
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by:jkr
ID: 6224626
It was a comment.
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by:nietod
ID: 6224854
make up your minds...  :-)
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by:TookH
ID: 6243155
It was a comment.
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