Simplest way to write output message to 'output window' in Visual Studio 2010?

Question

I've tried OutputDebugString function and most of the time I get error like :

error C2664: 'OutputDebugStringA' : cannot convert parameter 1 from 'int' to 'LPCSTR'

Examples

Attempt 1:

//ERROR: sprintf is unsafe. Use sprintf_s instead
int x = 4;
char s[256];
sprintf(s, "There is %d numbers", x);
OutputDebugString((LPCWSTR)s);

Attempt 2:

//FAIL: outputs junk (sprintf_s doesn't understand unicode?)
int x = 4;
char s[256];
sprintf_s(s, "There is %d numbers", x);
OutputDebugString((LPCWSTR)s);

Attempt 3:

//ERROR: no instance of overloaded function "sprintf_s" matches the argument list
int x = 4;
TCHAR s[256];
sprintf_s(s, "There is %d numbers", x);
OutputDebugString((LPCWSTR)s);

Attempt 4:

//ERROR: no instance of overloaded function "sprintf_s" matches the argument list
int x = 4;
TCHAR s[256];
sprintf_s(s, L"There is %d numbers", x);
OutputDebugString((LPCWSTR)s);

Attempt 5:

//ERROR: no instance of overloaded function "swprintf" matches the argument list
int x = 4;
TCHAR s[256];
swprintf(s, "There is %d numbers", x);
OutputDebugString(s);

Attempt 6:

//ERROR: 'swprintf': function has been changed to confirm with the ISO C standard, adding an extra character count parameter
int x = 4;
TCHAR s[256];
swprintf(s, L"There is %d numbers", x);
OutputDebugString(s);

peter_mcc · Accepted Answer · 2010-07-05 11:53:11Z

30

It only accepts a string as a parameter, not an integer. Try something like

sprintf(msgbuf, "My variable is %d\n", integerVariable);
OutputDebugString(msgbuf);

For more info take a look at http://www.unixwiz.net/techtips/outputdebugstring.html

answered Jul 5, 2010 at 11:53

peter_mcc

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6 Comments

Billy ONeal Over a year ago

+ @Jon: Even better yet, consider using std::stringstream.

understack Over a year ago

@Billy ONeal: I used std::stringstream instead of sprintf/sprintf_s as you suggested. Thanks.

Trevor Hart Over a year ago

@BillyONeal Can you explain why using stringstream would be better? Just curious.

Billy ONeal Over a year ago

@TrevorHart Bill of 2017 doesn't wholly agree with Bill of 2010. The primary advantage is not needing to worry about the destination buffer size. But there are plenty of uses for sprintf:)

Ian Boyd Over a year ago

What do you declare msgbuf as? sprintf takes a char * and OutputDebugString takes a LPCWSTR. So i can't figure out a declaration of msgbuf that would compile.

|

Kirill V. Lyadvinsky · Accepted Answer · 2010-07-05 12:20:43Z

16

For debugging purposes you could use _RPT macros.

For instance,

_RPT1( 0, "%d\n", my_int_value );

answered Jul 5, 2010 at 12:20

Kirill V. Lyadvinsky

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Comments

Inverse · Accepted Answer · 2010-07-05 14:26:10Z

11

The most common way I'm aware of is the TRACE macro:

http://msdn.microsoft.com/en-us/library/4wyz8787%28VS.80%29.aspx

For example:

int x = 1;
int y = 16;
float z = 32.0;
TRACE( "This is a TRACE statement\n" );

TRACE( "The value of x is %d\n", x );

TRACE( "x = %d and y = %d\n", x, y );

TRACE( "x = %d and y = %x and z = %f\n", x, y, z );

answered Jul 5, 2010 at 14:26

Inverse

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1 Comment

understack Over a year ago

It seems TRACE is defined in MFC, which I'm not using.

trickymind · Accepted Answer · 2021-01-18 10:46:56Z

7

I found this answer when searching the error message: https://stackoverflow.com/a/29800589

Basically, you just need put an "L" in front of your output string when using OutputDebugString:

OutputDebugString(L"test\n");

It worked great for me.

Edit:

For formatting strings with data, I ended up using

char buffer[100];
sprintf_s(buffer, "check it out: %s\n", "I can inject things");
OutputDebugStringA(buffer);

By no means am I an expert, I just found something that worked and moved on.

edited Jan 18, 2021 at 10:46

trickymind

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answered Dec 15, 2015 at 18:20

Jangles

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3 Comments

Trevor Hart Over a year ago

That doesn't account for if I want to format the string and pass data to it.

Jangles Over a year ago

I added my solution that worked for injection. I specialize in the iOS platform and languages, please don't regard this as an expert solution :)

Richard Chambers Over a year ago

Depending on your compiler options and settings OutputDebugString is translated into one of two targets, OutputDebugStringW for wide text characters (wchart_t) or OutputDebugStringA for narrow text characters (char). The L is required for creating a wchar_t wide character string as in L"wide char" versus "narrow char". The sprintf_s() function uses narrow characters, standard char type, so the char buffer[100]; content is printed to the Output window using OutputDebugStringA() to force the use of narrow character text.

Kingeh · Accepted Answer · 2019-05-16 16:10:03Z

1

Use:

OutputDebugStringA("Some random text");

Or:

OutputDebugString("Some random text");

edited May 16, 2019 at 16:10

answered Aug 22, 2017 at 16:10

Kingeh

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1 Comment

demberto Over a year ago

2nd will not work if _UNICODE is defined

Donotalo · Accepted Answer · 2010-07-05 11:52:14Z

0

To use OutputDebugString(), provide char * or const char * as parameter:

OutputDebugString("This is an output");

answered Jul 5, 2010 at 11:52

Donotalo

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