creating log file win 32

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C++

void dshowCapture::initlogfile()
{
    /////////log file initialization////    
    TCHAR dwDirectory[256];
    TCHAR capturelogfile[256];
    ZeroMemory(dwDirectory, sizeof(dwDirectory));
    ZeroMemory(capturelogfile, sizeof(capturelogfile));
    GetCurrentDirectory(256, dwDirectory);
    strcpy (capturelogfile,dwDirectory);	
    strcat(capturelogfile,"\\CaptureLog.txt");

    std::ofstream *fs;
    fs=new	std::ofstream(capturelogfile); 

    char *log="helow";

    for(int i=0;i<1000;i++)
    fs->write(log,sizeof(log));

    fs->close();
    delete fs;

}

Is this correct implementation because program runs but after

C++

std::ofstream *fs;
fs=new	std::ofstream(capturelogfile);

near about 48 bytes and after execution of for loop 50 bytes increase

after delete operation memory remains to that increased value(near abt 100 bytes)

Posted 29-Jan-12 3:01am

pranav_30

Updated 29-Jan-12 5:01am

Richard MacCutchan

v2

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Addy Tas · Accepted Answer · 2012-01-29T04:19:00

Solution 1

Hi,

Though I have a number of comments to the code like making TCHAR arrays and using strcpy in stead of _tcscpy or bettery yet _tcscpy_s and apparently you are ok wiht writing the size of a pointer (good thing you're not using 64 bits in this case) to the file; I can't directly see a memory leak appearing.

Note that if your app is leaking you will most likely see a "dumping normal block" notification in the output window when closing the app.

Cheers,

AT.

Posted 29-Jan-12 4:19am

Addy Tas

Comments

pranav_30 29-Jan-12 10:39am

thx shal i use
Char instead of Tchar..
Ok i wl replace that strcpy

And after terminatng program output winow is ok means no mem leak detected..

Any further sugetn plz..

Mohibur Rashid 29-Jan-12 11:06am

the difference between char and wchar_t (TCHAR) is char is single byte and wchar_t is two bytes long.

pranav_30 29-Jan-12 11:39am

ok thanks... so i think i dont required to use TCHAR ..
i replace it with char :)

Addy Tas 29-Jan-12 16:59pm

Make sure to replace the sizeof(log) by a strlen(log); you're now writing the sizeof pointer to the file.

Addy Tas 29-Jan-12 17:08pm

Almost forgot; the TCHAR can be either one or two bytes of size, this depends on if you have _UNICODE defined. In the VS project settings you have a entry for use TCHAR as....
If you use TCHAR in one place, make sure that all the manipulation calls (strlen etc.) reflect the same.

Cheers, AT

Mohibur Rashid 29-Jan-12 22:12pm

I will argue with you about that, TCHAR is always two bytes and Never One byte,

If you define _UNICODE it will force compiler to choose Wide Character version of Function, As Example CreateWindow, _UNICODE Is defined then Macro will define CreateWindowW, CreateWindowA otherwise.

Addy Tas 30-Jan-12 2:27am

Hi,
To argument is always good (unless you need to catch a train) as it is an opportunity to lean something.
I took the following from winnt.h (VS 2005) so it seems that my TCHAR is still one byte.

#ifdef UNICODE // r_winnt

#ifndef _TCHAR_DEFINED
typedef WCHAR TCHAR, *PTCHAR;
typedef WCHAR TBYTE , *PTBYTE ;
#define _TCHAR_DEFINED
#endif /* !_TCHAR_DEFINED */

typedef LPWSTR LPTCH, PTCH;
typedef LPWSTR PTSTR, LPTSTR;
typedef LPCWSTR PCTSTR, LPCTSTR;
typedef LPUWSTR PUTSTR, LPUTSTR;
typedef LPCUWSTR PCUTSTR, LPCUTSTR;
typedef LPWSTR LP;
#define __TEXT(quote) L##quote // r_winnt

#else /* UNICODE */ // r_winnt

#ifndef _TCHAR_DEFINED
typedef char TCHAR, *PTCHAR;
typedef unsigned char TBYTE , *PTBYTE ;
#define _TCHAR_DEFINED
#endif /* !_TCHAR_DEFINED */

typedef LPSTR LPTCH, PTCH;
typedef LPSTR PTSTR, LPTSTR, PUTSTR, LPUTSTR;
typedef LPCSTR PCTSTR, LPCTSTR, PCUTSTR, LPCUTSTR;
#define __TEXT(quote) quote // r_winnt

#endif /* UNICODE */ // r_winnt

Mohibur Rashid 30-Jan-12 3:15am

Thank you for your reply,

please take a look at the code below
#include <windows.h>
#include <iostream>
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
#ifdef UNICODE
cout<<sizeof(TCHAR)<<endl;
#undef UNICODE
#endif
#ifndef UNICODE
cout<<sizeof(TCHAR)<<endl;
#endif
return 0;
}

also take a look at the code portion taken from tchar.h file

#ifndef _TCHAR_DEFINED
#if !__STDC__
typedef wchar_t TCHAR;
#endif
#define _TCHAR_DEFINED
#endif

#define _TEOF WEOF

#define __T(x) L ## x

Mohibur Rashid 30-Jan-12 3:16am

In the first code it shows the size of TCHAR is always 2 bytes, whether UNICODE is defined or not

Addy Tas 30-Jan-12 3:29am

Hi,

Now I knew you were going to mention and kind of wanted to put this in the previous comment but as it is always nice to have a constructive argument:

Check out line 168 in the tchar.h, just a couple of lines above the TCHAR definition, then the the #else is @ line 838 followed by the char definition on line 1246.

Your example seems fine at first but you have to remember also to undefine the _TCHAR_DEFINED to change the type of the TCHAR.

Cheers,

AT

Mohibur Rashid 30-Jan-12 3:37am

You are absolutely right, I did not continue checking the file. and My Example program also vein,
If user select Character Set to Not set then the size of the TCHAR will be 1.
else If Set To Unicode then TCHAR size is 2 byte
else if Set To Multibyte then TCHAR size is 1 byte.

My example is pointless because: the definition of TCHAR is constructed long before I undef the UNICODE Macro. That is why it has no actual impact on size of TCHAR.

Anyway, I also understand I have mixed up TCHAR with wchar_t

Addy Tas 30-Jan-12 3:48am

Hi,

You are entirely right; TCHAR is defined in the pre-compile stage which makes runtime changes a bit... well odd.
TCHAR can be really handy for having code that can work single and MBCS or Unicode but better make sure you know what you're doing or you might be accessing something that's not there.

Cheers,

AT

pranav_30 30-Jan-12 1:25am

well i used char dwDirectory[256];
strcpy_s();
&
fs->write(log,strlen(log));

:)

Addy Tas 30-Jan-12 6:18am

Hi,

If this is all working for you be so kind to accept / upvote the answer so the item will no longer appear on the open issues.
If you have more questions; all you need to do is ask :)

Cheers, AT