C / C++ / MFC Discussion Boards

Re: Directory

David Crow6-Mar-06 2:48

David Crow

6-Mar-06 2:48

sundar_mca wrote:
...i wanted to allocate memory for that folder...

What exactly do you mean by this?

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Problem with SQLSetEnvAttr

Amit j Patil5-Mar-06 23:49

Amit j Patil

5-Mar-06 23:49

Hello EB,
I have following Code snnipet in my Application,

SQLHENV hEnvHandle;
SQLRETURN nRet;

nRet = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &hEnvHandle);
nRet = SQLSetEnvAttr(hEnvHandle, SQL_ATTR_ODBC_VERSION, (SQLPOINTER) SQL_OV_ODBC3, SQL_IS_INTEGER);

SQLSetEnvAttr return 0 but my Debug Console window show
"First-chance exception in MyApp.exe (KERNEL32.DLL): 0xC0000005: Access Violation."

like this

sr = SQLSetStmtAttr(tempStmt, SQL_ATTR_CURSOR_TYPE, (SQLPOINTER)SQL_CURSOR_DYNAMIC, SQL_IS_INTEGER);
sr = SQLSetStmtAttr(tempStmt, SQL_ATTR_CONCURRENCY , (void *)SQL_CONCUR_LOCK, 0);
APIS also shows this exception.

What might be the cause?
Hope for Reply...
Thanks & Regards
Amit

Declare in form1.h causes error

jantimmerman5-Mar-06 23:43

jantimmerman

5-Mar-06 23:43

Hello,

I was experiencing a strange error that I tracked down to be a declaration in Form1.h
I attemped to reproduce the problem in a brand new project and to my surprise: the error appeared again.

In the new "windows forms" project

test1.cpp:

<br />
#include "stdafx.h"<br />
#include "form1.h"<br />

Added to form1.h

<br />
int test;

error:
test.obj : error LNK2005: "int test" (?test@@$$Q3HA) already defined in IncludeTest.obj
D:\VC\IncludeTest\Debug\IncludeTest.exe : fatal error LNK1169: one or more multiply defined symbols found.

I have tried int test in stdafx.h. This does compile though stdafx.h is also included in both the main and test.cpp.

Project available here (44k, created with VC++ 2005)

I thought this was according to c++ language rules, but apparently I am doing something wrong?

Best regards,
Jan Timmerman

Re: Declare in form1.h causes error

Sebastian Schneider5-Mar-06 23:46

Sebastian Schneider

5-Mar-06 23:46

If you have not already, try adding guards to your header-file.

I am not sure about your background, but each header-file should have a guard:

test1.h:

#ifndef _TEST1_H_
#define _TEST1_H_

..... your header information .....

#endif

test2.h:

#ifndef _TEST2_H_
#define _TEST2_H_

..... your header information .....

#endif

etc.

Re: Declare in form1.h causes error

Ryan Binns5-Mar-06 23:57

Ryan Binns

5-Mar-06 23:57

The problem is that memory for that variable is being allocated in every source file that includes that header file - the linker is unable to determine which one to keep and which ones to throw away. All it knows is that the two memory locations have the same name - it doesn't know that they are the same variable.

The solution is to mark the variable as extern in the header file, and declare it as normal in exactly one of the source files.

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

Re: Declare in form1.h causes error

jantimmerman6-Mar-06 1:14

jantimmerman

6-Mar-06 1:14

Perhaps that might work.
This does not explain though why it is allowed to say int test; in stdafx.h (which is included also in a lot of places)

Also I thought int test; is a declaration here. It would be illegal to write int test=3;.
I will give your suggestions a closer look, thanks for your quick replies!

-- modified at 7:47 Monday 6th March, 2006

Well, it works, thanks a lot!

Re: Declare in form1.h causes error

Ryan Binns6-Mar-06 3:10

Ryan Binns

6-Mar-06 3:10

jantimmerman wrote:
This does not explain though why it is allowed to say int test; in stdafx.h (which is included also in a lot of places)

It's because you're using precompiled headers. VC++ only compiles the header once, and just references it in all the other files that include it. If you turn off precompiled headers, you'll have the same problem there.

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

VS 2005 manifest file problem.

yourbuddy775-Mar-06 23:39

yourbuddy77

5-Mar-06 23:39

I am experiencing problems after migrating to VS 2005 from VS 2003.
The application throws up an error saying mfc80u.dll cannot be loaded. According to MSDN this problem occurs because VS 2005 generates it's own embedded manifest file so if the project already consists a manifest file,there is some problem. They suggest converting the manifest to a header and using it as #pragma comment(linker,dependency).

Require help urgently on how to convert the manifest into .h and include it in preprocesor.

thanks in advance.

Conversion from VS 6.0 to .Net

Neelesh K J Jain5-Mar-06 23:28

Neelesh K J Jain

5-Mar-06 23:28

Hello Friends,

I have an a VC++ 6.0 SDI Application and wants to convert into a .Net application. Please help me out in this conversion, I am getting lots of errors as in the stdAfx.h file I had included iostream.h file, which is required?

Help me out.

Neelesh K J Jain.

Re: Conversion from VS 6.0 to .Net

Nibu babu thomas5-Mar-06 23:36

Nibu babu thomas

5-Mar-06 23:36

you should include iostream.h likewise

#include <iostream>

and not

#include <iostream.h>

Nibu thomas
Software Developer

Re: Conversion from VS 6.0 to .Net

Christian Graus6-Mar-06 1:04

Christian Graus

6-Mar-06 1:04

As someone else said, iostream.h is not standard C++. You also need to put using namespace std; at the top of the code, as standard C++ libraries use the std namespace.

Christian Graus - Microsoft MVP - C++

Power of 2

RichardS5-Mar-06 23:23

RichardS

5-Mar-06 23:23

Hi All,

Is there a fast way of checking to see if an int is a power of 2 (i.e. 2, 4, 8, 16, 1024)? I know the long way using a loop, but I was hoping for a simple way of doing this.

regards,
Rich

"Programming today is a race between software engineers striving to build bigger and
better idiot-proof programs, and the Universe trying to produce bigger and better idiots.
So far the Universe is winning." -- Rich Cook

[Removed]

toxcct5-Mar-06 23:28

toxcct

5-Mar-06 23:28

Re: Power of 2

RichardS5-Mar-06 23:34

RichardS

5-Mar-06 23:34

Thanks

"Programming today is a race between software engineers striving to build bigger and
better idiot-proof programs, and the Universe trying to produce bigger and better idiots.
So far the Universe is winning." -- Rich Cook

Re: Power of 2

Cedric Moonen5-Mar-06 23:44

Cedric Moonen

5-Mar-06 23:44

I think you will have problems when comparinf the floats, due to the precision.

Re: Power of 2

toxcct5-Mar-06 23:46

toxcct

5-Mar-06 23:46

true, but that was a starting point.
it would be better to use double at least, but still remains the precision problem.

Re: Power of 2

Stephen Hewitt5-Mar-06 23:45

Stephen Hewitt

5-Mar-06 23:45

2^3 = 8
but
floor(sqrt(8)) != sqrt(8)?

Steve

Re: Power of 2

Stephen Hewitt6-Mar-06 2:04

Stephen Hewitt

6-Mar-06 2:04

Modified version is still wrong - It will treat any integer as a power of 2.

Steve

Re: Power of 2

toxcct6-Mar-06 2:06

toxcct

6-Mar-06 2:06

i did not pretend to modified my post for a much working stuff...

Re: Power of 2

Russell^'5-Mar-06 23:33

Russell^'

5-Mar-06 23:33

if a number is a power of 2 than looking at the bits that composed that value must be all '0' but only one '1'.
So, if int is a 32 bit value, you can look for 31 '0' and 1 '1'.
But you need olso a loop! But it is quite fast.
Let me know if here is a faster bit function to count the ones/zeros

Bye

Have a nice code day Wink | ;)

Re: Power of 2

RichardS5-Mar-06 23:38

RichardS

5-Mar-06 23:38

Yip, this was my way to begin with.

regards,
Rich

"Programming today is a race between software engineers striving to build bigger and
better idiot-proof programs, and the Universe trying to produce bigger and better idiots.
So far the Universe is winning." -- Rich Cook

Re: Power of 2

Russell^'6-Mar-06 0:11

Russell^'

6-Mar-06 0:11

Read this function, it could be another start point!
This function that I wrote last year find the bigger long, greater than the input value, that is a power of 2.
And it is quite fast! Smile | :)

unsigned long Next2Power(unsigned long x){<br />
	unsigned long y=1, x1=x;<br />
	if(x==0) return 0;<br />
	while(x1!=0){<br />
		x1>>=1;<br />
		y<<=1;<br />
	}<br />
	y>>=1;<br />
	if(y!=x) y<<=1;<br />
	return y;<br />
}

Have a nice code day Wink | ;)

Re: Power of 2

David Crow6-Mar-06 2:54

David Crow

6-Mar-06 2:54

_Russell_ wrote:
This function that I wrote last year find the bigger long, greater than the input value, that is a power of 2.

Why not just use log2()?

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: Power of 2

Russell^'6-Mar-06 4:02

Russell^'

6-Mar-06 4:02

Because my function is faster (I think) than log2().
But if I'm wrong let me know how have a faster function. And why.
thanks

Have a nice code day Wink | ;)

Re: Power of 2

David Crow6-Mar-06 5:04

David Crow

6-Mar-06 5:04

_Russell_ wrote:
...let me know how have a faster function.

This one benchmarks faster than the one you've shown:

unsigned long Next2Power(unsigned long x)
{
    x--;
    x |= x >> 1;
    x |= x >> 2;
    x |= x >> 4;
    x |= x >> 8;
    x |= x >> 16;
    x++;

    return x;
}

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

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