C / C++ / MFC

VC++ 6.0 string bug ? (take a look plz)

16-Mar-02 1:02

Try SetForegroundWindow and SetActiveWindow

Nish

My miniputt high is now 29
I do not think I can improve on that
My temperament won't hold

www.busterboy.org

Lockhart15-Mar-02 22:43

15-Mar-02 22:43

Here the SIMPLE project demo to illustrate the strange bug I noticed just some minutes ago. http://digilander.iol.it/ilbanca/fuffa/Bug.zip

Compile in Debug mode and press the button.
Compile in Release and press the button.

It beheaves in different ways (bad in Release)

The function that made me crazy:

[code]
void Buggy( char* result )
{
char s1[6];
char s2[5];

strcpy(s1,"abcde");
strcpy(s2,"BUG!");

// DOESNT WORK
strcpy(result,"anystring");
strcat(result,s1);

// THIS WAY WORKS
// strcpy(result,s1);
}
[/code]

In Debug mode works

In Release mode not
Setting 'Optimizations' to "Default" instead of "Maximixe Speed" solve the problem, but why?

I want to append 's1' to 'result', and it appends 's2' Cry | :((

((((((((

Bye.

Christian Graus15-Mar-02 22:53

Christian Graus

15-Mar-02 22:53

What is 'result', coming in ? Has it been created, or just declared ?

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

"I'm thinking of getting married for companionship and so I have someone to cook and clean." - Martin Marvinski, 6/3/2002

Lockhart15-Mar-02 23:50

15-Mar-02 23:50

void Buggy( char* result )

in the function declaration, where Buggy stores the result of the appending action.

Christian Graus15-Mar-02 23:59

Christian Graus

15-Mar-02 23:59

Yes, but do you say char * pResult; , or do you say char * pResult = new char [255]; , for example ?

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

"I'm thinking of getting married for companionship and so I have someone to cook and clean." - Martin Marvinski, 6/3/2002

Neville Franks16-Mar-02 0:33

16-Mar-02 0:33

As Christian suggests the definition of 'result' is most likely where the problem lie.

Debug builds initialize the stack, heap etc. whereas release builds don't, which is one of the reasons they behave differently.

Neville Franks, Author of ED for Windows. www.getsoft.com

Lockhart16-Mar-02 1:14

16-Mar-02 1:14

Ok.

But this is an initialization:

strcpy(result,"anystring");

Then:

strcat(result,s1);

should append 's1' to 'result', instead it appends the other string 's2' to 'result'...

it has to do with Opt/MazimixeSpeed, that in Debug build is Disabled, but for a such simple task I don't figure out why causes this strange effect...

Lockhart16-Mar-02 1:03

16-Mar-02 1:03

Yes, new char[255], is a string, vector of chars. I use Buggy() this way:

void CBugDlg::OnButton1()
{
char* test = new char[255];

Buggy(test);

m_sTest = test;

delete [] test;

UpdateData(FALSE);
}

or

void CBugDlg::OnButton1()
{
char test[255];

Buggy(test);

m_sTest = test;

UpdateData(FALSE);
}

The bug vanishes if I turn Optimizations\MaximixeSpeed to Optimizations\Default. But this still sucks... I must know why Frown | :(

Christian Graus16-Mar-02 1:06

Christian Graus

16-Mar-02 1:06

There is your problem - m_sText = test means both variables point to the same allocated data, which delete [] test will delete. You should also always set deleted pointers to NULL.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

"I'm thinking of getting married for companionship and so I have someone to cook and clean." - Martin Marvinski, 6/3/2002

Lockhart16-Mar-02 1:09

16-Mar-02 1:09

Sorry, I did not specify, but m_sTest is a CString object (DDX for a CEDit), so it copies 'test' and there should be no problems about it.

Nish Nishant16-Mar-02 1:05

16-Mar-02 1:05

are you allocating memory for result???

Nish

My miniputt high is now 29
I do not think I can improve on that
My temperament won't hold

www.busterboy.org

Lockhart16-Mar-02 1:06

16-Mar-02 1:06

Yes... try the test project if you can, try Debug and Release, pressing the button: it gives no errors, but two different outputs Frown | :(

http://digilander.iol.it/ilbanca/fuffa/Bug.zip

Nish Nishant16-Mar-02 1:18

16-Mar-02 1:18

I am puzzled.
It worked fine.
Both in release and in debug

Nish Confused | :confused:

My miniputt high is now 29
I do not think I can improve on that
My temperament won't hold

www.busterboy.org

Lockhart16-Mar-02 1:18

16-Mar-02 1:18

Grrr.... I'm running WinXP, what your OS ?

Nish Nishant16-Mar-02 3:26

16-Mar-02 3:26

Frankesk wrote:
Grrr.... I'm running WinXP, what your OS ?

I ran it on XP [both debug and release] without any problems at all.

Nish

My miniputt high is now 29
I do not think I can improve on that
My temperament won't hold

www.busterboy.org

Neville Franks16-Mar-02 9:35

16-Mar-02 9:35

Your code works fine for me as well in both Debug and Release builds on WinXP Pro. That is I "anystringabcde"

Have you tried rebooting Windows? If all else fails...

Neville Franks, Author of ED for Windows. www.getsoft.com

Lockhart16-Mar-02 9:48

16-Mar-02 9:48

This is a very strange problem...

rebooted, underclocked the processor, I have no idea... it still gives me different results:

In Debug "anystringabcde"
In Release "anystringBUG!"

When Optimizations is MazimizeSpeed(default setting)

Thanks for your time Frown | :(

Neville Franks16-Mar-02 9:53

16-Mar-02 9:53

Have you tried stepping through it in the debugger and seeing where 'result' screws up. You can still debug release builds by including debug info. I think there is an article by Mr. Newcomer here on CP about this.

Neville Franks, Author of ED for Windows. www.getsoft.com

Lockhart16-Mar-02 11:13

16-Mar-02 11:13

I have found the article, thanks! Very interesting http://www.codeproject.com/debug/survivereleasever.asp)

But life is hard: I have turned on debugging information for Release and the compiler gives me this error asa I press F5:

"Command line error D2016 : '/ZI' and '/O2' command-line options are incompatible"

/O2 is the parameter for the Optimization->MazimixeSpeed, and if I turn it OFF the bug doesn't appear, so debugging is useless in this case! Nice...

Maybe I have to reinstall, I don't know

Neville Franks16-Mar-02 11:19

16-Mar-02 11:19

You can still debug but you'll need to be able to work through the Assembler code. If you started with Assembler like I did this isn't too difficult.

Another option is to use: OutputDebugString()

Neville Franks, Author of ED for Windows. www.getsoft.com

Tim Smith16-Mar-02 12:05

Tim Smith

16-Mar-02 12:05

Debugging assembler is a dying skill. Frown | :(

Thank god I learned it years and years ago. I use that skill all the time.

Tim Smith

I know what you're thinking punk, you're thinking did he spell check this document? Well, to tell you the truth I kinda forgot myself in all this excitement. But being this here's CodeProject, the most powerful forums in the world and would blow your head clean off, you've got to ask yourself one question, Do I feel lucky? Well do ya punk?

Neville Franks16-Mar-02 12:28

16-Mar-02 12:28

Tim Smith wrote:
Debugging assembler is a dying skill.

Thank god I learned it years and years ago. I use that skill all the time.

Yes I couldn't agree more. My guess is that these days most programmers wouldn't have a clue about Assembler.

I started programming in Signetics 2650 Assembler with 8K RAM, and spent a number of years writing Z80/8080 Assembler. In fact the very first versions of my programmers editor (ED) were writtem in 2650 Assembler. It sure has come an awefully long way to what you see today. Thank god for C/C++, but having said that I still dip in to the Assembler listings from time to time while debugging.

I would also take a punt and say many developers today don't use a Debugger enough.

Neville Franks, Author of ED for Windows. www.getsoft.com

Tim Smith16-Mar-02 12:57

Tim Smith

16-Mar-02 12:57

I learned on the 8080/85, Z80, and 6809 processors.

Ah, the good old days.

My first C compiler was ECO-C. This was back in the days when a C compiler generated ASM code which you then sent into the assembler.

Tim Smith

I know what you're thinking punk, you're thinking did he spell check this document? Well, to tell you the truth I kinda forgot myself in all this excitement. But being this here's CodeProject, the most powerful forums in the world and would blow your head clean off, you've got to ask yourself one question, Do I feel lucky? Well do ya punk?

Lockhart16-Mar-02 22:56

16-Mar-02 22:56

I have a little experience with ASM, learnt at Uni and played at home, I'll give a look at it but maybe another problem has come out.

I have installed WinXP few weeks ago and I notice that no symbols are found during debugging. Maybe I have to download this 150MB package from MS site (windowsxp.x86.fre.rtm.symbols.exe)

Another strange thing appened: if I put AfxMessageBox(s1) before strcpy(), the bug vanishes:

void Buggy( char* result )
{
char s1[6];
char s2[5];

strcpy(s1,"abcde");
strcpy(s2,"BUG!");

AfxMessageBox(s1);

// DOESNT WORK
strcpy(result,"anystring");
strcat(result,s1);
}

It displays "abcde" and 'result' is filled with "anystringabcde". If I comment out AfxMessageBox(s1) 'result' is filled with "anystringBUG!".

I have made several programs, some little, others bigger, but I had never seen these strange beahviours, especially because on other PCs compiles fine. I must admit that I'm not expert in debugging, I prefer to proceed slowly, and run the program just after having added/removed some lines of code.

Lately I have installed and removed MySQL, MSDE, various ServicePacks, maybe something has been wrong and I didn't notice.

Neville Franks18-Mar-02 0:29