C / C++ / MFC

Re: How to use listview_insertgroup with custom draw?

14-Jul-13 21:19

Have you actually tried implementing groups? As far as I can figure, it makes no difference whether this is 'standard' or owner drawn as the messages and notifications are the same. When and if I get some time I may try it myself.

Use the best guess

JoneLe8619-Jul-13 8:42

JoneLe86

19-Jul-13 8:42

thanks Richard MacCutchan for your replay,,, it seems that there are some ways Undocumented List View Features[^]
which are not documented

beginner question... recursive function

Member 1008957914-Jul-13 5:40

Member 10089579

14-Jul-13 5:40

i have this code and it works fine.

int fatt(int n)
{
    int fattoriale = 1;

    if(n==0)
        return fattoriale;
    else
        return fattoriale=n*fatt(n-1);
}

void main(void)
{
    printf("%d\n",fatt(10));

    fflush(stdin);
    getchar();
}

my question is why it works fine also here ?

int fatt(int n)
{
    int fattoriale = 1;

    if(n==0)
        return fattoriale;
    else
        fattoriale=n*fatt(n-1);
}

void main(void)
{
    printf("%d\n",fatt(10));

    fflush(stdin);
    getchar();
}

in this, there aren't the return in the else.... i am using VS2010 and compile in .c .

thanks

ps: sorry for my english

Santhosh G_14-Jul-13 7:46

Santhosh G_

14-Jul-13 7:46

In release mode it will create compilation error. It creates compilation error in VS2008. I got compilation error "error C4716: 'fatt' : must return a value".

But in debug mode it works as follows.
In both case contents of EAX register is used as the output of fatt() function. In both case EAX holds the output value, therefore the two versions works correctly in debug mode.

The result of imul is available in eax register and that is the expected result from the fatt function.

Following are the disassembly of two versions of fatt() function. First one with return value and next is without return value.

        return fattoriale=n*fatt(n-1);
01182ED2  mov         eax,dword ptr [n] 
01182ED5  sub         eax,1 
01182ED8  push        eax  
01182ED9  call        fatt (1181889h) 
01182EDE  add         esp,4 
01182EE1  imul        eax,dword ptr [n] 
01182EE5  mov         dword ptr [fattoriale],eax 
01182EE8  mov         eax,dword ptr [fattoriale]

        fattoriale=n*fatt(n-1);
01182F92  mov         eax,dword ptr [n] 
01182F95  sub         eax,1 
01182F98  push        eax  
01182F99  call        fatt (11815FAh) 
01182F9E  add         esp,4 
01182FA1  imul        eax,dword ptr [n] 
01182FA5  mov         dword ptr [fattoriale],eax

The multiplication in n*fatt(n-1) is done with imul operation. And its output is available in EAX register.

In first version( with return statement), last two instructions perform the following things. Contents of eax is moved to fattoriale and after that the contents of fattoriale is moved to eax( EAX holds the return value, or result of operation).

In second version( without return statement) the last mov is not found. But the output of iMul is in EAX register and therefore the output will be available to caller function through EAX register.

AlphaDeltaTheta14-Jul-13 17:40

14-Jul-13 17:40

Your explanation is nice but do you expect a beginner in c to understand x86 assembly?

Beauty cannot be defined by abscissas and ordinates; neither are circles and ellipses created by their geometrical formulas.

Joe Woodbury15-Jul-13 10:43

Joe Woodbury

15-Jul-13 10:43

The point is that values are returned in the eax register. The mathematical operation happens to end up with the result in eax AND eax isn't changed by any other operation. Thus it returns the right value. Problem is that something like an inline optimization could change that.

Member 1008957916-Jul-13 6:33

Member 10089579

16-Jul-13 6:33

Thanks to all! Smile | :)

I understood!

Erudite_Eric15-Jul-13 2:35

Erudite_Eric

15-Jul-13 2:35

Without the 'else' the program flow just goes to the end of the func and returns. However there is no return value, so anything calling fatt() and expecting a return value if the 'else' path is hit is going to be dissapointed.

modified 15-Jul-13 9:01am.

Re: Relocated HDD sectors

Stefan_Lang15-Jul-13 22:24

Stefan_Lang

15-Jul-13 22:24

For me, both in Debug and Release mode, the compiler (VS 2010) issues a warning for the second version, indicating the problem.

I have set Warning level to 3, and I've found that the majority of Warnings at that level indicate true errors.

My advice to beginners is:
1. Set Warning level to at least 3 (but see link below)
2. Make sure you first understand the true meaning of each Warning and what kind(s) of problem(s) it could cause at runtime. Then fix it.*

Here's an interesting article on how to deal with warnings, including those that are off by default[^].

Relocated HDD sectors

RomTibi13-Jul-13 8:20

RomTibi

13-Jul-13 8:20

I'm intending to make a program that erase an HDD. I know that modern HDDs relocate potentially deffective sectors by SMART testing, and replace with other not normally accessible. Is there a way to access ALL the sectors?

VII. 36. When you surround an army, leave an outlet free. Do not press a desperate foe too hard.
SUN-TZU - Art of War

AlphaDeltaTheta13-Jul-13 20:34

13-Jul-13 20:34

Relocation (remapping) is done transparently by the disk firmware. When a sector is detected as bad, all it's data are transferred to a special reserve area called sparse area and all further read/write attempts are redirected to it. See this wikipedia article.[^]

Sparse areas are not accessible using any standard disk access methods as all LBA addressing to it automatically redirected. (But, it is possible that there may be some vendor-specific commands to do that)

*TIP: You can use ATA Secure Erase[^] command to perform a firmware level erase of disk sectors. The GNU Shred utility is a noteworthy program using this command.

Beauty cannot be defined by abscissas and ordinates; neither are circles and ellipses created by their geometrical formulas.

Re: Relocated HDD sectors

RomTibi14-Jul-13 6:37

RomTibi

14-Jul-13 6:37

Thanks a lot. Been a SunTzu fan I also like Clausewitz very much!

VII. 36. When you surround an army, leave an outlet free. Do not press a desperate foe too hard.
SUN-TZU - Art of War

why void CView::PostNcDestroy() is called?

yu-jian12-Jul-13 22:04

yu-jian

12-Jul-13 22:04

In a project, I use the CMainFrame* pMainFrame = new CMainFrame() to create a main frame.
When the function CMainFrame::OnNcDestroy is called, void CView::PostNcDestroy()
will be called. I donot know why CView::PostNcDestroy() will be called, in the function CFrameWnd::OnCreateClient()
no new CView is created. Is there anyone know why? Thanks. Frown | :(

Re: why void CView::PostNcDestroy() is called?

pasztorpisti13-Jul-13 5:27

pasztorpisti

13-Jul-13 5:27

Use your debugger. As a first step I would put a breakpoint into CView::PostNcDestroy() and check out the callstack. There you will see who calls it and if you are lucky you can track back the reason. As a second try I would keep track of the creation of every CView and then find out which one is getting deleted.

Re: why void CView::PostNcDestroy() is called?

Erudite_Eric15-Jul-13 3:08

Erudite_Eric

15-Jul-13 3:08

Have you got an edit, scroll, list objects in your window?

http://msdn.microsoft.com/en-us/library/ws8s10w4(v=vs.80).aspx[^]

[SOLVED]Exec under windows

AlphaDeltaTheta12-Jul-13 21:01

12-Jul-13 21:01

Thinking about the fork-exec model used common in Unixes. Windows doesn't have a fork() but has all exec() counterparts. So, how does windows behave in this case? Is it similar to unix (shared ds, open fd's etc.) or in a different way?

Ans: Exec is complete alien in windows. It spawns a new process.
Tried googling but answers came mostly about unixes

Beauty cannot be defined by abscissas and ordinates; neither are circles and ellipses created by their geometrical formulas.

Richard MacCutchan12-Jul-13 22:09

12-Jul-13 22:09

In windows you create processes and/or threads[^].

Use the best guess

AlphaDeltaTheta12-Jul-13 23:08

12-Jul-13 23:08

Richard MacCutchan wrote:
In windows you create processes and/or threads[^].

I'm afraid, that's not what I asked. Being a windows developer I'm aware of the model used in windows.

Ok, then let me put my case here: I have a small unix app (written many many days ago) and now, I want to run it on windows. It has a certain case when it executes another executable with an exec() family call. This replaces the entire process with the child process, including the PID. Is this possible with the exec() family under windows?

Beauty cannot be defined by abscissas and ordinates; neither are circles and ellipses created by their geometrical formulas.

Richard MacCutchan12-Jul-13 23:18

12-Jul-13 23:18

See exec family in Windows[^].

Use the best guess

AlphaDeltaTheta12-Jul-13 23:22

12-Jul-13 23:22

Before posting this message I also went through that page, but couldn't make anything out of it, because of my .NET background. Frown | :(

Only thing that caught my eyes was this:

A program executed with one of the _exec functions is always loaded into memory as if the maximum allocation field in the program's .exe file header were set to the default value of 0xFFFFH.

Can you explain what it does? Creates a new, detached porcess or replaces it just like unix.

Beauty cannot be defined by abscissas and ordinates; neither are circles and ellipses created by their geometrical formulas.

Richard MacCutchan12-Jul-13 23:31

12-Jul-13 23:31

First sentence: Each function in this family loads and executes a new process.
You can use this either to launch an independent process that will run to completion with no interaction from the original, or you can connect to its stdin/out files for communication, or just wait for it to complete and check status. I think you can use the System.Diagnostics.Process[^] class in .NET in a similar manner.

Use the best guess

AlphaDeltaTheta13-Jul-13 16:03

13-Jul-13 16:03

Thank you.

Beauty cannot be defined by abscissas and ordinates; neither are circles and ellipses created by their geometrical formulas.

pasztorpisti13-Jul-13 8:55

pasztorpisti

13-Jul-13 8:55

Unix like fork is quite foreign in windows. Cygwin simulates fork on windows: http://stackoverflow.com/questions/985281/what-is-the-closest-thing-windows-has-to-fork[^]
There are many "unix simulation libraries" available on windows (including cygwin, interix, ...) but I wouldn't recommend building on top of these if you don't have to. My opinion about the cygwin fork simulation: In the unix world many tools/scripts make use of spawining other processes and processing data by piping the output of one process to another process. Running the same script/program "network" on windows/cygwin is multiple times slower than running the same command on linux if it involves a lot of fork invocations (for example a simple ./configure and ./make combination is always much faster on linux).