C / C++ / MFC

Re: migration from c++ 6 to Visual stutio professional 2010

19-Mar-12 16:18

Next time, post another question... but that's just a warning telling you fopen() is not safe because MS implemented their own "secure" versions of certain functions that actually validate the input to them instead of causing a crash. Of course, you can choose to do your own validation and just ignore the warnings (you can turn them off).

fopen_s:
http://msdn.microsoft.com/en-us/library/z5hh6ee9%28VS.80%29.aspx[^]

Description of security enhancements and how to disable those warnings:
http://msdn.microsoft.com/en-us/library/8ef0s5kh%28v=vs.80%29.aspx[^]

mrby12319-Mar-12 16:26

mrby123

19-Mar-12 16:26

thanks, that is useful to me.

Function Overloading

Amrit Agr18-Mar-12 5:46

Amrit Agr

18-Mar-12 5:46

Dear Developers,

Todays I found a surprsing fact on the scenario of functiona overlaoding in C++.

The code segment is here

#include <iostream>
using namespace std;

void display( char* );
void display( const char* );

void main()
{
char *ch1 = "Hello";
const char *ch2 = "Bye";

display(ch1);
display(ch2);
}

void display( char* p )
{
cout << p;
}

void display( const char* p )
{
cout << p;
}

As I know, In function overloading, the arguments must be differ in either in type or count. But its working. and one more surpring fact is that if I am remving pointers on that program. It says.. that function already have a body.

How is it possible????

Please guide me.

Thnaks.
Amrit Agrawal
Software Developer, Mumbai

Re: Function Overloading

jschell18-Mar-12 7:19

jschell

18-Mar-12 7:19

Use code tags when you post code.

What do you mean by "removing pointers"?

Amrit Agr wrote:
the arguments must be differ in either in type or count. But its working.

The arguments to the methods have different types.

And do you have warnings turned on to the highest level in your C++ compiler?

Re: Function Overloading

smags1319-Mar-12 9:25

smags13

19-Mar-12 9:25

Hi, Amrit,

It's working because it's legal to overload functions based on whether the argument refers to a const or non-const type.

So,

C++

void display(const char*) //pointer pointing to a const type

is overloading

C++

void display(char*) // plain pointer

And you're correct. The following couldn't be overloaded. It won't compile because of const conversion used by compiler. It can't figure out which one is the best match.

C++

void display(char);
void display(const char);
void display(char const);

(Technically, the above are redeclaration. It's fine to just define the third one by adding function body. But it won't compile if all of these three functions have function bodies or definitions.)

By the way, to be clearer, the following won't compiler neither because of the same reason.

C++

void display(char*){...} //plain pointer pointing to a regular type
void display(char* const){...} //const pointer pointing to a regular type

Problem with drawing using GDI functions...

Rozis18-Mar-12 0:52

Rozis

18-Mar-12 0:52

XML

I've created an application that paints on the window using GDI functions. It works fine. But because it is still under development it sometimes craches. It seems that if there are certain craches Windows Vista suddenly decides to treat my application in a new way: while drawing on the window it decides it must redraw that was on the screen when i started my application. The effect is that some drawing is lost. Windows continues with this behavour till i reboot my pc. After i booted the same piece of code draws the window correctly. I used Spy++ to find out what's happening. When the window is correctly displayed i see the following:

<00037> 00340626 P WM_LBUTTONDOWN fwKeys:MK_LBUTTON xPos:1215 yPos:640
<00038> 00340626 P WM_LBUTTONUP fwKeys:0000 xPos:1215 yPos:640
<00039> 00340626 P WM_LBUTTONDOWN fwKeys:MK_LBUTTON xPos:1249 yPos:711
<00040> 00340626 P WM_LBUTTONUP fwKeys:0000 xPos:1249 yPos:711

(I press the mousebutton to start drawing, it draws the window, i press the mousebutton again to close the window)

When things go wrong Spy++ reports the following:

<00037> 00340626 P WM_LBUTTONDOWN fwKeys:MK_LBUTTON xPos:1219 yPos:643
<00038> 00340626 P WM_LBUTTONUP fwKeys:0000 xPos:1219 yPos:643
<00039> 004904B2 S WM_WINDOWPOSCHANGING lpwp:0012FE20
<00040> 004904B2 R WM_WINDOWPOSCHANGING
<00041> 004F0646 S WM_WINDOWPOSCHANGING lpwp:0012FE20
<00042> 004F0646 R WM_WINDOWPOSCHANGING
<00043> 00340626 S WM_WINDOWPOSCHANGING lpwp:0012FE20
<00044> 00340626 R WM_WINDOWPOSCHANGING
<00045> 004904B2 S WM_WINDOWPOSCHANGED lpwp:0012FE20
<00046> 004904B2 R WM_WINDOWPOSCHANGED
<00047> 004F0646 S WM_WINDOWPOSCHANGED lpwp:0012FE20
<00048> 004F0646 R WM_WINDOWPOSCHANGED
<00049> 00340626 S WM_WINDOWPOSCHANGED lpwp:0012FE20
<00050> 00340626 S .WM_SIZE fwSizeType:SIZE_RESTORED nWidth:1280 nHeight:770
<00051> 00340626 R .WM_SIZE
<00052> 00340626 R WM_WINDOWPOSCHANGED
<00053> 004904B2 S WM_WINDOWPOSCHANGING lpwp:0012FE20
<00054> 004904B2 R WM_WINDOWPOSCHANGING
<00055> 004F0646 S WM_WINDOWPOSCHANGING lpwp:0012FE20
<00056> 004F0646 R WM_WINDOWPOSCHANGING
<00057> 00340626 S WM_WINDOWPOSCHANGING lpwp:0012FE20
<00058> 00340626 R WM_WINDOWPOSCHANGING
<00059> 00340626 P WM_PAINT hdc:00000000
<00060> 00340626 S WM_ERASEBKGND hdc:D1011D9A
<00061> 00340626 R WM_ERASEBKGND fErased:False
<00062> 00340626 S WM_GETICON fType:True
<00063> 00340626 R WM_GETICON hicon:1CA203B1
<00064> 00340626 S WM_GETICON fType:False
<00065> 00340626 R WM_GETICON hicon:00000000
<00066> 00340626 S WM_GETICON fType:True
<00067> 00340626 R WM_GETICON hicon:089A0417
<00068> 00340626 P WM_LBUTTONDOWN fwKeys:MK_LBUTTON xPos:1252 yPos:726
<00069> 00340626 P WM_LBUTTONUP fwKeys:0000 xPos:1252 yPos:726

The big difference is lines numbered 39-67. Does anyone understand what's happening here? And what is a correct solution for this problem? What causes it? It seems that i have to intercept the paint message to tell Windows to shut up. But what worries me is that the hdc is 0. 

Any help will be appreciated..

Re: Problem with drawing using GDI functions...

Albert Holguin18-Mar-12 17:09

Secure erase command implementation

18-Mar-12 17:09

That just looks like the window position is getting changed. Hard to say what may be wrong from just looking at the messages that Windows is sending your applications window. You probably need to post some of the applicable code.

K4HVDs18-Mar-12 0:19

K4HVDs

18-Mar-12 0:19

I read about Secure erase command that has been implemented in HDD firmware after 2006, under T13 commitee authority. Can this command be invoked from a MFC program?

Re: Secure erase command implementation

jschell18-Mar-12 7:23

jschell

18-Mar-12 7:23

C/C++ programs can call any API exposed either via the OS or other applications.

They can also invoke assembly. Even if the MS compilers do not support embedded assembly (I didn't look) one can still invoke assembly via a function pointer cast.

So basically if your equipment supports it then it can be called in C/C++. Doesn't mean it is easy though.

Re: Secure erase command implementation

Albert Holguin18-Mar-12 17:28

Re: Multiple threads in MFC

18-Mar-12 17:28

As jschell suggested, you can probably get tricky and get it accomplished one way or another, but by default, you should assume that the functionality will not be easily accessible unless made available by the hardware driver. Look for a drive that supports it and see if they have their own driver (as opposed to a generic HDD driver which is likely not to have this function) and have an API that allows you to access it.

Multiple threads in MFC

K4HVDs18-Mar-12 0:15

K4HVDs

18-Mar-12 0:15

1. Can anybody show me an example on running multiple threads from an MFC application?
2. Is this possible in VS6?
...
Thanks in advance Rose | [Rose]

Jochen Arndt18-Mar-12 1:23

Jochen Arndt

18-Mar-12 1:23

There are many examples on the net and here like this one: Introduction to Multi-threaded Code [^].

Re: Multiple threads in MFC

Rajesh R Subramanian18-Mar-12 2:47

Rajesh R Subramanian

18-Mar-12 2:47

I think what you need is a good book. I'd recommend Programming Windows with MFC[^]

"Real men drive manual transmission" - Rajesh.

Re: Multiple threads in MFC

Albert Holguin18-Mar-12 17:13

18-Mar-12 17:13

This is for VS2003, but if I recall correctly, nothing changed from VS6 to 2003 in regards to threading:
http://msdn.microsoft.com/en-us/library/975t8ks0%28v=vs.71%29.aspx[^]

Little advice of CFront

Brandon-X1200017-Mar-12 17:13

17-Mar-12 17:13

Hello all,

I'm coding CFront, the very first form of C++, I have the .pdf file and using the compiler Code::Blocks, but I'm confused, should I use a project or just code it as file(s) individuality.

Also, how do I "identify" all the source code, in other words, what do I call which file what in order to avoid programming errors, like the .pdf has all the info in it, but as you can see I'm a "precise" person, and don't like to have errors OR tend to make errors a lot.

Richard MacCutchan17-Mar-12 22:07

Richard MacCutchan

17-Mar-12 22:07

Brandon T. H. wrote:
as you can see I'm a "precise" person

Who posts vague questions.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Brandon-X1200017-Mar-12 23:22

17-Mar-12 23:22

Just telling you, I tend to make errors a lot, and I need help to see if I'm doing this right (coding CFront). Smile | :)

Richard MacCutchan18-Mar-12 2:14

Richard MacCutchan

18-Mar-12 2:14

Have another look at this section[^] with particular reference to point 2.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Brandon-X1200018-Mar-12 6:39

18-Mar-12 6:39

Richard MacCutchan wrote:
particular reference to point 2

Yeah, you have to be specific, I'm trying to make this clear as much as possible.

The .pdf file has code in it along with other stuff (like file names, heading names, comments, images, pictures, etc.), All I'm asking for is where do I find the header names and all the configuration in all that jargon, so I'm coding this right (because all that code does not go into one header). Please be aware I'm typing 300 pages, manually or one-by-one.

Simple Regards,
Brandon

modified 18-Mar-12 12:56pm.

Richard MacCutchan18-Mar-12 22:31

Richard MacCutchan

18-Mar-12 22:31

Brandon T. H. wrote:
The .pdf file has code in it

What exactly are you trying to create from this? I've had a quick look in this file and it looks like the listing of a complete C/C++ library. It's also dated 1985 so I guess it's out of date.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Brandon-X1200020-Mar-12 10:09

20-Mar-12 10:09

A CFront compiler

Simple Regards,
Brandon

markkuk18-Mar-12 0:08

markkuk

18-Mar-12 0:08

Pass the PDF file through an OCR[^] program to convert it into plain text, then split the file into individual source files, remove page headers and footers, fix scanning and OCR errors and you end up with files that might be acceptable to a C compiler.

Brandon-X1200018-Mar-12 6:45