C / C++ / MFC

Richard MacCutchan2-May-20 22:11

2-May-20 22:11

Yes, but Func() is not really necessary, since you have already declared S. You can just say S.x = 100;

Creating a function to return a structure (or anything else) is usually necessary when you cannot declare the relevant object at compile time, but need to create it dynamically. Something like:

C++

TestStruct* Funct()
{
    TestStruct* pS = new TestStruct;
    pS->x = 0;
    ps->z = 0;
    // other initialisation code
    
    return pS;
}

//
TestStruct* pNewStruct = Funct();
pNewStruct->x = 100;

Stephane Capo2-May-20 22:19

Stephane Capo

2-May-20 22:19

Hello,

the code itself will work, but will not do what I suppose you expect.

Here, Funct returns a copy of the TestStruct S.

So Funct().x = 100 will affect 100 in a temporary TestStruct that you can not use after that.

I don't know why you want to use a function to access your S structure, but the behavior you look for is probably :

C++

// Funct returns a reference on S structure.
   TestStruct& Funct()
   {
       return S;
   }

Calin Negru2-May-20 22:50

2-May-20 22:50

my actual code:

ChartNode Chart[100];
ChartNode NodeCoord(int x, int z)
{
	return Chart[z * 10 + x];
} 


if(NodeCoord(4,4).access)
//do something 
NodeCoord(4,4).access = false;

The result I`m looking for is the same as the result achieved with this function:

void NodeCoord(int x, int z, bool writetobool)
{
 Chart[z * 10 + x].access = writetobool;
}

modified 3-May-20 5:10am.

Stephane Capo2-May-20 23:03

Stephane Capo

2-May-20 23:03

So you probably need to return a reference :

C++

ChartNode& NodeCoord(int x, int z)
{
     return Chart[z * 10 + x];
}

else the NodeCoord(4,4).access = false will assign a temporary copy of your ChartNode struct and not the one in your array.

Calin Negru2-May-20 23:13

2-May-20 23:13

ChartNode& NodeCoord() will work for both read and write?

Stephane Capo2-May-20 23:51

Stephane Capo

2-May-20 23:51

Yes.

Richard MacCutchan2-May-20 23:21

2-May-20 23:21

If you are referring to array cells with two dimension values then you should use a two-dimensional array. As it is you can pass any values in to NodeCoord but there is no way of telling if they are valid. So you could end up with lots of random memory corruption.

Calin Negru2-May-20 23:35

2-May-20 23:35

Thanks Richard
How do I declare a two (or more) dimensional array? The problem is I might need arrays with a great number of dimensions. I need a `one fits all` type of solution.

modified 3-May-20 5:42am.

Richard MacCutchan2-May-20 23:48

2-May-20 23:48

Just like a one-dimensional, but you declare the two dimensions. Think of it as a block of items having some number of rows and columns. so you could have something like:

C++

#define MAXROW 10
#define MAXCOL 5

ChartNode Chart[MAXROW][MAXCOL];
ChartNode NodeCoord(int row, int column)
{
    if (row > 0 && row < MAXROW &&        // make sure row index
        column > 0 && column < MAXCOL)    // and column index are within range
    {
        return Chart[row, column];  // return the cell
    }
    else
    {
        return NULL; // error
    }
}

All of these features are well documented in the C/C++ documentation and the various tutorials on the language.

Calin Negru3-May-20 0:00

3-May-20 0:00

the two dimensional array seems like something too good to be true Smile | :)

The compiler is definitely doing something suspicious behind the courtain.
Thanks.

modified 3-May-20 6:31am.

Richard MacCutchan3-May-20 0:07

3-May-20 0:07

I think you could do with studying all the features of C (or C++ if that is what you are using). Trying to learn a language by posting questions here will take ten times as long, and you will still miss most of it.

«_Superman_»9-May-20 20:01

«_Superman_»

9-May-20 20:01

Internally it's just continuous memory that is allocated for a 2 dimensional array (For any no. of dimensions for that matter).
The compiler uses the specified dimensions to calculate the offset into the memory to fetch.
For instance, offset of Chart[2][3] could be calculated as -

(sizeof(ChartNode) * MAXROW * 2) + (sizeof(ChartNode) * 3)

«_Superman_»
I love work. It gives me something to do between weekends.

Microsoft MVP (Visual C++) (October 2009 - September 2013)

Polymorphism in C

Calin Negru3-May-20 3:26

Property Sheet Display issues

3-May-20 3:26

Often I edit my posts/replies shortly after making them, I can`t organise myself in a single swing.

LegacyGuy30-Apr-20 9:27

LegacyGuy

30-Apr-20 9:27

I have a shipping piece of software, that uses property sheets for Tools/Options. For almost all my customers everything is perfect, but for just 2 or 3 the property sheets appear as though the dialog units are too large. The fonts, edit boxes, and all controls are about 1/3 too large, but with the same 0,0 origin. Even so, the containing dialog size is unchanged, so the result is that some of the controls on the right and bottom are either clipped or not visible at all.

We only use property sheets in two places, and for customers with this problem, both instances are affected identically. This only happens with Property sheets, and not with normal dialogs.

The resources are defined in the .rc file like:

DLG_PREF7 DIALOG  10, 91, 300, 179
STYLE DS_ABSALIGN | DS_SETFONT | DS_MODALFRAME | DS_3DLOOK | DS_CENTER | WS_POPUP | WS_CAPTION | WS_SYSMENU
CAPTION "Font"
FONT 8, "MS Sans Serif"
BEGIN
    LTEXT           "Fixed-width font",79,7,7,119,12,SS_CENTERIMAGE
    COMBOBOX        80,131,7,126,300,CBS_DROPDOWNLIST | CBS_SORT | WS_VSCROLL | WS_GROUP | WS_TABSTOP
    LTEXT           "Proportional font",87,7,25,119,12,SS_CENTERIMAGE
    COMBOBOX        88,131,25,126,300,CBS_DROPDOWNLIST | CBS_SORT | WS_VSCROLL | WS_GROUP | WS_TABSTOP
    LTEXT           "Font size",-1,7,43,119,12,SS_CENTERIMAGE
    EDITTEXT        705,131,43,20,12,ES_RIGHT | ES_NUMBER | WS_GROUP | WS_TABSTOP 
END

A picture would be worth a thousand words, but I can't post a picture. Imagine if you could have used ctrl/mouse-wheel to increase the size of the contents of just this dialog.

I am stumped. Does anyone have an idea of what might be happening?

Re: Property Sheet Display issues

Victor Nijegorodov30-Apr-20 10:01

Victor Nijegorodov

30-Apr-20 10:01

It seems to be a one of the property pages displayed in the property sheet.
How do other pages look like (I mean in the resources)?

Re: Property Sheet Display issues

Richard MacCutchan30-Apr-20 21:33

30-Apr-20 21:33

I have run your dialog and tried various changes to see if it affects it but nothing seems to go wrong. It may be worth checking the versions of Windows that the clients are running to see if that is a common factor.

Strange chars

_Flaviu28-Apr-20 8:31

_Flaviu

28-Apr-20 8:31

I am trying to convert a C Linux library to Windows. And I've met something weird. I have a variable:

C++

struct dir_struct
	{
		void* display;
		char directory[DIR_NAME_LEN];
...
....

but when I listed this variable on my debugger:

C++

TRACE("\n=>%s\n", dir_struct->directory);

Result:

=>/Wise Registry Cleaner/Oe©*BºcE«Mò×¦£š{@Q—Y|†Š˜b!//„]Û¡¼à<br />
k3©‘ø¼/´4þ"Ðõ÷düJ¤$èû8©KªõÝ5ø³/ò|"Áæpç5V—{?///î¢¸1Ðq$\ß=*C±ì///¶//ˆòíÔ¤ö]¨m´'ÈˆÊÉ<IJ©LMq¶,(òúDlXx2¦ÂGrÌ<br />
*õ;øœÎj¬þ‹.Ý‚Ä/AÆ]GÝ¨	ïk<br />
‚¥¡C©…º/GÏ/^×ÒÇ\b/`£ç£×9Å‰_9ßÛ8}añˆg–¿§<êZøM[ÈCø`ƒ"ö~J÷L4/Lè¶Î¸G¢Êèojµ¶/–ãÛxÌZÀ##qÇ¸=//Yâ¢	¶LÉKºëÈš"Êã!"Ìd#vŽM-Gþ}?<br />
H’ƒÿidÔ’£lÖ#S///Híz<nÉ(BîU’{t0////i&e.ÆF|S.`[íbd6Óôà…ŸÝÂw+{[0//ÈÎû,ðŠ$Èí7ƒr«¨/,"–ZHfã	w<br />
f¡//ãúàÛ»lô4u1ävj/üØœˆ?‰¦(Qñ^Å/<br />
'	†SZPÔoärEÁ/@«Ô<br />
³$,©ÀÙ‚ø//í*‚Þ!ÍÙÉ4ÅZw6(bÚxZž†"ŠÊl…¡Ã//Ö¢HÄ£:vÄ,)‰²/UˆÂÔU±´Íüêp//Ÿ°ÖÏe¢ªHÝXaÍ///mÐw1	ç²ª6r*n//r šT3fÞ:cùÇz<br />
/€à1UK_îˆ]Xj//ôÁ½ÓR¦ÍO?)Ë>Ø£á€MÃ=¿U"œ*CÜFeR//ˆ¹5»mŠ€€†Â#øD/×c|ÔÂq,’X`t¸I//TÁ ½w¢u,¸	ß÷ìÔ¶‚Ô„;%ÀÔI¯¤w¡"lïÌC8ñÅÿ/ùê‡ŒmŸ‹àúÚÃÓÍ3ãµ+TG¯@qÜ¾A¬t´+vÛutô|‰Ä~:žÞHÏê6'9B~o½/þŒ#ƒ-©¶Ô"÷³'£//"Ù³{R"DLUÇ²]	œ<br />
1½&{ÙòMÇ–_o™ºEí /ôež…°Û¬"¢ ¿‚yÚÊ£Cýñ:(×N±/’z¹>eV®//§þ,÷‹ËÀòTÀÃS////////»&<br />
Þ¦)ûªÝvlleŽ/xØB¡RÚ_Ò^6y¿w`žs¤‘øÂÂO{;ªqûN/0€È#@–ñyøq½nç//Ëä8íþ»¡R5½ÐºˆÍ////////////<br />

Why I have this garbage ? Because my folder is Wise Registry Cleaner only ... If I would understand it, maybe I can get rid of it ...

Richard Andrew x6428-Apr-20 9:19

Richard Andrew x64

28-Apr-20 9:19

It's showing all that garbage because the character array is obviously not NULL terminated.

You'll have to look at the documentation to see how to know the proper length of the string.

The difficult we do right away...
...the impossible takes slightly longer.

_Flaviu28-Apr-20 9:40

_Flaviu

28-Apr-20 9:40

Thank you. I have seek it \0 char in that string, but I didn't found it ...

Richard Andrew x6428-Apr-20 9:57

Richard Andrew x64

28-Apr-20 9:57

There might be some other way that the library determines the length of the string. Is there any documentation?

Otherwise you can try adding this line of code before printing the string:

C++

dir_struct->directory[DIR_NAME_LEN - 1] = 0;   <<======================This line of code

TRACE("\n=>%s\n", dir_struct->directory);

The difficult we do right away...
...the impossible takes slightly longer.

Richard MacCutchan28-Apr-20 21:32

28-Apr-20 21:32

What is the complete definition of the dir_struct structure? In Linux the information provided by the readdir(3) - Linux manual page[^] system call provides a properly null terminated string.

_Flaviu28-Apr-20 21:54

_Flaviu

28-Apr-20 21:54

So in my case (in Windows) I am not getting that null on ending string (\0) ?

kalberts28-Apr-20 22:41

kalberts

28-Apr-20 22:41

How do you obtain the file name from Windows? Which API function call are you using? If the documentation for that API function call specifies that the name is null terminated, then you should not be getting the garbage. But some old file systems set off a fixed length buffer for the file name - even in Unix! The original Unix directory was 16 bytes per entry: two bytes inode, 14 chars filename. The orginal FAT had room for 8 char file name, 3 char extension. If the field was filled with a maximum length file name (in either Unix or FAT), there was no room for a terminating nul. If you reach the end of the field before finding a null, it is nevertheless the end of the field!

Remember that nul terminated strings is an idea conceived for the C language. It directoy conflicts with the ISO character set standard, whether ISO 646, 8859 or other variants. Other languages have used other solutions, e.g. in Pascal, a string is (at least in most implementations) represented by a length field associated with the string buffer (so the ISO NUL character can be used in the ISO standard way!). Many other languages to the same.

DOS was developed before C and Unix. Windows was developed before Unix had become very important, at least in the market segments Windows was aimed at. So you should not take for granted that all sorts of C / Unix conventions have been adopeted in every other segment.

Richard MacCutchan28-Apr-20 22:47