C / C++ / MFC

25-May-04 4:48

Hi geeks,

Please tell me when to use a MACRO and when to use an INLINE FUNCTION in C++. If this question has been asked before, please point me to that link.

I need an answer comparing the two. Please dont post definitions of macro and inline function as i am aware of them. Please give the answer in terms of efficiency, speed, code-size, pre-compilation/post-compilation, and things like that.
And please give examples ... Rose | [Rose]

...Avenger

Remember... testing & debugging are always part of programming ...so exterminate those stinking bugs

Maximilien25-May-04 4:53

25-May-04 4:53

always use inline ( or ordinary methods ).

the only reason I can give is that macros are preprocessor stuff and are not "debuggable"

Maximilien Lincourt
Your Head A Splode - Strong Bad

David Crow25-May-04 5:48

David Crow

25-May-04 5:48

Maximilien wrote:
the only reason I can give is that macros ... are not "debuggable"

That should be reason enough. Very few things should exist as a preprocessor macro. The ability to type-check parameters is a must.

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

Curi0us_George25-May-04 6:32

Curi0us_George

25-May-04 6:32

My general rule is that if it can be done as an inline function, it should be.

There are some things which cannot be done with an inline function, but can be done with a macro. Those are rare, though.

Gary R. Wheeler25-May-04 15:04

Gary R. Wheeler

25-May-04 15:04

avenger_sb25 wrote:
Hi geeks,

That's a wee bit rude, don't you think?

avenger_sb25 wrote:
I need an answer comparing the two. Please dont post definitions of macro and inline function as i am aware of them. Please give the answer in terms of efficiency, speed, code-size, pre-compilation/post-compilation, and things like that.
And please give examples ...

This sounds suspiciously like you've got a take-home exam in a programming course, and you're looking for us 'geeks' to provide the answers.

I'll give you the answer to your question. My rate is $75USD/hr (you're getting the student discount, BTW), 4 hours minimum, in advance, in cash.

Software Zen: delete this;

avenger_sb2525-May-04 17:48

25-May-04 17:48

Is that something you say when you dont know the answer Mr?

Anyway a proper answer would have been appreciated. I was asked this questionj at a job interview. When i will get the job, i will pay u. LOL

...Avenger

Remember... testing & debugging are always part of programming ...so exterminate those stinking bugs

size of an empty class??

avenger_sb2525-May-04 4:41

25-May-04 4:41

Hi einstines,

i was asked this question at an interview:

class a<br />
{<br />
};<br />
main()<br />
{<br />
cout<<sizeof(a);  //WHATS THE OUTPUT?<br />
}

I can obviously run the program to find the output but i need an explanation about the output.

PLEASE ANSWER: WHAT IS THE OUTPUT????

...Avenger

Remember... testing & debugging are always part of programming ...so exterminate those stinking bugs

jmkhael25-May-04 4:53

jmkhael

25-May-04 4:53

i did just that in VC++

class A
{
};

int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
int i = sizeof(A);
cout << "Sizeof A:" << i << endl;
}

it displayed 1.

I switched to assebmly listing and the linker has generated the following code:

77: int i = sizeof(A);
004018AB mov dword ptr [i],1 <----- Notice here, the linker knew its an empty class and automatically replaced its size by 1
78:
79: cout << "Sizeof A:" << i << endl;
004018B2 mov esi,esp
004018B4 mov edx,dword ptr [__imp_?endl@std@@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@1@AAV21@@Z
004018BA push edx
004018BB mov edi,esp
004018BD mov eax,dword ptr [i]
004018C0 push eax
004018C1 mov ebx,esp
004018C3 push offset string "Sizeof A:" (004130d4)
004018C8 mov ecx,dword ptr [MSVCP60D_NULL_THUNK_DATA (00415234)]
004018CE push ecx
004018CF call dword ptr [__imp_??6std@@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@0@AAV10@PBD@Z (004
004018D5 add esp,8
004018D8 cmp ebx,esp
004018DA call _chkesp (004014bc)
004018DF mov ecx,eax
004018E1 call dword ptr [__imp_??6?$basic_ostream@DU?$char_traits@D@std@@@std@@QAEAAV01@H@Z (0041523c)
004018E7 cmp edi,esp
004018E9 call _chkesp (004014bc)
004018EE mov ecx,eax
004018F0 call dword ptr [__imp_??6?$basic_ostream@DU?$char_traits@D@std@@@std@@QAEAAV01@P6AAAV01@AAV01
004018F6 cmp esi,esp
004018F8 call _chkesp (004014bc)

Papa

while (TRUE)
Papa.WillLove ( Bebe ) ;

avenger_sb2525-May-04 5:01

25-May-04 5:01

Ya, thanx for ur reply and to tell the technique to see linker output Wink | ;)

(thats a new thing i learnt)

But, why 1? is it property of the linker or a C++ standard to make size of an empty class as 1. Please tell.

...Avenger

Remember... testing & debugging are always part of programming ...so exterminate those stinking bugs

jmkhael25-May-04 5:10

jmkhael

25-May-04 5:10

Never tested it on unix, but one thing im sure of, is that empty structs are forbidden if you compile the file as a c file and not as a cpp.

However while permitting generation of an empty class, the linker is forced to allocate some space for it (vtable ...) and cos its empty, sizeof just returned the minimal size reserved for a class.

Papa

while (TRUE)
Papa.WillLove ( Bebe ) ;

Curi0us_George25-May-04 6:38

Curi0us_George

25-May-04 6:38

VTable is only allocated if the class actually contains virtual functions.

The size of an empty class will always be greater than zero because two objects must not occupy the same space. (As DavidCrow pointed out)

David Crow25-May-04 5:57

David Crow

25-May-04 5:57

avenger_sb25 wrote:
WHAT IS THE OUTPUT????

It won't be zero, as that would allow two different objects to have the same address. If sizeof(a) returned 0, then the following would be allowed:

main()
{
    a a1, a2;
    if (&a1 == &a2)
        ... // if we get here, the compiler is faulty
}

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

Nemanja Trifunovic25-May-04 6:01

Nemanja Trifunovic

25-May-04 6:01

From the Standard (1.8.5)

Unless it is a bitfield, a most derived object shell have a non-zero size and shell occupy one ore more bytes of storage. Base class sub-objects may have zero size.

avenger_sb2525-May-04 17:46

25-May-04 17:46

Base class sub-objects may have zero size

Can u please give a working example. I did

class p<br />
{<br />
};<br />
class q: public p<br />
{<br />
};<br />
p o1;<br />
q o2;<br />
	cout<<sizeof(o1);<br />
	cout<<sizeof(o2);

I get 1 in both. Thank you.

...Avenger

Remember... testing & debugging are always part of programming ...so exterminate those stinking bugs

menu next to images

Member 466743725-May-04 4:34

Member 4667437

25-May-04 4:34

how do i place a image next a menu

Clint

jmkhael25-May-04 4:43

jmkhael

25-May-04 4:43

What about this[^]

Papa

while (TRUE)
Papa.WillLove ( Bebe ) ;

Member 466743725-May-04 9:26

Member 4667437

25-May-04 9:26

thank you for your reply but, these examples are all part of the toolbar not nex to the toolbar.

Clint

Maximilien25-May-04 9:30

25-May-04 9:30

huh ?

what exactly do you want ? a popup/drop down menu in a toolbar ?

Maximilien Lincourt
Your Head A Splode - Strong Bad

Question about Saving Fonts.

Member 466743726-May-04 11:14

Member 4667437

26-May-04 11:14

something that looks like a standard menu ie File,edit,options but can have a large picture, on the left which may, or may not overlap the toolbar.

Clint

Mike Doner25-May-04 4:15

Mike Doner

25-May-04 4:15

I have a quick question regarding saving font settings in a drawing type package.

For example, an application like Corel Draw who has a TextBox on the canvas who uses Arial font, how would that information be saved?

Obviously, we'd store the text in some kind of string/char object, but for the font, would you just store the szFontName, nPointSize and some style bits (bold/italics/underline)?

We're working on an issue with our product where somebody has chose to save the LOGFONT structure, but we're finding that the logfont.height guy is based on the DC because of the call:

logfont.lfHeight = -MulDiv ( PointSize, GetDeviceCaps(hdc, LOGPIXELSY), 72 );

Bottom line, Whats the common way to save this stuff?

Any info you could send would be greatly appreciated.

Mike.

Re: Question about Saving Fonts.

Johan Rosengren25-May-04 21:28

Johan Rosengren

25-May-04 21:28

I would save the font height in typographical points - that is, PointSize rather than logfont.lfHeight above.

You might want to consider using CreatePointFontIndirect for font creation, then you can save/load the LOGFONT directly.

Help: How to retrieve UNIT of a scroll bar

fotoONE25-May-04 3:57

fotoONE

25-May-04 3:57

excerpted from MSN" The user scrolls the content of a window by clicking one of the arrow buttons, by clicking the area in the shaded shaft, or by dragging the scroll box. When the user clicks an arrow button, the application scrolls the content by one unit (typically a single line or column). "

Question: how to retrieve the size (by pixel) of a unit?

ZZH1234567@HOTMAIL.COM

Re: Help: How to retrieve UNIT of a scroll bar

Maximilien25-May-04 4:19

private member in base class problem

25-May-04 4:19

have a look at CScrollBar::GetScrollInfo and the SCROLLINFO struct.

also, depending on the application, it can be user/programmer defined, for example, if you need to scroll a bitmap, you can set the "unit" to 1 pixel, or if it's text, you can compute it to scroll the height of the next/previous line.

Maximilien Lincourt
Your Head A Splode - Strong Bad

kzyczynski25-May-04 3:52

kzyczynski

25-May-04 3:52

Hello
I'm writing a class derived from MFC's CTime with additional methods for my
app but have a problem.
Time variable in base class is declared as follows:
private:
time_t m_time;
Is there any 'magical c++' trick to access it in derived class? Smile | :)

(without changing base class of course)
For now i see only two options (not deriving):
Rewrite entire class
or put CTime in new class as a member and do some tricks with all required methods.

But maybe someone hava a better idea?
thanks
Chris

Re: private member in base class problem

Maximilien25-May-04 3:55