C / C++ / MFC

27-Jan-08 21:06

rp_suman wrote:
Probably you forget to increment value of "i" before return like i = i + 1;.

Yes I forgot. Sorry! Poke tongue | ;-P

rp_suman wrote:
Why you are having char* argument as you are returning char*?

To return the original address for later use. As:

char* Test(char* str)
{
  static int i = 1;
  sprintf(str, "%d.", i++); // Now I remember to increment it.
  return str;
}
// ...
char sBuf[10] = {0};
int v = 0;
for( ; v < 3; v++) {
  printf(Test(sBuf));
  printf("\n");
}

Maxwell Chen

Re: C++

rp_suman27-Jan-08 21:12

rp_suman

27-Jan-08 21:12

Maxwell Chen wrote:
To return the original address for later use.

That's nice..

Thanks & Regards,
Suman Big Grin | :-D

Working with two classes

CodingLover27-Jan-08 17:03

27-Jan-08 17:03

Hi all,

I have a class and one of it has a function as follows.

void CMsgRecorder::SetGroupState(char chState) // Eranga
{
// do the processing
}

defining as follows,

class CMsgRecorder
{
public:
void SetGroupState(char chState);
}

Other class has following function.

void CRfSvrDriver::ShowInfo()
{
//call SetGroupState() from here
}

It's also define as public function in CRfSvrDriver class. How can I call SetGroupState() from the ShowInfo() which are in two classes.

Help really appreciate Smile | :)

I appreciate your help all the time...
Eranga Smile | :)

Nitheesh George27-Jan-08 17:12

27-Jan-08 17:12

use inheritance.

class CMsgRecorder
{
public:
void SetGroupState(char chState)
{
do-something;
}
};

class CRfSvrDriver : public CMsgRecorder
{
public:
void ShowInfo()
{
SetGroupState();//calls the base function CMsgRecorder::SetGroupState
}
};

CodingLover27-Jan-08 17:20

27-Jan-08 17:20

Yes I do, but the question is this. I already use one class there as follows.

class CRfSvrDriver :
	public CCmdDriver

How can I used another class, how to separate those two

I appreciate your help all the time...
Eranga Smile | :)

Nitheesh George27-Jan-08 17:37

27-Jan-08 17:37

then why don't you try this

class CRfSvrDriver :public CCmdDriver,public MsgRecorder

OR

u want to maintain two separate version of the class CRfSvrDriver ?

CodingLover27-Jan-08 17:41

27-Jan-08 17:41

Ok, I can separate by a comma and do it. But then I comes with a constructor issue. I can't change my constructor now.

So I change my plan, simply used a pointer to the other class as follows. Include the CMsgRecorder header file in the ShowInfo header file.

void CRfSvrDriver::ShowInfo(CMsgRecorder* msgRec)
{
msgRec->SetGroupState('R');
}

But it gives a compile error.

error LNK2019: unresolved external symbol "public: void __thiscall CMsgRecorder::SetGroupState(char)" 
(?SetGroupState@CMsgRecorder@@QAEXD@Z) referenced in function "public: int __thiscall 
CRfSvrDriver::ProcessCommand(class ATL::CStringT<char,class strtraitmfc_dll<char,class="" atl::chtraitscrt<char=""> > 
>,unsigned int,class CMsgRecorder *)" 
(?ProcessCommand@CRfSvrDriver@@QAEHV?$CStringT@DV?$StrTraitMFC_DLL@DV?$
ChTraitsCRT@D@ATL@@@@@ATL@@IPAVCMsgRecorder@@@Z)
</char,class>

I hope it is linker error, but all functions are declared correctly. You have any suggestion for me on this.

I appreciate your help all the time...
Eranga Smile | :)

Nitheesh George27-Jan-08 18:00

27-Jan-08 18:00

the linker cannot find the definition of SetGroupState that is the problem. whether u declared SetGroupState as a static function? or not defined it.

And another thing i don't think the method u opted is a good programming practice. Inheritance is the good method in such situations.

CodingLover27-Jan-08 18:06

27-Jan-08 18:06

Ok pal. Thanks.

Actually I missed one thing there. Those two classes are in two projects. I think that is why there is a linker error. What I can do now. Frown | :(

I appreciate your help all the time...
Eranga Smile | :)

Nitheesh George27-Jan-08 18:17

27-Jan-08 18:17

Then make a DLL of the project that contains class CMsgRecorder. Then include .h file of the class and lib file in your new project. Then compile it. ie's it.

CodingLover27-Jan-08 18:48

27-Jan-08 18:48

I'll see, because working with DLLs are really new work for me. Frown | :(

I appreciate your help all the time...
Eranga Smile | :)

exception from C function?

sheshidar27-Jan-08 17:42

sheshidar

27-Jan-08 17:42

class CMsgRecorder
{
public:
void SetGroupState(char chState)
{
do-something;
}
};
Now you can use multi-one inheritance like this
class CRfSvrDriver : public CMsgRecorder,public CCmdDriver
{
public:
void ShowInfo()
{
SetGroupState();//calls the base function CMsgRecorder::SetGroupState
}
};

George_George27-Jan-08 16:11

27-Jan-08 16:11

Hello everyone,

As far as I know, C function does not throw exception.

But Bjarne said in his book, section 14.8 Exception and Efficiency,

--------------------
In particular, an implementation knows that only a few standard C library functions (such as atexit() and qsort()) can throw exceptions, and it can take advantage of that fact to generate better code.
--------------------

What did he mean? C function could really throw exception? What exception -- C++ exception or structured exception?

thanks in advance,
George

Maxwell Chen27-Jan-08 18:13

27-Jan-08 18:13

Why don't you read the next paragraph?!

Maxwell Chen

George_George27-Jan-08 18:23

27-Jan-08 18:23

I read all the section, Maxwell!

Could you show your point to my original question please?

regards,
George

Maxwell Chen27-Jan-08 18:57

27-Jan-08 18:57

"... it might have been converted ..."

Maxwell Chen

George_George27-Jan-08 19:10

27-Jan-08 19:10

Hi Maxwell,

The whole sentence is "it might have been converted to use the C++ operator new". How could C code use C++ operator new?

regards,
George

Maxwell Chen27-Jan-08 19:27

27-Jan-08 19:27

Remember that the scope now is in C++. Stroustrup's book is a C++ book. And "C Library" is a subset of C++. Even though the function names of C Runtime Library are the same, the internal may be different.

Maxwell Chen

George_George27-Jan-08 19:34

27-Jan-08 19:34

Thanks Maxwell,

I have got your point.

regards,
George

new invokes VirtualAlloc

George_George27-Jan-08 15:59