Call to a constructor while executing (obj < 3) . Kindly explain? - C / C++ / MFC Discussion Boards

Re: Add support for Memory leak detection

Hamid_RT11-Jun-09 21:32

Hamid_RT

11-Jun-09 21:32

See Visual Leak Detector [^].

Of one Essence is the human race
thus has Creation put the base
One Limb impacted is sufficient
For all Others to feel the Mace
(Saadi )

segmentation problem

sandeep_dhruwa11-Jun-09 19:31

sandeep_dhruwa

11-Jun-09 19:31

Help me with these program
/* program to illustrte read function with pointer */
//this program may not work properly because of memory problems in read
#include<stdlib.h>
#include<stdio.h>
#include<unistd.h>
#include<string.h>
int main()
{
char *buf,c;
int nread;
memset(buf,0,0);
buf=malloc(1024);
nread=read(0,&buf,100);
printf("characters read: %d\n",nread);

if(nread == -1)
{
write(2,"An error occured in read function\n",27);
}
else
{
if(nread==0)
write(2,"Data is not written to the filedescriptor\n",27);
else
write(1,&buf,nread);
}
free(buf);
}

output:
sandeep@sandeep Unsure | :~

$ ./a.out <x
characters read: 75
this is Kead program
which is throwing lots of errore
lets correct them
Segmentation fault

Re: segmentation problem

Cedric Moonen11-Jun-09 20:13

Cedric Moonen

11-Jun-09 20:13

sandeep_dhruwa wrote:
char *buf,c;
int nread;
memset(buf,0,0);
buf=malloc(1024);

You have to call malloc before calling memset. Otherwise, you will try to write into an invalid pointer.

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

Re: segmentation problem

sandeep_dhruwa11-Jun-09 21:06

sandeep_dhruwa

11-Jun-09 21:06

still I am getting the error

Re: segmentation problem

Cedric Moonen11-Jun-09 21:11

Cedric Moonen

11-Jun-09 21:11

And for the read and write functions, don't pass the address of your buffer variable: it is already a pointer. Pass the pointer directly:

read(...,buffer,...);

(apply that for every read and write).

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

Re: segmentation problem

sandeep_dhruwa11-Jun-09 23:51

sandeep_dhruwa

11-Jun-09 23:51

thanks it solved
thankyou

Re: segmentation problem

CPallini11-Jun-09 21:25

CPallini

11-Jun-09 21:25

sandeep_dhruwa wrote:
nread=read(0,&buf,100);

sandeep_dhruwa wrote:
write(1,&buf,nread);

You should use buf, not &buf.
For instance

nread = read(0, buf, 100);

BTW your code is a mess, you really need a good C tutorial.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Call to a constructor while executing (obj < 3) . Kindly explain?

Member 397434711-Jun-09 18:01

Member 3974347

11-Jun-09 18:01

class CA{
  private:
    int m_Var;
  public:
        CA(int x=0): m_Var(x){cout<<"1";}
        bool operator < (const CA &obj2) {     cout<<"2";       return (m_Var < obj2.m_Var) ? true : false;}
};
int main(void) {
  CA obj1=2;
  if(obj1 < 3){cout << "In If block" << endl;}
}

the output of this code is 112In If block .. i can understand the reason behind the first 1 and "2In If block" .. i dont understand when the second 1 is being called?

as per my understanding when (obj1<3) executes it may call obj1.operator<(3)

But constructor is being called but whats makes it to call?
kindly explain why the second 1 is being displayed?

Re: Call to a constructor while executing (obj < 3) . Kindly explain?

Naveen11-Jun-09 18:18

Naveen

11-Jun-09 18:18

Member 3974347 wrote:
as per my understanding when (obj1<3) executes it may call obj1.operator<(3)

Not actually. It is actually called like

obj1.operator<( CA(3));// A local temporary object is created here.

Here the integer 3 is automatically converted to a CA object by involking the constructor. Such conversions are called implicit conversions. You can prevent such conversions using the explicit keyword[^]

nave

[OpenedFileFinder] [My Blog]

Re: Call to a constructor while executing (obj < 3) . Kindly explain?

N a v a n e e t h11-Jun-09 18:23

N a v a n e e t h

11-Jun-09 18:23

You are so fast! Big Grin | :-D

Navaneeth

How to use google | Ask smart questions

Re: Call to a constructor while executing (obj < 3) . Kindly explain?

Naveen11-Jun-09 18:26

Naveen

11-Jun-09 18:26

Well, I borrowed some monkeys[^] from Rajesh. Big Grin | :-D

nave

[OpenedFileFinder] [My Blog]

Re: Call to a constructor while executing (obj < 3) . Kindly explain?

Member 397434711-Jun-09 18:28

Member 3974347

11-Jun-09 18:28

Thanks.

Re: Call to a constructor while executing (obj < 3) . Kindly explain?

N a v a n e e t h11-Jun-09 18:22

N a v a n e e t h

11-Jun-09 18:22

Member 3974347 wrote:
But constructor is being called but whats makes it to call?

Because constructor accepts a int.

Member 3974347 wrote:
as per my understanding when (obj1<3) executes it may call obj1.operator<(3)

Your operator overload accepts const CA & but you specified the expression obj1<3, since type CA has a constructor which takes int, a temporary will be created by passing 3 to the constructor of CA and this is the reason for the second time constructor call.

Use explicit keyword to avoid the confusion.

Smile | :)

Navaneeth

How to use google | Ask smart questions

Re: Call to a constructor while executing (obj < 3) . Kindly explain?

Member 397434711-Jun-09 18:38

Member 3974347

11-Jun-09 18:38

Thanks

need help on liked error

vigneshvdm11-Jun-09 16:50

vigneshvdm

11-Jun-09 16:50

in turbo c on executing the program i get linked error and undefined symbol even for predefined functions like rectangle line etc... even the example programs given encounter the same problem..
please help

vicky

Re: need help on liked error

CPallini11-Jun-09 21:36

CPallini

11-Jun-09 21:36

vigneshvdm wrote:
in turbo c on executing the program i get linked error and
undefined symbol even for predefined functions like rectangle line

These cannot happen when you execute your program. Can happen, however when you try to compile your sources.

vigneshvdm wrote:
undefined symbol

You probably forget to include graphics.h that is required to compile when using graphic functions and data structures.

vigneshvdm wrote:
i get linked error

You got linker error because you probably forget to link with graphics.lib.

See, for instance [^].
Smile | :)

How to get ip address of current socket

cozyu11-Jun-09 16:10

cozyu

11-Jun-09 16:10

Dear all,

I have two lan cards.
So I have two ip address, too.

When I connect to server, how to get ip address of connected socket (clinet side NOT server side).

I could get ip address list of desktop using 'gethostbyname()'
But I didn't figure what ip address is current ip(lan card)

Do you have any solution?

Thanks.
cozyu

Re: How to get ip address of current socket

yifanernei11-Jun-09 17:02

yifanernei

11-Jun-09 17:02

try getsockname() func

c programing project on rejistration

seiyfu yesuf11-Jun-09 12:04

seiyfu yesuf

11-Jun-09 12:04

Hi there how are u am fine and then to the point am a fresh student in some university and i have an assignment in modular c programing that work arijister of university the fuction must contain the student's nam, id number,nationality,father's name,occopation bed number.And am not any acces to do these am search many sits but am not get much for my problem pleas help me download the answer as you can and am went to say you do not worry about my grammer it is not my mother tounghthank you.

Re: c programing project on rejistration

molesworth11-Jun-09 12:13

molesworth

11-Jun-09 12:13

seiyfu yesuf wrote:
pleas help me download the answer

The answer to what? You haven't asked a question...

I'm assuming you haven't been given this project in the first week of your course, so you must have learned some programming before this. What have you done to make a start on it? What have you done in the way of system design? In programming?

There are three kinds of people in the world - those who can count and those who can't...

Re: c programing project on rejistration

Rajesh R Subramanian11-Jun-09 12:55

Rajesh R Subramanian

11-Jun-09 12:55

Do your assignment yourself.

It is a crappy thing, but it's life -^ Carlo Pallini

Re: c programing project on rejistration

chirag_chauhan11-Jun-09 18:00

chirag_chauhan

11-Jun-09 18:00

Try seraching for "C Tutorials" on Google, and look at some examples u will get an idea to start-up.

Reduce the noise in the program

Nikhil_777711-Jun-09 11:27

Nikhil_7777

11-Jun-09 11:27

Hi,

I managed to compile this audio recording code but the header is corrupt. I know this because I compared the header output from this program and a neat .wav file using HexEdit.

http://www.scribd.com/doc/16336997/CPP-Code

here is the code. I din't wanna put a 5 page code in this page. So uploaded to scribd.

I need to make changes to the header. Can anyone give me some direction?

Thanks

Niks

Re: Reduce the noise in the program

Nikhil_777711-Jun-09 11:28

Nikhil_7777

11-Jun-09 11:28

It is giving so much noise that the audio it is recording is very unclear.

Thanks

Re: Reduce the noise in the program

Michael Schubert12-Jun-09 0:00

Michael Schubert

12-Jun-09 0:00

I dared to click on the link and had a look at the code. Anyway, nobody is going to debug the code for you, you'll have to do it yourself.

Alternatively, you can have a look at the several articles on this site about sound recording.

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.