C / C++ / MFC Discussion Boards

piul3-Jan-11 0:14

3-Jan-11 0:14

Hi there!

I need an array of strings of char * type and I am not clear about how to free up memory after use. The code below does not work.

char * ptr_p_c[3];
ptr_p_c[0] = new char;
strcpy (ptr_p_c[0], "hi there");
ptr_p_c[1] = new char;
strcpy (ptr_p_c[1], "whatever");

delete ptr_p_c;

I know I shouldn't be using this type for strings and all this. Believe me, I've tried repeatedly to convince my customer this is not the right way to do things, but unfortunately it is not my decission...

Thanks a lot.

Re: array of char*

bleedingfingers3-Jan-11 0:30

bleedingfingers

3-Jan-11 0:30

First up, the "customer" has no business wrt such low level programming details. I smell something else here.

Anyway, to the point, the allocation itself is flawed. You are allocating just one character and copying several characters into it. A lot of corrupted memory. The delete will cry.

The proper way to delete is to loop through the array and delete every allocated sub array.

...byte till it megahertz...

my donation to web rubbish

Re: array of char*

piul3-Jan-11 0:40

piul

3-Jan-11 0:40

Something like this??

const int num = 3;
char * ptr_p_c[num];
for (int i = 0; i<num; i++)
    ptr_p_c[i] = new char[20];

strcpy_s (ptr_p_c[0], 9, "hi there");
strcpy_s (ptr_p_c[1], 7, "change");

for (int i = 0; i<num; i++)
    delete ptr_p_c[i];

Re: array of char*

bleedingfingers3-Jan-11 0:56

bleedingfingers

3-Jan-11 0:56

better

const int N = ??
const char* names[N] = {"...", "...", ...}
char *arr[N];
for(n=0;n<N;n++)
 arr[n] = strdup(names[n]);
// other code
for(n=0;n<N;n++)
 free(arr[n]);

...byte till it megahertz...

my donation to web rubbish

Re: array of char*

CPallini3-Jan-11 0:50

CPallini

3-Jan-11 0:50

Well, you already know that avoiding std::string is just plain silly so I don't bother you more:

char * ptr_p_c[2];
ptr_p_c[0] = new char[sizeof("hi there")];
strcpy (ptr_p_c[0], "hi there");
ptr_p_c[1] = new char[sizeof("whatever")];
strcpy (ptr_p_c[1], "whatever");
delete ptr_p_c[0];
delete ptr_p_c[1];

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]

Re: array of char*

T21023-Jan-11 1:04

T2102

3-Jan-11 1:04

Agreed. Use std::string or you can use one of many already existing string classes. You also could create an array of char[] if you have a series of strings whose length the compiler can computebv in advance.

Re: array of char*

Alan Balkany5-Jan-11 4:15

Alan Balkany

5-Jan-11 4:15

It looks like your sample is an example of why std:::string should be used: The null terminator will overflow the char[] buffers you allocated by one byte.

Re: array of char*

CPallini5-Jan-11 7:24

CPallini

5-Jan-11 7:24

You're wrong.
Hint: I didn't use strlen.
Smile | :)

Re: array of char*

Alan Balkany5-Jan-11 8:38

Alan Balkany

5-Jan-11 8:38

Oops, I stand corrected.

Re: array of char*

David Crow3-Jan-11 3:12

David Crow

3-Jan-11 3:12

Does the memory for those strings necessarily need to come from the heap? If not, what about:

char *ptr_p_c[] = { "hi there", "whatever" };

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"Man who follows car will be exhausted." - Confucius

Re: array of char*

Maximilien3-Jan-11 4:32

Maximilien

3-Jan-11 4:32

piul wrote:
Believe me, I've tried repeatedly to convince my customer this is not the right way to do things, but unfortunately it is not my decission...

If you are a professional, then MAKE IT your decision.

if it takes less time to develop, less time to debug, make the code more secure and readable, than you need to do it the right way.

anyway,you should delete each item in the ptr_p_c array.

good luck.

Watched code never compiles.

Re: array of char*

Richard MacCutchan3-Jan-11 4:48

Richard MacCutchan

3-Jan-11 4:48

piul wrote:
Believe me, I've tried repeatedly to convince my customer this is not the right way to do things

Why does the customer need to know how you are implementing a small piece of code? If they understand that level of detail then why do they need you?

Just say 'NO' to evaluated arguments for diadic functions! Ash

Re: array of char*

CPallini3-Jan-11 9:39

CPallini

3-Jan-11 9:39

Because he's afraid of using new for instancing strings.
Roll eyes | :rolleyes:

Re: array of char*

«_Superman_»3-Jan-11 6:07

«_Superman_»

3-Jan-11 6:07

I know dumb customers.
I also know dumber customers.
But this is the dumbest customer.

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

Microsoft MVP (Visual C++)

Polymorphism in C

Re: array of char*

CPallini3-Jan-11 10:01

CPallini

3-Jan-11 10:01

You know dumb customers.
I know dumb customers.
He knows dumb customers.
Hey Superman, your customers.
Hey Superman, YOUR customers
are just not that dumb.
Big Grin | :-D

Re: array of char*

bleedingfingers3-Jan-11 20:45

bleedingfingers

3-Jan-11 20:45

So dumb customers are your kryptonite, eh?

...byte till it megahertz...

my donation to web rubbish

Re: array of char*

«_Superman_»4-Jan-11 3:21

«_Superman_»

4-Jan-11 3:21

A good reason to dislike them. Smile | :)

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

Microsoft MVP (Visual C++)

Polymorphism in C

get a value from dialog box to dialog box?

mathivanaan2-Jan-11 23:16

mathivanaan

2-Jan-11 23:16

Hi,

I am using MFC with two dialog box. One dialog box have text box and submit button. once i type some text and submit this button, how to get values from another dialog box?

any sample pls share

Regards,
M.Mathivanan

Re: get a value from dialog box to dialog box?

Richard MacCutchan2-Jan-11 23:42

Richard MacCutchan

2-Jan-11 23:42

If they are both modal dialogs then you need to run the first dialog, save the data after it completes, then run the seond and use the values from the first as required.

Or did I misunderstand your question?

Just say 'NO' to evaluated arguments for diadic functions! Ash

Re: get a value from dialog box to dialog box?

Nuri Ismail2-Jan-11 23:47

Nuri Ismail

2-Jan-11 23:47

I'm not sure if I correctly understand the question but I suppose you have some problems with dialog data exchange (DDX) architecture. If this is the case check out this[^] and this[^] MSDN pages.

Also have a look at this[^] example. I believe it can be useful for you. Smile | :)

Re: get a value from dialog box to dialog box?

CPallini3-Jan-11 0:29

CPallini

3-Jan-11 0:29

There's a nice article written by toxcct, here at CodeProject: Dialogs Communication[^].
Smile | :)

Re: get a value from dialog box to dialog box?

David Crow3-Jan-11 3:17

David Crow

3-Jan-11 3:17

Are the dialog boxes "peers" or "subordinates?" It's much the same either way, but it might help to clarify your question if you provided such details.

Shadow around the dialog

john56322-Jan-11 21:16

john5632

2-Jan-11 21:16

Hi,

I need to draw shadow aroung the rounded dialog, How can I do that?

Re: Shadow around the dialog

Nuri Ismail2-Jan-11 22:40

Nuri Ismail

2-Jan-11 22:40

First, have a look at this[^] article.

Another option is using CS_DROPSHADOW class but it requires a Windows version >= XP.

And finally, check out this[^] article.

Choose the most appropriate approach for you. Smile | :)

VC++

Gokulnath0072-Jan-11 19:50

Gokulnath007

2-Jan-11 19:50

To Get the Current UserName and HostName in vc++ mfc

char host[200];
gethostname(host,201);
CString str,user;
str=host;
TCHAR acUserName[100];
DWORD nUserName = sizeof(acUserName);
GetUserName(acUserName, &nUserName);
user=acUserName;

Regards,
N.GokulNath

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