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C++ needs to be able to create pointers to arbitrary objects for inheritance.
You could create a class OBJECT that is a base class that you derive from.
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The answer to your question is in the link provided by markkuk.
You can actually store a one byte character in an empty class.
class test
{
};
void main()
{
test test1;
*((char*)&test1) = 'A';
}
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Dangerous!
The standard says tat distinct objects must have distinct identity (and if the identity is the address, a common way to get that is posing sizeof(A) = 1 by definition).
But this is ... compiler dependent. (they can even use 4 bytes to preserve the alignment!)
An Empty B inheriting the empty A may still have sizeof(B) == 1, not 2.
2 bugs found.
> recompile ...
65534 bugs found.
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Why is it dangerous (maybe I didn't get you)?
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]
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Because what Santosh is trying to do is assign a char to a byte that it is not granted to really exist.
(it may or not depending on the compiler implementation and level of optimization)
2 bugs found.
> recompile ...
65534 bugs found.
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I'm almost sure you're right (I cannot see other ways to implement it, but this is a problem of mine).
Thank you.
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]
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Dear,
empty class does not have any size.
but size of operator always return +ve value.
so you get empty class size 1.
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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.
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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.
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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];
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better
const int N = ??
const char* names[N] = {"...", "...", ...}
char *arr[N];
for(n=0;n<N;n++)
arr[n] = strdup(names[n]);
for(n=0;n<N;n++)
free(arr[n]);
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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]
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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.
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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.
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You're wrong.
Hint: I didn't use strlen.
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]
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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
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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.
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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
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Because he's afraid of using new for instancing strings.
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]
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I know dumb customers.
I also know dumber customers.
But this is the dumbest customer.
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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.
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]
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So dumb customers are your kryptonite, eh?
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A good reason to dislike them.
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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
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