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Zac Howland wrote: basically does a memcpy
Not quite - the Standard says:
The implicitly defined copy constructor for class X performs a memberwise copy of its subobjects. The
order of copying is the same as the order of initialization of bases and members in a userdefined
constructor (see 12.6.2). Each subobject is copied in the manner appropriate to its type:
- if the subobject is of class type, the copy constructor for the class is used;
- if the subobject is an array, each element is copied, in the manner appropriate to the element type;
- if the subobject is of scalar type, the builtin assignment operator is used.
Virtual base class subobjects shall be copied only once by the implicitlydefined
copy constructor (see
12.6.2).
Personally, I only define copy constructor/assignment operator when I've got a member that's not RAII compliant...and then I think 'Why doesn't that sub-object manage itself' and change it so I can use the implicit copy-constructor and assignment operator!
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I said "basically" for a reason. Try fitting what the standard declares into a 1 sentence note about why you should declare (or not declare) a copy-constructor.
Stuart Dootson wrote: Personally, I only define copy constructor/assignment operator when I've got a member that's not RAII compliant...and then I think 'Why doesn't that sub-object manage itself' and change it so I can use the implicit copy-constructor and assignment operator!
I'm just the opposite. I almost always define them explicitly so that if I have problems, I already have the methods there for me to debug and see what is going on. You can't step through implicit functions.
If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week
Zac
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Sorry - what I should have said was that I didn't like the comparison of the copy constructor to memcpy - it copies each member individually, it doesn't just copy the raw bytes of the object. Which is why I'm quite happy to rely on implicit copy constructors - because 99% of the time, they're implementing what I'd be implementing anyway.
I take your point about having copy constructors to step through @ debug time - it's just not something I find myself doing.
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Stuart Dootson wrote: Sorry - what I should have said was that I didn't like the comparison of the copy constructor to memcpy - it copies each member individually, it doesn't just copy the raw bytes of the object. Which is why I'm quite happy to rely on implicit copy constructors - because 99% of the time, they're implementing what I'd be implementing anyway.
The main reason I compare it to memcpy is simply to emphasize that if you have a pointer member variable, only the pointer value will be copied (that is, a new object that the pointer is pointing to will not be created).
As a side note, they will only implement what you would do if your data members are simple types. If they are complex types that don't have a copy-constructor/assignment operator defined, chances are it isn't going to do what you would expect (e.g. if you have a custom vector-type class that doesn't have a copy-constructor).
Stuart Dootson wrote: I take your point about having copy constructors to step through @ debug time - it's just not something I find myself doing.
After finding myself trying to debug implicit functions several times, I got in the habit of making sure they were explicit. It only takes one time of spending a week trying to figure out why your code doesn't work (when it should) before you want to make sure you don't run into the problem again.
If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week
Zac
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i'm currently experiencing a strange problem under vc++ .NET 7.0. i hope
someone has a hint for me, i'm kind of lost atm.
i'm using a vector of object instances in my code.
using the release build,I get a runtime error intermittently while adding to the vector using push_back.
When i use the debug build. i can add
as much elements as i want without any problems .
Is there any special setting to be done for reease build?
It is is simple as
EMEventContainer instance("key","value");
this_vector.push_back(instance);
But it does not work properly in release build.
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rana74 wrote: Is there any special setting to be done for reease build?
No. You have a bug.
"Alot of the people on this forum are incredibly stupid, thinking that the internet is real"
Score: 1.0 in the Soap Box
led mike
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post copy constructor of EMEventContainer
dynamic allocations inside EMEventContainer?
Kuphryn
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This is usually a sign that you have some memory issues elsewhere in your code. Debug builds allocate extra space before and after sections of memory to help indicate if you have any buffer overrun issues. Release builds don't have that, so if you do have such a problem, you will corrupt memory rather quickly. Things to look for are the constructor of the EMEventContainer object, its copy constructor, its copy assignment operator, any heap allocations within that class, and if you are using multiple threads, any unprotected accesses to an STL container.
If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week
Zac
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Hello,
I have Visual C++ program that implements Graphical User Interface (GUI). This program uses CWinApp, CFormView, CFrameWnd, and CDocument.
Now I need to package this C++ application to work as COM DLL (or ActiveX).
This program must be used as popup window from another program written in Java.
Is it possible to convert Visual C++ program with GUI into COM DLL or ActiveX ?
Please advice.
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I expect you'll have to create a new MFC ActiveX project and copy across and/or modify the existing code.
Kevin
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My former employer wanted a similar thing done. After months of research, we found out that yes, we could reuse SOME of the existing code, but that we would still have to rewrite a lot of code to get it to behave as an ActiveX control. Basically, if your code is layered (e.g. a 3-layer setup where GUI is separate from business logic is seperate from data access) then you will likely only have to rewrite the GUI layer. If not, you will be doing it piece-meal.
If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week
Zac
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Hello,
Thank you for information!
I found an article called "Adding automation to MFC applications":
http://www.codeproject.com/com/mfc_autom.asp
This article outlines steps that should be taken to enable MFC application as COM object.
I am trying to follow these steps. But, I am running into number of problems. I am new to Visual C++ environment, and it takes me some time to resolve these issues.
The problem that I am trying to resolve now is with IDL file. I am able to compile IDL with MIDL. I included generated header file into my Visual C++ project. However, when I include generated C file, I am getting compile errors.
If at some point I will succeed with this project, I will share details of my work on this web site.
Thank you!
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I have the following code:
std::vector<emeventcontainer>::iterator it=pevent.begin();
try{
while(it != pevent.end()) {
RepDataManager::Log(RepDataManager::HIDEBUG, " Processing next");
EMEventContainer curr = *it;
......
.....
.....
...
it++;
RepDataManager::Log(RepDataManager::HIDEBUG , " About to process next element");
}
This function succeeds in debug builds but results in abnormal crashes in release build .I am using VC++ .NET 7.0
How can i avoid this crash?I have read abotu checked iterators but do not know how to work around this crash.I have tried #define _SECURE_SCL 0 but to no avail.
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rana74 wrote: EMEventContainer curr = *it;
By any chance , Should there any problem, in how curr is used.
Can you see, by commenting that usage, iteration though all elements is problem free?
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I have read that we can use
#define _HAS_ITERATOR_DEBUGGING 0
#define _SECURE_SCL 0
to disable the checked-iterator behaviour in VC++ 5.0
However,instead of defining this at the top of each c++ file,is there some place in project settings where i can define this ,so that it applies to all c++ files?
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1. Include your macros in a common header file and include this file in all your required files.
OR
2. Include your macros in stdafx.h
OR
3. If I am not wrong there is a compiler option "/D". Check this in MSDN.
S o h a i l K a d i w a l a
modified 21-Apr-21 21:01pm.
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Hi there.
I was coding a c++ dll using some tipical inheritance structure where classes classB and classC extended abstract classA.
From a MFC c++ dialog based application, everything works like a charm, but I need this stuff to be used from a VB applicaction.
So I started reading and reached that I should code COM objects, and more exactly, ATL.
First approach worked, and I'm able to call an object from the ATL dll in a VB test code.
However, problems are when I try to reproduce my inheritance structure within all these ATL interfaces mess.
This is the code i would like to run written in c++:
ClassA object = new ClassB();
As you can see, I declare object as ClassA, but I instantiate it as ClassB. I don't want classA to be able to be instantiated (abstract), but I can't declare an ATL interface over an abstract class, so, I won't be able to use it from VB. And I don't know how to deal with inheritance. Child classes don't seem to "see" parent public and protected methods when used in the VB test app.
I don't post any code cause I don't think it would help. If you know what am I talking about, I'm sure you'll be able to point me to the issue, maybe a good and clear article about all this stuff.
I've made some further reading, but with no success. At the point, not exactly stuck, but quite lost.
Any help would be greatly appreciated.
Thanks so much.
Palako
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Is your abstract class (ClassA) a pure abstract class, as in all of the methods are virtual?
If so, you are describing a classic COM style interface.
To say that a class cannot derive from an abstract class is not correct. You can derive from it, but of course, you must implement the methods that it would provide. A common way of doing this using ATL (which uses 'upside-down' inheritance) is to define an intermediate templated class, typically ClassAImpl<> which takes a class as it's template parameter. The impl class can then use something like
T* pT = static_cast<t*>(this)
to get at the concrete class's instance when necessary.
For more details, read this[^] article by Jim Beveridge, which explains the evolution of the ATL design.
Steve S
Developer for hire
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i want to block the e-mail attachment in internet explorer. whenever user attaches or trying to attach something with the mail it block the activity. i need the code to block the gmail attachment using VC++.
any one knows please reply thanks
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This question is asked here[^] ,too.
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Hi all.
I have a listview handle and some item index. I want to select it via windows api.
Can someone help me?
Thx in advance.
Best Regards,
Marco Alves.
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Set the item state to include LVIS_SELECTED.
If it's a single select, you might need to unset that bit for the current item.
Steve S
Developer for hire
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try SetCurSel(ItemNumber)
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That is for a list box, not a list view control
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