ATL / WTL / STL

Re: ATL and _pAtlModule-->Lock() failure.

4-Aug-06 9:11

I am just now learning COM with ATL, but will try to help.

_pAtlModule is a global variable declared in atlbase.h as:

__declspec(selectany) CAtlModule* _pAtlModule = NULL;

It is set in the constructor of "class ATL_NO_VTABLE CAtlModule : public _ATL_MODULE":

_pAtlModule = this;

So, if you have the normal ATL generated code in your main project file

class CMyATL_ProjectModule : public CAtlDllModuleT< CMyATL_ProjectModule ><br />
{<br />
public :<br />
	DECLARE_LIBID(LIBID_MyATL_ProjectLib)<br />
	DECLARE_REGISTRY_APPID_RESOURCEID(IDR_MYATL_PROJECT, "{157A51E9-ECF7-4D1B-8D66-694A7CEFB436}")<br />
};<br />
<br />
CMyATL_ProjectModule _AtlModule;

that global field will be set when you compile your program.

eXeonical..6-Aug-06 23:06

eXeonical..

6-Aug-06 23:06

> So, if you have the normal ATL generated code in your main project file

Well, no i dont. You see i dont have any need for an entire ATL project. What i need to do is to implement a single COM interface. So i hoped that i could just extend the CComObject class and have it done the easy way, instead of writing all the COM stuff myself.

This is what i came up with:
---------------------------------------------
class CSampleProsessorRoot : public CComObjectRoot, public ISampleGrabberCB
{
public:
HRESULT STDMETHODCALLTYPE SampleCB(double SampleTime, IMediaSample *pSample);
HRESULT STDMETHODCALLTYPE BufferCB(double SampleTime, BYTE *pBuffer, long BufferLen);

DECLARE_NOT_AGGREGATABLE(CSampleProsessorRoot)
BEGIN_COM_MAP(CSampleProsessorRoot)
COM_INTERFACE_ENTRY(ISampleGrabberCB)
END_COM_MAP()
};

typedef CComObject<CSampleProsessorRoot> CSampleProsessor;

Erase elements while iterating on a map

vikramlinux3-Aug-06 20:27

vikramlinux

3-Aug-06 20:27

Hi Friends,
Can I erase elements from stl map while iterating throught it?

Vikram S

Re: Erase elements while iterating on a map

Zac Howland4-Aug-06 3:40

Re: Erase elements while iterating on a map

4-Aug-06 3:40

The short answer is no. Erasing elements invalidates any iterators. If you don't need to do anything with the elements in the map prior to deleting them, use the version of erase that takes a range. If you do need to do something with them (say, call delete on each element first), I would create a function that would take a reference to the object (which would be a pointer in this case), and call delete in that function. Then use for_each on the map to delete each element and use the ranged erase method to clear the map.

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

Michael Dunn4-Aug-06 14:06

Michael Dunn

4-Aug-06 14:06

From the VC7.1 docs on map:

Inserting elements invalidates no iterators, and removing elements invalidates only those iterators that had specifically pointed at the removed elements.

--Mike--
Visual C++ MVP Cool | :cool:

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ATL application using activeX

CheerioMaster3-Aug-06 2:22

CheerioMaster

3-Aug-06 2:22

Hi!

Can anyone pls help me with this problem. I need to test my activex control in a very simple atl application. So I would really appreciate it if anyone here could be so kind to post code that I can use to test the control in ATL.

I basically just needs to be able to call one of the controls methods and write the returning value out to console for example!!

Thank you in advance!

Re: ATL application using activeX

Rob Caldecott3-Aug-06 3:34

Rob Caldecott

3-Aug-06 3:34

Can't you use the MS ActiveX Test Container application (tstcon32.exe) that ships with Visual Studio? Check in the Microsoft Visual Studio Common7\Tools folder.

Re: ATL application using activeX

CheerioMaster3-Aug-06 3:58

CheerioMaster

3-Aug-06 3:58

Thx for your time!

I know the control is working in the test container AND in MFC applications, but it has been reported that it doesnt work properly in ATL applications, which I find strange. Therefore I wanted to create a simple atl project and see if could reproduce the problem or not!

Thanks

Validity of CWndClassInfo content

xLobo231-Jul-06 0:27

xLobo2

31-Jul-06 0:27

Hi,

I've encountered decent issue with validity of CWndClassInfo structure of ATL's CWindowImpl. Suppose following scenario:

1. There is a control class derived from ATL's CWindowImpl and rich edit (available via RichEdit20.dll)
2. This control is instantiated - RichEdit20.dll is loaded, CWndClassInfo gets initialized (this time only, as a static content of our class), control gets created
3. Control is destroyed and the dll gets unloaded.
4. Control is instantiated again - dll gets loaded again, to different base address this time. No reinitialization of CWndClassInfo occurs, as it is static and 'valid' from last time.
5. Application crashes as it tries to use rich edit's window procedure (through CWndClassInfo, containing outdated information)

I 'solved' this by clearing m_atom member of CWndClassInfo explicitely; in such case CWndClassInfo gets reinitialized in #4. My knowledge of ATL is fairly limited, but I don't expect this to be correct solution, of course.

Where is the problem here? Should I invalidate the CWndClassInfo in some 'standard way'? Or should the dll not get unloaded at all?

Thx. for any hints D'Oh! | :doh:

Should I learn ATL/COM now?

CPP_Student30-Jul-06 14:59

30-Jul-06 14:59

Howdy! I have been learning C++ and windows programming with MFC since I got canned from my mainframe job last year. I had bought the COM and ATL 3.0 book years ago, and decided to read it a few weeks ago. However, I get to chapter 9 and see that the stuff covered has been redesigned with ATL 7.0. There is only one book out there written since 3.0 that covers 8.0. I have VS pro 2005, so I could continue to learn ATL 8.

But I am unsure if it is worth it for me to learn ATL/COM now, or if I should dive into C# and .NET, which I know nothing about, but have just bought some books on for .NET 2.0. Does the lack of books on the "older" technologies, like MFC, ATL, and COM mean that they are perhaps only supported by legacy systems, and potential employers would be more likely to want .NET experience?

What to do?

Thanks.

CPP_Student30-Jul-06 15:47

30-Jul-06 15:47

I should add that I have been learning DirectX, and writing a 3D modeler in C++/MFC, and was thinking of learning ATL/COM to separate the loading of models from various file formats, and support a plug-in capability (though I know nothing about this).

Re: Should I learn ATL/COM now? [modified]

Kevin McFarlane31-Jul-06 6:12

Kevin McFarlane

31-Jul-06 6:12

Probably not worth making the effort to learn ATL/COM now.

CPP_Student wrote:
Does the lack of books on the "older" technologies, like MFC, ATL, and COM mean that they are perhaps only supported by legacy systems

Pretty much - unless you're writing e.g., the next version of MS Office or something!

CPP_Student wrote:
and potential employers would be more likely to want .NET experience?

Yes.

Put it this way, whether or not you should learn ATL/COM you'll definitely need to learn .NET as well. So at the least you would have to learn both. My guess is that while you will continue to see requirements for C++ and even ATL/COM in the Windows world it will be increasingly combined with a requirement for .NET.

Kevin

CPP_Student31-Jul-06 7:52

31-Jul-06 7:52

That makes sense! Thank you. Cool | :cool:

I just want to be sure I learn something really well rather than a bunch of things a little bit. But, every job offering lists a different set of requirements. So, I want to concentrate on the harder ones (like .NET) and learn the easier stuff (like SOAP and many other accronyms) on the job.

-- modified at 13:55 Monday 31st July, 2006

Zac Howland31-Jul-06 8:32

31-Jul-06 8:32

CPP_Student wrote:
Howdy! I have been learning C++ and windows programming with MFC since I got canned from my mainframe job last year. I had bought the COM and ATL 3.0 book years ago, and decided to read it a few weeks ago. However, I get to chapter 9 and see that the stuff covered has been redesigned with ATL 7.0. There is only one book out there written since 3.0 that covers 8.0. I have VS pro 2005, so I could continue to learn ATL 8.

I would at least finish reading the ATL 3.0 book first. The reason is simple: in many of the new books, they refer to "this has been changed from version 3.0 ... and this is why." If you have at least a mild understanding of the way things were, you will gain and understanding of why they changed it and what may have to be changed in systems that are upgrading their libraries. From experience, that is a popular interview question.

CPP_Student wrote:
But I am unsure if it is worth it for me to learn ATL/COM now, or if I should dive into C# and .NET, which I know nothing about, but have just bought some books on for .NET 2.0. Does the lack of books on the "older" technologies, like MFC, ATL, and COM mean that they are perhaps only supported by legacy systems, and potential employers would be more likely to want .NET experience?

Don't let the mass flooding of the bookshelves at Barnes and Noble with all the books on .Net convince you that MFC, ATL, COM, STL, etc are out of date. As it stands right now, .Net is a very small segment of the programming jobs available (and for the most part, among the lowest paying positions as well). If you understand the fundamentals, you won't have any problems answering interview questions dealing with general programming nor .Net specific stuff (though, generally it is a bad idea for interviewers to ask language/library specific questions in the interview ... it is, and should be, expected that the applicant will have a learning curve to get up to speed with what a firm is doing). COM is especially important since it is one of the foundation technologies for .Net (.Net does a very nice job of hiding that from you).

CPP_Student wrote:
I should add that I have been learning DirectX, and writing a 3D modeler in C++/MFC, and was thinking of learning ATL/COM to separate the loading of models from various file formats, and support a plug-in capability (though I know nothing about this).

If you are looking to apply for a gaming company or a company that does a lot of modelling/simulation, you will want to understand COM, but the biggest part of your studies should be on solid C/C++ programming and mathematics. As for plugins, you don't need COM to create a plugin architecture (though, I have written a couple articles on here that describe how you can do so).

I assume you are looking to add some new skillsets to your portfolio while you are job searching. With that in mind, I will answer your question with a series of questions:

1) What type of job would you like to land (realistically)?
2) What areas do you think that job most likely be using (STL? COM? MFC? ANSI C?)?
3) How strong are you in those areas?

With answers to those questions, you can figure out which areas you should focus on.

By the way, if you are a strong C/C++ programmer, you should be able to pick up C# (and even Java) with only a week or 2 as your learning curve.

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

Kevin McFarlane31-Jul-06 9:11

Kevin McFarlane

31-Jul-06 9:11

Zac Howland wrote:
Don't let the mass flooding of the bookshelves at Barnes and Noble with all the books on .Net convince you that MFC, ATL, COM, STL, etc are out of date.

They're not quite out-of-date but IMO if they're all you can offer it won't be enough to keep you in work. That's certainly been my experience as a contractor.

Zac Howland wrote:
.Net is a very small segment of the programming jobs available (and for the most part, among the lowest paying positions as well).

Well, in the Windows world at least this is not the case.

Zac Howland wrote:
COM is especially important since it is one of the foundation technologies for .Net (.Net does a very nice job of hiding that from you).

Maybe so but you won't need to know it for 99% of interviews.

Zac Howland wrote:
By the way, if you are a strong C/C++ programmer, you should be able to pick up C# (and even Java) with only a week or 2 as your learning curve.

Well, it needs a bit more than that. The main learning-curve is the .NET framework. Moreover, even if it does take you only a few weeks to be comfortable you somehow have to convince employers that you've got a year or two's commercial experience just to get a look-in. It shouldn't be this way but that's life.

Kevin

Zac Howland31-Jul-06 9:24

Re: What I am trying to do [modified]

31-Jul-06 9:24

Kevin McFarlane wrote:
They're not quite out-of-date but IMO if they're all you can offer it won't be enough to keep you in work. That's certainly been my experience as a contractor.

As a contractor, things are a bit different. You are expected to come in and not have a learning curve. This is mainly because companies generally farm out the work that their people could do, but their attention is focused on higher priority (e.g. more difficult matters, or ones that require much more domain knowledge).

When you are looking to be an employee, things are not so strict. Companies don't expect you to know everything when you come in; they expect that you will be able to learn quickly. With a solid foundation in C/C++ and the common libraries (STL and MFC in particular), 95% of companies will call you back for second and third interviews.

I can tell you from experience that because of my strong C++ background, when I was job searching, I had offers coming in from companies begging me to do .Net programming. The learning curve is not very high when you know C++ and are trying to go to any other language.

Kevin McFarlane wrote:
Well, in the Windows world at least this is not the case.

A huge percentage of programming postions don't even touch Windows. Even those that do, the majority of them still deal with C/C++. Keep in mind ... the second largest consumer software producer is EA. 85% of their code (non-script code that is) is written in C/C++ and has nothing to do with .Net.

Kevin McFarlane wrote:
Maybe so but you won't need to know it for 99% of interviews.

If you are just looking to answer interview questions in hopes that they won't ask you anything dealing with the word "how", then you are correct.

Kevin McFarlane wrote:
Well, it needs a bit more than that. The main learning-curve is the .NET framework. Moreover, even if it does take you only a few weeks to be comfortable you somehow have to convince employers that you've got a year or two's commercial experience just to get a look-in. It shouldn't be this way but that's life.

Again, this is the case if you are an independent contractor. It is not the case when you are applying for a position within the company.

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

CPP_Student31-Jul-06 10:33

Re: What I am trying to do

31-Jul-06 10:33

Thanks for the replies! Until I got canned I was a mainframe TPF IBM assembler programmer who had spent 12 years applying my trade to online credit card authorization processing at Visa. Before that I worked for two airlines over 4 years. It is a very niche business app as well as language and OS. The airlines are the only ones hiring now, but I would have to move to Denver, India, or China. My family is here, and I live in Silicon Valley. So, I want to stay, and see the job market as complex, with each job posting listing a different set of accronyms WTF | :WTF:

So, having already studied C++ and MFC, and a little VB .NET (BORING!), I decided to learn DirectX, because it interests me. I decided to build a 3D modeling program, instead of writing a game, becasue it would enable me to learn C++ better, MFC, Win32, and basic Windows concepts.

Recently, I wondered if it would be a good idea to learn COM/ATL, and I could put the functions that load .x files into it. But then I encountered the dilemna I posted about here.

I figure that getting a new job using languages I have no commercial experience with would be easier if I have an actual application to show. So, that is why I am looking to expand my understand of the different tools out there, and I see COM in some job postings that also mention C++ and MFC.

Basically I feel like I am floundering at times. OMG | :OMG:

I was hoping that eventually there will be a need for .Net or C++ programmers that know DirectX, which is why I am wondering now about whether I should do COM or go to .NET. Every job posting wants people who have a deep knowledge of one or two languages and list of tools (those accronyms and programming platforms).

The hardest part in any programming job is learning the business application, not the programming language(s). I decided long ago (when learning VB .NET put me to sleep) that I need an application that is more complicated (and interesting) than the usual internet business model. So I ignore any job posting that wants SQL knowledge or the building of an internet/intranet app.

I don't want to end up in another niche like the one I just came from. I became one of the top experts of online credit card authorization processing, and I enjoyed it when I had something to work on, but the politics of working for a larger company that is owned and run by bankers who are so far removed from the work we do that they make incredibly stupid decisions, along with the inner politics of my area that included major cronyism, killed my work ethic. I actually wanted to get laid off so I could get a severance, which would enable me to retool. And I did get exactly that.

I am 43 and looking to make a new start. But I have a strong aptitude for programming and solving business problems. So, management is out (for now anyway). I also wonder about the usefulness of learning from books, since NONE use actual business solutions as part of the teaching.

I am hoping that the need for 3D programmers will increase in applications other than just games, as the hardware gets better and Microsoft improves its support with managed DirectX and Vista's better support of it.

-- modified at 16:36 Monday 31st July, 2006

Zac Howland31-Jul-06 10:57

31-Jul-06 10:57

CPP_Student wrote:
Basically I feel like I am floundering at times. I was hoping that eventually there will be a need for .Net or C++ programmers that know DirectX

While this may change a bit if Microsoft actually gets Vista out the door, managed code (VB.Net, C#.Net, and Managed C++) are not optimal for DirectX programming. It is good to understand COM because DirectX makes heavy use of it, and it is the foundation of the entire .Net library system, but in most cases, you won't find a need to create your own COM components.

CPP_Student wrote:
but the politics of working for a larger company that is owned and run by bankers who are so far removed from the work we do that they make incredibly stupid decisions, along with the inner politics of my area that included major cronyism, killed my work ethic.

I feel your pain there. The place I use to work for was just like that ... only it was run by marketing "gurus" instead of bankers ... same end result (aka stupid decisions on things they had no business trying to decide anyway).

CPP_Student wrote:
I am hoping that the need for 3D programmers will increase in applications other than just games, as the hardware gets better and Microsoft improves its support with managed DirectX and Vista's better support of it.

When Vista comes out, that may help you a bit. If you aren't too opposed to it, you may find that several government contractors dealing with Modelling and Simulation are constantly looking for graphics programmers (both DirectX and OpenGL). There aren't many in Silicon Valley, but if you look more towards southern CA, I know of a couple few that are almost always looking (Lockheed Martin, Raytheon, Alion to name a few).

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