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If I remember my finer points of the C++ spec right, extern and const are at odds - a global variable that is declared const automatically gets internal linkage (that is, it needs to be defined in the same translation unit (CPP file) as the declaration). When the compiler gets to another CPP file, it knows there's a constant called whatever but it does not know its value. Adding extern doesn't change the variable's linkage because the compiler still doesn't know the value of whatever. It's similar to templates, where the entire template class has to be visible to all CPP files.
You should be able to put const int whatever = 76; in the header file, and there won't be any symbol collisions because each CPP file will have its own whatever with internal linkage.
--Mike--
"Adventure. Excitement. A Jedi craves not these things."
-- Silent Bob
1ClickPicGrabber - Grab & organize pictures from your favorite web pages, with 1 click!
My really out-of-date homepage
Sonork-100.19012 Acid_Helm
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Michael Dunn wrote:
You should be able to put const int whatever = 76; in the header file, and there won't be any symbol collisions because each CPP file will have its own whatever with internal linkage.
Sure, but it will also have all of those constants stored in each translation unit, won't it? Considering I'm not just storing a single constant int, it's a lot of overhead that I'd like to avoid.
Anyways, it turns out that once I included header.h in source.cpp, everything became fine and dandy again. It seems to need to see that the constants are marked as extern before it allows other translation units (some) to see them.
It probably makes sense. I just can't see it right now. 
J
May the bear never have cause to eat you.
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Jamie Hale wrote:
Sure, but it will also have all of those constants stored in each translation unit, won't it?
I'm not a guru on the details of optimization, but I think in release modes, the optimizer should put the value 76 right into the compiled code, instead of referencing a variable, so you won't have multiple variables (one per CPP file).
--Mike--
"Adventure. Excitement. A Jedi craves not these things."
-- Silent Bob
1ClickPicGrabber - Grab & organize pictures from your favorite web pages, with 1 click!
My really out-of-date homepage
Sonork-100.19012 Acid_Helm
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Hi,
Can anyone please tell me how to hide the cursor from blinking in a rich edit control? I made it read only, since I don't want users to enter anything, but they can still select stuff, and the cursor is there when they click anywhere inside it. Both of these I don't want.
I tried using HideCaret() but it's not working for me. Am I doing something wrong here?
I basically want it to look and behave like a static control but want the formatting capabilities of a rich edit control. Hmm, if nothing works out I may have to dig the RTF specs and do things on my own, which I don't want.
Thanks to anyone who helps me out.
Regards,
Rohit Sinha
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Hi, I would like to store some pictures in memory in their raw format. What is the best way to do this memory wise? Should I use "new" or "malloc" or some built in windows function. The largest file will probably be no larger 500k - 1MB. Should I allocate individual chunks or one large chunk that will fit them all and just keep pointers to the their positions? Should I do anything else?
Thanks,
Clint
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new and malloc are identical internally. and, they're both fine for the sizes you're talking about. if you start getting into utterly huge images, like 50MB or so, you might want to consider VirtualAlloc and friends.
clintsinger wrote:
Should I allocate individual chunks or one large chunk that will fit them all and just keep pointers to the their positions?
i always alloc them individually, under the assumption that the heap manager can do a better job of allocating and paging memory than i can do it myself.
i write a lot of image processing apps, and i've never had a problem with new/malloc (or LocalAlloc) for images in the 500-1000K range (or even in the 10-20MB range).
-c
There's one easy way to prove the effectiveness of 'letting the market decide' when it comes to environmental protection. It's spelt 'S-U-V'.
--Holgate, from Plastic
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I am a very beginner in MFC programming. Right now I have to find a way to load and display an bitmap image and get the RGB values for each pixel into an array. But I have no clue what classes and methods to use. Could anybody give me some instructions on this? Any help is appreciated.
Thanks very much!
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Check out Chris Maunder's DIBSection wrapper. A DIBSection is an image which provides you with a pointer to the byte array containing the image information. If you can use GDI+, even better. My C# image processing articles convert very easily to C++, which will give you what you want. I've written a number of articles on GDI+ in C++ as well.
There are no MFC classes to help you. ::LoadImage is an API call you can use to load a bitmap from disk, otherwise, it's GDI+ or third party classes.
Christian
No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002
Hey, at least Logo had, at it's inception, a mechanical turtle. VB has always lacked even that... - Shog9 04-09-2002
Again, you can screw up a C/C++ program just as easily as a VB program. OK, maybe not as easily, but it's certainly doable. - Jamie Nordmeyer - 15-Nov-2002
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Arrrrgh.
I jumped through the appropriate hoops to change my application to use MFC in a static library. And then, silly me, I tried to change it back.
181 link errors like this:
nafxcwd.lib(thrdcore.obj) : error LNK2005: "public: virtual void __thiscall CWinThread::Delete(void)" (?Delete@CWinThread@@UAEXXZ) already defined in mfc42d.lib(MFC42D.DLL)
I've compared my project settings to other applications and I can't see any difference.
What am I missing?
The project is set to use MFC in a shared DLL. The C runtime is Multithreaded DLL. _AFXDLL is defined. As is _MCBS (or whatever).
J
May the bear never have cause to eat you.
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The linker is pulling in both the static version of MFC (nafx*.lib) and the import LIB (mfc42d.lib). So double-check your preprocesor settings, and do a rebuild-all.
--Mike--
"Adventure. Excitement. A Jedi craves not these things."
-- Silent Bob
1ClickPicGrabber - Grab & organize pictures from your favorite web pages, with 1 click!
My really out-of-date homepage
Sonork-100.19012 Acid_Helm
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Actually, I think it has to do with the order in which the libraries are getting linked/searched.
Here[^]'s what I found about it.
I fiddled with it for a bit, got fed up, and blew away my project files. Started from scratch, and now everything's back to the way it was.
J
May the bear never have cause to eat you.
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I am looking for a good book on WinSock programming that uses MFC. Any suggestions?
-- Steve
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VC++ MFC Extensions by Example by John E. Swanke has an example of MFC's CSocket.
I highly recommend that you design an implement Windows socket applications using Win32 Winsocket. I recommend Network Programming for Microsoft Windows, Second Edition by Anthony Jones and Jim Ohmund.
Kuphryn
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Still having problems finding a book. I bought a great book that covered everything and when I got home, I realized the book uses C#, not C++ (I don't have a C# compiler, besides, all my applications are in C++). Are there any good books for Network Programming that use C++ functions?
-- Steve
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Hi,
I'm creating a small application that will function as a filter-application on a mailserver (as an extension lib). The case:
I receive an email from the server, as 'raw data'. I need to extract all attachments attached in that file.
Anybody has a clue how to do this? I actually don't want to write sourcecode that parses the message and looks for every single supported encoding-type .. I couldn't find any support for it in the MSDN library (but I only spend a few minutes searching)
Help appreciated 
--
Alex Marbus
www.marbus.net
But then again, I could be wrong.
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It looks very promising, but I really can't afford the 600 bucks 
--
Alex Marbus
www.marbus.net
But then again, I could be wrong.
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I'm afraid you will have to write your own code for this, unless you decide to use something which is already out there. MAPI, while OK for client side stuff, won't scale well in a server environment. You won't have to take care of too many suported encoding types, just understand MIME. Go to http://www.imc.org/rfcs.html#mime[^] for more information on MIME. Don't let the number of RFCs there scare you away, it's not for the faint of heart anyway (  ).
Although I'm sure you could find a lot of open source stuff out there to help you get started.
AlexMarbus wrote:
The case:
I receive an email from the server, as 'raw data'.
Wait a minute now. Are you saying the mail server will mail you the emails that it gets so that you can then extract the attachments and do your stuff with it? This can be horribly slow, and can bog the server down. Imagine what it'd be like, the same email travelling on the network twice. Or did I get it wrong and you meant something else? In any case, my suggestion would be to install your dll as a proxy for the server. It can then process the emails before they get to the email server itself, and will have done its processing (stripping the attachments, scanning for virii, whatever). Let the filter and the server communicate via the computer memory, don't use files or the network for it. You can't imagine how slow it will make everything if it's a busy site.
Regards,
Rohit Sinha
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Rohit Sinha wrote:
I'm afraid you will have to write your own code for this, unless you decide to use something which is already out there.
I did: http://www.funduc.com/decenc.htm It does exactly what I need
Rohit Sinha wrote:
In any case, my suggestion would be to install your dll as a proxy for the server.
That is exactly what it is: a filter application for a certain mailserver (ArgoSoft). See http://triplef.marbus.net for more details.
Thanks for your reply
--
Alex Marbus
www.marbus.net
But then again, I could be wrong.
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My program works fine under Windows 98, but crashes under Windows XP.
Is it MFC problem?
A debug version works fine though, only release version crashes when i open a file.
Is anything I should check or add to make it work under Win XP.
Thanks
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As a rule, you need to provide more detail when you post questions. What statement does it crash on? Does it always crash in the same place?
Given that the debug version 'works fine' but the release version does not, I would guess that you have one or more uninitialized variables. Under debug, things tend to get set to a known state (usually zero) for you. Under release, that doesn't happen, and you get whatever garbage was in the variable when it was created or allocated. The reason things work under Win98 but don't under WinXP is that WinXP does a better job of validating parameters and such. You are getting away with this under Win98 simply because it's not checking something that WinXP does.
Software Zen: delete this;
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Thank you, Gary.
At least I know now that I should check everything in my program now and it is not MFC's fault.
You gave me a clue. The crash happens when I open and close a file several times.
I wish I could send a code which causes it, but I still didn't find it.
Ok, thank you again.
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hi,
Could somebody please give me pointers to some sample code
for printing a JPEG image ?
thanx,
Deepa
Deepa
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