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Sure, if you posted the data back to the main thread through for instance a user-defined windows message.
I do this sort of thing a lot in for instance socket programming, like pressing the "Connect" button of a chat program. Without having a separate thread, the whole program could freeze up for several seconds as the socket attempted to connect, since it's a blocking call.
KR
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The main thread would have to be waiting on a synchronisation object, a message queue or event in order to respond to the child threads signal. You can't preemptively interrupt any thread except to suspend it, resume it or terminate it.
Nothing is exactly what it seems but everything with seems can be unpicked.
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Well, I was thinking of using this method to hook the main thread to the event:
Native C++ Event Handling
However, hooking to an event doesn't imply that your main thread can no longer do anything but wait for the event, which led to my above question.
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I don't know if this would work. I suspect the event function would get called on the child thread or a temporary thread rather than on the main thread.
Although Microsoft labels all this up as 'Native' you'll notice the bracketed [event_source(native)] attributes indicating managed extensions. I guess this probably works like the COM event system where the child thread will get temporarily suspended when it raises the event and then the rutime will actually scrape up (probably from a pool ) a separate system thread to call the event handler on, releasing the child thread to go its merry way after the hand off of any parameters. You could do this in straight C++ but being able to hand off any set of parameters is, I suspect, what's going to require the compiler magic indicated by [event_source(native)]. It's going to have to write some code for you based on the definition of the event class 
Personally I would use a straight forward Event object and have the main thread poll (WaitForSingleObject with a short timeout) for it periodically.
Nothing is exactly what it seems but everything with seems can be unpicked.
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That's something I could consider, but what if you were to wait for it periodically and do work from the main thread in between these periods? If the event were to be signaled while you aren't waiting, you'd miss it, right (in that case, everything would go haywire)?
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No the event would remain set and then the next time you waited for it the wait would succeed. The only way it would fail is if the client thread destroyed the event object on exit. That would be bad. It's not necessary though as the Event has to be shared with the main thread in order for this to work so the main thread can handle clean up. 
Nothing is exactly what it seems but everything with seems can be unpicked.
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I create a none-block socket to connect to another,someone would tell me why the connect function would aways return FALSE?
And how should I do such equal thing?
Thanks.
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connect() does not return a boolean. It returns an int.
A return value of 0 indicates success. A return value of SOCKET_ERROR indicates an error.
For a non-blocking socket, if you get a return value SOCKET_ERROR, you should check if the error
is WSAEWOULDBLOCK (using WSAGetLastError(). WSAEWOULDBLOCK means the connect hasn't completed yet
so you won't know if there's an error until you receive a completion notification/event.
Mark
"Posting a VB.NET question in the C++ forum will end in tears." Chris Maunder
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Hi all,
I have the following problem, I include the following header files:
#include <sql.h>
#include <sqlext.h>
But I receive this error:
[C++ Error] sqltypes.h(123): E2146 Need an identifier to declare
@ line 123 : typedef unsigned long ULONG;
Can anyone help me ??
Many Thanks
Regards,
The only programmers that are better than C programmers are those who code in 1's and 0's..... 
Programm3r
My Blog: ^_^
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Suggest you do a Google search on "E2146 Need an identifier". It appears to have something to do with the definition of winsock.h vs winsock2.h
hope this helps you.
John P.
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jparken wrote: It appears to have something to do with the definition of winsock.h vs winsock2.h
When why am I receiving the error in my sqltypes.h file ??
Google result:
Results 1 - 10 of about 59 for E2146 Need an identifier.
jparken wrote: hope this helps you.
Thanks
Regards,
The only programmers that are better than C programmers are those who code in 1's and 0's.....
Programm3r
My Blog: ^_^
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Looking through those headers I can't see why you'd get that message.
Do you have WIN32 defined (probably in the project settings preprocessor defines)? You should
Also, maybe try including windows.h before those includes, but I can't readily see where that
would make a difference.
Mark
"Posting a VB.NET question in the C++ forum will end in tears." Chris Maunder
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But you're using header files from the Windows Platform SDK, right? Or does Borland have
their own version of Windows headers?
"Posting a VB.NET question in the C++ forum will end in tears." Chris Maunder
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That's a library not a header 
Take a look through sqltypes.h - does it refer to "WIN32"? What about "HWND"?
"Posting a VB.NET question in the C++ forum will end in tears." Chris Maunder
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Yes, all of the header files are there.
sql.h
sql_1.h
sqlext.h
sqltypes.h
....
....
And all of the states "Microsoft Corporation" at to the top.
The only programmers that are better than C programmers are those who code in 1's and 0's.....
Programm3r
My Blog: ^_^
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Mark Salsbery wrote: Take a look through sqltypes.h - does it refer to "WIN32"? What about "HWND"?
"Posting a VB.NET question in the C++ forum will end in tears." Chris Maunder
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How can I determine what type of media is associated with a letter in Windows?
Example:
A: is floppy,
B: not used,
C: fixed drive,
D: CD-ROM,
etc.
In VC++ 6 please.
36. When you surround an army, leave an outlet free.
...
Do not press a desperate foe too hard.
SUN-TZU - Art of War
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Take a look at GetDriveType().
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Thank you, very much!
36. When you surround an army, leave an outlet free.
...
Do not press a desperate foe too hard.
SUN-TZU - Art of War
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hello everybody
i used to do quite a lot of vc a few years
but got a job using another programing lauguage called PReS. (I bet nobody has heard of it)
is vc still the language to learn or would vb.net or c# or somthing else be better
which the most used language these days
jooooe 
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Jooooe wrote: is vc still the language to learn...
If you need to.
Jooooe wrote: which the most used language these days
How could anyone possibly know the answer to this? 
"A good athlete is the result of a good and worthy opponent." - David Crow
"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne
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If you ask in here you know you're going to get the answer VC++ 
After all you're not a soft headed newbie who need his memory managed for him are you? Seriously it all depends on what you want to do, how much control you want over how it's done and how quickly you want it done.
Nothing is exactly what it seems but everything with seems can be unpicked.
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Jooooe wrote: which the most used language these days
www.tiobe.com keeps statistics on programming language search engine queries. As Mr. Crow stated, it is unlikely that this will be an accurate representation of what is used most as nobody could possibly know that, but it gives one a picture of how often a person resorts to a search engine query for a particluar language.
One could argue since MSDN is so thorough, that there will be fewer queries from users using Microsoft compilers which would indicate the statistics are probably less than accurate. One could also argue that the statistics merely indicate which languages require secondary assistance to get things done and could simply indicate a flawed help system for the leading compilers of that language.
Beware of buzzword fluctuations as they usually reflect the initial surge of queries to find out what a buzzword technology is. Those tend to taper off after the first year for newer technologies.
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