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How to control two threads accessing same variable
in MFC
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Use a critical section[^] to protect the access. On the other hand, if your variable is a standard type (int, char, bool, ...) you don't need to protect it because writing or reading it is an atomic operation.
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I believe 16 and 32 bit integer writes are atomic on x86 ONLY if they are aligned.
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Forgive me for being slightly cynical, but if I have an 32 bit integer that's not aligned on a 32 bit boundary an x86 won't read it in one fell swoop. And if you're doing an update to a variable you generally need to lock it somehow to get the correct memory barriers inserted into your code.
Cheers,
Ash
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with a lot of attention.
Use synchronization mechanisms like mutex, critical sections, .... especially when trying to write the variable.
Watched code never compiles.
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...and equally especially when trying to read the variable. 
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hello, everyone.
"the attempt to edit the code in cimageDoc::OnSegManual in file--- imagedoc.cpp failed" POPS UP, when mapping menu item to function in MFC classWizard. And The files are writable.
How can I mend the problem?
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I have simple template method in my class. I think it is self-explaining:
template<class T> T* GetCell(int row,int col)
{
return ((T*)GridCellGet(col,row,0,0,RUNTIME_CLASS(T)));
}
It works in debug build (MFC DLL), but it does not compile in release (static) build. It seems RUNTIME_CLASS() has different definition for DLL and static builds. Error message is:
error C2039: 'classT' : is not a member of ....<br />
It teems preprocessor replaces RUNTIME_CLASS(T) with 'T' instead of type name, I guess it has higher priority. Do you have idea how to solve this?
Thank you.
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Use #ifdef __DEBUG__ to compile differently in debug and release?
> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Computers don't kill programs, users kill programs <
> "It doesn't work, fix it" does not qualify as a bug report. <
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Goto declaration of RUNTIME_CLASS macro in afx.h and you will see something like
#define _RUNTIME_CLASS(class_name) ((CRuntimeClass*)(&class_name::class##class_name))
#ifdef _AFXDLL
#define RUNTIME_CLASS(class_name) (class_name::GetThisClass())
#else
#define RUNTIME_CLASS(class_name) _RUNTIME_CLASS(class_name)
#endif
If you have _AFXDLL defined in your project replace RUNTIME_CLASS(T) with T::GetThisClass()
Otherwise you will have a problem. The macro will expand to &T::classT which will fail, and you will need some other construct.
Edit: This might work (NOT tested)
template<class T> T* GetCell(int row,int col)
{
return ((T*)GridCellGet(col,row,0,0,T().GetRuntimeClass()));
}
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Thank you, it works, but I think it always creates temporary object so it will be bit inefficient but maybe it won't be noticeable problem.
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Ok. If performance is critical, you could solve this by having a class variable (static T temp) to use to avoid the constructor each time. Who knows, that construct might even win you some kind of most-akward-contruct-of-the-year award.
<edit>Ah forget about that and just cache the return value of T().GetRuntimeClass().
</edit>
It's a bit fishy that you had different behavior in debug and release. You might want to check what defines you have in release vs debug. If _AFXDLL is defined in debug it should be defined in release as well. Notice that it's implicitly defined when defining some other symbols like _AFXEXT (and what else)
home
modified on Tuesday, June 15, 2010 9:22 AM
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hai
This started happening when I added a malloc and free. I checked in Debug it is while freeing the memory.
I tried the runtime lib settings.It was initally /MDd that time this error _CrtIsValidHeapPointer was coming.Then I tried to changed to /MTd then it in call stack shm_test.exe1_unlock_fhandle( ) was there.
chikach
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What exactly is the error?
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I m getting CrtIsValidHeapPointer debug assertion
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There is a discussion of this assert here[^], but it basically means that somewhere in your code between malloc() and free() your memory pointer has been corrupted. Try stepping through your code with the debugger to see if you can spot where this is happening.
It's time for a new signature.
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I need to learn C because I am about to develop microcontroller projects that use C. I got books about C.
I might need C++ in the future, but for totally different things.
Is it possible to use stdio.h in MS Visual C++?
How do I do so?
How do I keep command prompt applications from closing the console after they are done playing? If i want to see my "hello world" or some variable number output.
Is Keil uVision the only compiler to suit ARM microcontrollers?
Maybe I need something like Borland compiler so I can write ARM code and PC code on the same compiler?
Thank you.
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have you tried:
#include "stdio.h"
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yes i did
it doesn't add the header
gives out an error message before i run my hello world program
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So what is the error message?
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Just tells me that there are errors during compilation.
and displyas a built-in hello world example result
(when you choose that you want to build c++ console it already writes a c++ hello world program using iostream.h)
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Those error messages are telling you what's wrong.
If you want help, you must tell us what the error messages say.
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no
maybe i should switch to a different compiler
visual studio professional is very big
too big for my computer
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