C / C++ / MFC

1-Apr-09 3:31

Member 476468 wrote:
Does anyone know how to solve this?

Solve what? Confused | :confused:

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Re: tapi

Member 4764681-Apr-09 6:47

Member 476468

1-Apr-09 6:47

In Visual Studio 2008, what replaces tapi.h?

Re: tapi

David Crow1-Apr-09 7:15

Multiple Inheritance question

1-Apr-09 7:15

Have you looked in the two include folders to see if the file exists, or search the .h files to see if they contain TAPI-related functions?

ForNow31-Mar-09 6:41

31-Mar-09 6:41

Hi,

I have derived class which has 2 base calsses CSyncObject and CSingleLock

Since the input to the CSingeLock is a pointer to a CSyncObject my question is

if I first create the CSyncObject can I reference that object object when executing

the Constructer for the CSingleLock with the "this" pointer

e.g. class mylock() : public CSyncObject(NULL) , public CSingeLock(this->

my question really is am I going down the right path

I would assume the "this" pointer gets initialized after excuting the first

contructer

Stuart Dootson31-Mar-09 7:10

31-Mar-09 7:10

ForNow wrote:
I would assume the "this" pointer gets initialized after excuting the first contructer

No, you should be OK - this code does 'the right thing':

#include <iostream>

class A
{
public:
   A(int x) { x_ = x; }
   int x_;
};

class B
{
public:
   B(A* a) { std::cout << a->x_ << std::endl; }
};

class C : public A, public B
{
public:
	C(int y) : A(y), B(static_cast<A*>(this)) {}
};

int main(int, char**)
{
   C c(33);
}

VC++ (unlike gcc) does raise a warning[^] about doing this, but reading the warning description, I don't think it applies in this case.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

ForNow31-Mar-09 16:24

31-Mar-09 16:24

It worked

Please explain what is the value of "this" pointer on entrance to B from my undertanding static_cast<a*> is just a cast

????

Stuart Dootson31-Mar-09 20:23

Re: Multiple Inheritance question code worked

31-Mar-09 20:23

ForNow wrote:
from my undertanding static_cast<a*> is just a cast

Not in the presence of multiple inheritance - with multiple inheritance, you have two bases whose members you have to contain in your object. That means that for (say) class C : public class A, public class B, you have this layout in memory:

+---------------+
|   A members   |
+---------------+
|   B members   |
+---------------+
|   C members   |
+---------------+

So, to cast a C* to a B*, you will have an offset, equal to the size of A's members.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

ForNow31-Mar-09 18:11

31-Mar-09 18:11

Hi,

class mylock : public CSyncObject, public CSingleLock
{
public:
mylock(BOOL bInitialLock);
BOOL Unlock();
};

mylock :: mylock(BOOL bInitialLock) : CSyncObject(NULL), CSingleLock(static_cast<CSyncObject*>(this), bInitialLock)

{
bInitialLock = FALSE;
}

Made a breakpoint when I tried to instatiate mylock with following code mylock my_threadlock(init_s);

at mylock the this value was 1feb8 as I steped into CsyncObject it remained 1feb8 when I got to CsingleLock's

contructer this value was bumped to 1FEC0 However m_hObject value was 1FEB8 CsyncObject value

Still have some debugging to do but thankx

this article also elucidates the point you tried to make

http://carcino.gen.nz/tech/cpp/multiple_inheritance_this.php

thankx again

Joe Woodbury31-Mar-09 8:11

Joe Woodbury

31-Mar-09 8:11

I disagree with Stuart. The "this" pointer should rarely be used in an initializer list. This is especially apt here since CSyncObject has virtual classes and the virtual table hasn't been set up at this point.

I also think your class is a mistake and misunderstands CSyncObject() and CSingleLock(). The point is that there is one synchronization object with multiple threads locking that object. That locking is done by instantiated CSingleLock() at the start of a scope and upon exit of that scope, CSingleLock will be destructed regardless regardless of how the scope was exited.

Moreover, with your code, what does CSyncObject even represent?

Finally, note that CSyncObject will be destructed before CSingleLock which will attempt to unlock the destructed CSyncObject.

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke

Stuart Dootson31-Mar-09 12:22

31-Mar-09 12:22

Joe Woodbury wrote:
The "this" pointer should rarely be used in an initializer list.

It all depends whether he actually uses what the this pointer points at in the constructor or just stores it for later use. Storing for later use? Yeah, you'll be OK.

Joe Woodbury wrote:
...the virtual table hasn't been set up at this point.

The vtable will be consistent with the definition of the base class in the base class constructor (see this Scott Meyers article[^] for confirmation).

However, you do need to be very careful and aware of what's happening...which is why I probably shouldn't have said the OP would be OK with using this.

Joe Woodbury wrote:
I also think your class is a mistake and misunderstands CSyncObject() and CSingleLock(). The point is that there is one synchronization object with multiple threads locking that object. That locking is done by instantiated CSingleLock() at the start of a scope and upon exit of that scope, CSingleLock will be destructed regardless regardless of how the scope was exited.

Yeah, I wasn't even looking that far Blush | :O

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

ForNow31-Mar-09 15:32

31-Mar-09 15:32

As Far CsingLeObject Being Distructed I can always Create on the Heap as it will exist for the Life time of the app

Since threads are always Coming and going it may not be a bad idea to have to around

Cedric Moonen31-Mar-09 20:19

Cedric Moonen

31-Mar-09 20:19

I think you need to redesign a bit your architecture. You first have the problems explained by Joe but it also feels completely wrong: your class IS a CSingleLock object and IS a CSyncObject ? This is akward. I guess you are trying to make something without really understanding what you are doing.

Maybe if you explain what you are trying to do (conceptually I mean, not low level code like here), we could help you design a better solution...

Cédric Moonen
Software developer

Charting control [v1.5]
OpenGL game tutorial in C++

ForNow1-Apr-09 2:42

1-Apr-09 2:42

As far as what Joe Pointed the Csync Object getting destroyed before the Lock Object

the thread is in constant loop while(1) waitting to get signalled so it never ends

What I was trying to do since a CSingleLock needs a CsyncObject pointer make it all part of

one SuperClass

as said my code is a thread waitiing to get signaled when it does I single thread via the Lock

until the code finishes executing

thnakx

Stuart Dootson31-Mar-09 21:44

31-Mar-09 21:44

Following Cedric's response (which is quite correct) that your class shouldn't be both a lock and a sync object, here's a further suggestion that avoids both that confusion and the use of this in constructor calls.

Look at this page from Boost[^] describing the 'base-from-member' idiom.

Now, you could re-factor your code as:

struct mylock_pbase
{
   mylock_pbase() : syncObject(NULL) {}
   CSyncObject syncObject;
};

class mylock : private mylock_pbase, public CSingleLock
{
public:
   mylock(BOOL bInitialLock) : mylock_pbase(),
                               CSingleLock(&syncObject, bInitialLock)
   {
   }
   BOOL Unlock();
};

You could use the boost::base_from_member class, but it would only remove the need to declare mylock_pbase.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

ForNow1-Apr-09 16:05

Re: Multiple Inheritance question [modified]

1-Apr-09 16:05

I understand your just mylockphase create a CsyncObject named syncobject

IS there a need for the : syncobject(NULL) wont the CsyncObject get created without it

btw what does the "explicit" qualifer in Font of the CSyncObject signify

Stuart Dootson1-Apr-09 21:26

1-Apr-09 21:26

ForNow wrote:
syncobject(NULL)

I put that there because you had it in your original post Smile | :)

ForNow wrote:
btw what does the "explicit" qualifer in Font of the CSyncObject signify

That the constructor can't be used (by the compiler) to perform implicit type-casts. It only really matters for single parameter constructors and should probably be used for most single-parameter constructors just to make sure you don't create objects unless you really meant to. Look at the documentation for it[^].

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

modified on Thursday, April 2, 2009 3:33 AM

ForNow2-Apr-09 2:48

Vc++6.0. ADO. When I link in RELEASE mode I get Unresolved External error on ADO.

2-Apr-09 2:48

thankx

Antonio292931-Mar-09 5:32

Antonio2929

31-Mar-09 5:32

Hello. I have an application in VC++6.0 with MFC. I use ADO for Read/Write on file *.mdb.
When I link in DEBUG mode is OK.
When I link in RELEASE mode I get this error.
Which *.lib I must adding in link parametr? Or I must adding line code in my code source?

Thanks

error LNK2001: unresolved external symbol __imp__CoUninitialize@0
error LNK2001: unresolved external symbol __imp__CoInitialize@4
error LNK2001: unresolved external symbol "void __stdcall _com_issue_error(long)" (?_com_issue_error@@YGXJ@Z)

error LNK2001: unresolved external symbol "unsigned short * __stdcall _com_util::ConvertStringToBSTR(char const *)" (ConvertStringToBSTR@_com_util@@YGPAGPBD@Z)

error LNK2001: unresolved external symbol "char * __stdcall _com_util::ConvertBSTRToString(unsigned short *)" (?ConvertBSTRToString@_com_util@@YGPADPAG@Z)

error LNK2001: unresolved external symbol "void __stdcall _com_issue_errorex(long,struct IUnknown *,struct _GUID const &)" (?_com_issue_errorex@@YGXJPAUIUnknown@@ABU_GUID@@@Z)

error LNK2001: unresolved external symbol __imp__CLSIDFromProgID@8
error LNK2001: unresolved external symbol __imp__CLSIDFromString@8
error LNK2001: unresolved external symbol __imp__OleRun@4
error LNK2001: unresolved external symbol __imp__CoCreateInstance@20
fatal error LNK1120: 10 unresolved externals
Error executing link.exe.

Re: Vc++6.0. ADO. When I link in RELEASE mode I get Unresolved External error on ADO.

David Crow31-Mar-09 5:43

Re: Vc++6.0. ADO. When I link in RELEASE mode I get Unresolved External error on ADO.

31-Mar-09 5:43

Antonio2929 wrote:
When I link in DEBUG mode is OK.
When I link in RELEASE mode I get this error.

Check your linker settings to make sure Debug and Release match.

Antonio292931-Mar-09 6:12

Antonio2929

31-Mar-09 6:12

In DEBUG mode I use default libreries.
In RELEASE mode I must check "Ignore all default libreries" otherwise I get other error: type redefinition, ecc ecc..

Re: Vc++6.0. ADO. When I link in RELEASE mode I get Unresolved External error on ADO.

Stuart Dootson31-Mar-09 7:12

how to set breakpoint in this way?

31-Mar-09 7:12

Antonio2929 wrote:
In RELEASE mode I must check "Ignore all default libreries" otherwise I get other error: type redefinition, ecc ecc..

No - you must not check Ignore all default libreries - you must work out why those other errors are occurring and then fix them. I suspect a mixing of C runtime libraries.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

George_George31-Mar-09 5:27

George_George

31-Mar-09 5:27

Hello everyone,

I want to set a break point and wants it to be triggered when a piece memory (begin address and length are known) are changed. I am working on Windows Server 2003 x64 platform. Either solution in Windbg or solution in Visual Studio are fine. My purpose is to monitor when the memory content is changed.

thanks in advance,
George

Re: how to set breakpoint in this way?

David Crow31-Mar-09 5:28

Re: how to set breakpoint in this way?

31-Mar-09 5:28

George_George wrote:
...solution in Visual Studio are fine.

Which version?

Stuart Dootson31-Mar-09 7:17