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A quick hint, never use local variables in a thread proc. Just keep using dwsub-> even if this sounds not optimized.
Windows shared objects such like DCs can be locked using the WIN32 API.
Code sections can be locked for one thread only by using CriticalSection, Semaphore or Mutex. See MSDN.
She's so dirty, she threw a boomerang and it wouldn't even come back.
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Thanks for the hint but it still dont works...the struct itself is some kind damaged because when I debug the application, in the thread proc, dwsub seems to be damaged ...
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a possible solution:
in your example, the DRAWERSUB structure is defined on the stack...
So when you call the AfxBeginThread, the struct is valid. but before the thread starts, the method which called AfxbeginThread might end, and release the stack memory of the DRAWERSUB...
solution: either allocate it on the HEAP (using HeapAlloc) or make it a member variable of CGraphicFunc (but then you can only create one copy of the thread).
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Hi world
I want to share a variable into a dll and all application using this dll handle the SAME variable (not a copy)..
How to do that?
Thanks in advance.
Hello World!!!
from Raphaël
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use global atoms. Link on MSDN[^].
Btw, as long as you don't cross process boundaries, all dlls share the same address space, thus every variable pointer is available from anywhere.
She's so dirty, she threw a boomerang and it wouldn't even come back.
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I'm getting back into programming after a long time off, and may post a few... silly questions. OK, here goes... I'm creating a network simulator, using (among other things), a number of derived classes that share a common base class. Most access to these classes is obtained through the use of a pointer to the base class, accessing the derived class functionality. All well and good. I'm having trouble, when I want to make a copy of one of the derived classes with a pointer to the base class. What I get is a copy of the base class only!
Should I be able to make a copy of a derived class if I'm using a pointer to it's base class? If so, do I need to set up either the base class or the derived class in such a way as to enable this copy function?
Thanks.
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Hmmm
I couldn't reproduce your problem (I am using VC++.NET)
class B
{
public:
B()
{
a=100;
}
int a;
};
class D : public B
{
public:
D()
{
b=200;
}
int b;
};
int _tmain(void)
{
B* b1 = new D();
B* b2 = b1;
D* d = static_cast<D*>(b2);
printf("%d",d->b);
delete b1;
return 0;
}
Regards,
Nish
Author of the romantic comedy
Summer Love and Some more Cricket [New Win]
Review by Shog9
Click here for review[NW]
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This is a very common situation when dealing with abstract classes. The usual solution is to define a virtual clone member function in the base class like this:
class Base{
public:
virtual Base * clone()const=0;
...
};
class Derived: public Base
{
public:
virtual Base * clone()const
{
return new Derived(*this);
}
};
Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo
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Hi, I'm having trouble inserting data into a MySQL table.
char myid[50]="testid";
char myip[50]="testip";
char myname[50]="testname";
char mymessage[50]="testmessage";
mysql_query(&mysql,"INSERT INTO mytable (id, ip, name, message) VALUES('myid','myip','myname','mymessage')")
This should insert the data which my vars contains, but instead it inserts myid myip myname and my mymessage into the table, not the data.
I think my syntax is wrong, since the mysql_query inserts 'myid' and no "testid" as it should..
I need help on this
Oh by the way, I'm not using the MySQL++ wrapper.
Thanks for any help
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Anonymous wrote:
mysql_query(&mysql,"INSERT INTO mytable (id, ip, name, message) VALUES('myid','myip','myname','mymessage')")
That line is all wrong friend.
Use something like this :-
char sqlstr[512];<br />
sprintf(sqlstr,"insert into tablename(id,ip) values ('%s','%s')",myid,myip);
Now do :-
mysql_query(&mysql,sqlstr);
Regards,
Nish
Author of the romantic comedy
Summer Love and Some more Cricket [New Win]
Review by Shog9
Click here for review[NW]
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Thanks for your help. I never thought of that
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I want to get the IP of the DNS server on a local computer.
is there a general way to do this that will work on all windows flavours?
At First it thought of IPHlpApi.lib, but Ip Helper Library is not supported in win95...
obviously it is possible, because WinIPCFG displays that information...
please help, thanks!
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I think the easiest way is to read it from the registry. But even then you have to read different places on different versions of windows.
- Anders
Money talks, but all mine ever says is "Goodbye!"
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any expert pls kindly help me,
i've created a new control "uiCtrlListCtrl" from the window control "CListCtrl". and i've defined some new message handlers.
such as:
void uiCtrlListCtrl::OnItemchanged(NMHDR* pNMHDR, LRESULT* pResult){
...
CWnd* pwndParent = GetParent();
pwndParent->SendMessage(UI_WM_ITEMCHANGING);
...
}
i have two such new list controls in a dialog(m_lsclList1 and m_lsclList2), how can i tell which control is it from when i received such an UI_WM_ITEMCHANGING message?
my message map is defined as below:
ON_MESSAGE( UI_WM_ITEMCHANGING, OnItemChanging)
the message handling function is defined as:
void uiDlgFrm::OnItemChanging(WPARAM wParam, LPARAM lParam){...}
afraid haven't expressed my problem clear enough: how can i pass something through the message's parameters to know it's from m_lsclList1 or m_lsclList2?
thx a lot!
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In c++,I define a class named Tdate,
I can define object using "Tdate td;","Tdate td1(1);","new Tdate;","new Tdate(1);",
And I know I can't do "Tdate td();" because it looks like function,
But Can I do "new Tdate();"?
And more,in visual basic(sorry I am just for contrast),
"Dim td as new Tdate()" is popularly used,and I did not see "dim td as new Tdate"?
I want to find the answer in some programming books,but they always did not illustrate clearly.
So I want others' help,or could you introduce me some articles or documents that elaborate on object define.
Thanks.
this is my signature for forums quoted from shog*9:
I can't help but feel, somewhere deep within that withered, bitter, scheming person, there is a small child, frightened, looking a way out.
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Tdate td;
and
Tdate td();
are equivilant.
new Tdate td();
and
new Tdate td();
are equivilant.
The compiler is able to recognize they are not function calls by the context they are used in.
In VB, DIM td as new Tdate() creates an (unsized) array of Tdate objects.
Shog9
------
And on the pedestal, these words appear:
"My name is Ozymandias, King of Kings,
Look on my Works, ye Mighty, and despair!"
Nothing beside remains.
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Thanks Shog.
In a book I have just read said "Tdate td()" is not allowed.
Is it right that "Tdate td()" equals "Tdate td",and "new Tdate" equals "new Tdate()"?
In VB,what is the difference of the following three:
Dim td as new Tdate();
Dim td as new Tdate;
Dim td as Tdate;
Thanks.
this is my signature for forums quoted from shog*9:
I can't help but feel, somewhere deep within that withered, bitter, scheming person, there is a small child, frightened, looking a way out.
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zhoujun wrote:
In a book I have just read said "Tdate td()" is not allowed.
As Joaquín also pointed out, that is correct; i was wrong. (i guess i should probably stick to sleeping at 2:00am...)
new Tdate;
is equivilant to
new Tdate();
however.
zhoujun wrote:
In VB,what is the difference of the following three:
Dim td as new Tdate();
Dim td as new Tdate;
Dim td as Tdate;
The first one declares an array, but gives it no initial size (parentheses are used for arrays as well as function calls in VB)
Actually, i'm not possitive that the first line will work; the syntax seems a bit odd, even for VB, as new is used to instantiate objects, but as the array is initially empty, there is nothing to instantiate.
The second one declares and instantiates a Tdate object.
The third one declares, but does not instantiate a Tdate object; it will need to later be instantiated using new or CreateObject() .
Generally in VB6 the use of new in a declaration line is discouraged, as though it's function is to instantiate an object, it does not actually do so until it is first used, at which point it is difficult to gracefully handle failures. In VB.NET, this has been corrected.
(The VB forum would probably be the place to get more confident answers to VB questions...)
Shog9
------
And on the pedestal, these words appear:
"My name is Ozymandias, King of Kings,
Look on my Works, ye Mighty, and despair!"
Nothing beside remains.
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Unfortunately, Tdate td; and Tdate td(); are not equivalent. The latter, as the original poster rightly pointed out, is interpreted by the compiler as the declaration of a function with no arguments returning a Tdate , regardless of the context. It is a quirk of the language we have to live with
Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo
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Ooops! Thanks Joaquín; not sure what i was thinking last night...
Shog9
------
And on the pedestal, these words appear:
"My name is Ozymandias, King of Kings,
Look on my Works, ye Mighty, and despair!"
Nothing beside remains.
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Hi,
with regard to UrlEscape function, why do I get "'UrlEscape' : undeclared identifier" when I compile?
I do have the required version of "Shlwapi.dll".
I am running on Win2000.
Kindly Help.
Thanks,
John.
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It's declared in shlwapi.h (5.0 and higher).
She's so dirty, she threw a boomerang and it wouldn't even come back.
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I am programming with MSVC++ 5.0 and 6.0. Interestingly the Shlwapi.dll offers the UrlEscape function, but is not declared in the file Shlwapi.h as posted by Stephane. Perhaps you need the latest SDK.
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