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thelonesquirrely wrote: then we were thinking if it was safe to create a lock like this:
...
Lock l (Mutex m);
...
correct me if I am wrong, but then m is scoped with l. This works if I only want m to exist for l.
No, that's incorrect. You're declaring a function, l, which takes a Mutex parameter called m and returning a lock. You cannot declare and define a variable in a function call. To demonstrate this, run this code:
#include <iostream>
class Mutex
{
public:
Mutex() { std::cout << "Mutex::Mutex\n"; }
~Mutex() { std::cout << "Mutex::~Mutex\n"; }
};
class Lock
{
public:
Lock(Mutex& m) : m_(m) { std::cout << "Lock::Lock\n"; }
~Lock() { std::cout << "Lock::~Lock\n"; }
private:
Mutex& m_;
};
int main()
{
Lock l(Mutex m);
}
You'll get no output, because no objects are being created or destroyed!
thelonesquirrely wrote: Is there any taboo no-nos to doing the prior method? Some pitfalls I am not seeing?
The main pitfall is that you never define a Lock variable, so you're not going to get any locking behaviour.
Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p
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How to join search two data tables in different database by ado?
Thanks! 
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By using database.owner.table notation.
"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
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First,thank you,my friend!
However,how many _connection objects and _recordset objects should I use?
With great pleasure if you can show me some simple C++ code!
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jiabin_007_love wrote: However,how many _connection objects and _recordset objects should I use?
One of each should suffice.
"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
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DavidCrow wrote: One of each should suffice.
However,a _recordset object can only correspond to one _connection object, and one _connection object can only link one database.
I need operate two data table in different database in one sql operator.
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I have a created a C# windows service (Serv.exe) which is responsible for performing various tasks at the request of a running application (A.exe), some of these can take long periods of time and I need a way to know the status of my requested operation (running on the service) from the calling application (A.exe).
Currently the way I have started to implement this is by using the ControlService(handle, command, status) to send a custom command to the Service to perform the task being requested, I am also using QueryServiceStatus(handle, status) to get the status of the service from the SCM - so the basic plumbing is there and working.
Now the problem I have is, after sending my ControlService Command (which works fine) the calling application (A.exe) keeps running and, at a certain point, it needs to know if the task it requested of the service is finished or not - therefore I am looking for a way to Query the Service to report a custom status, not the standard running, stopped, pending, paused state of the actual service but the status of the request I made using the ControlService() request.
Is this at all possible?
Any help or hints would be immensily appreciated.
Thanks,
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Is it possible to intercept the WinMM PlaySound function?
I seem to recall from ages past how to hook Windows API calls, but I'm not sure that I remember that correctly.
Marc
Will work for food.
Interacx
I'm not overthinking the problem, I just felt like I needed a small, unimportant, uninteresting rant! - Martin Hart Turner
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Hi Marc,
Absolutely. I believe the PlaySound Function[^] is exported from winmm.dll and is a wrapper for PlaySoundW so you could just hook PlaySoundW and get both. The Microsoft Detours[^] works very well although I believe it requires a licence for commercial use. There are also many free libraries (some here on codeproject) but your product support with free libraries may be limited or non-existent.
Best Wishes,
-David Delaune
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Greetings, I'm using MS SAPI for speech recognition in my project. I have the TTS and
the Standard Speech Recognition working perfectly, but I'm now trying to use the
dynamic Grammar interface or the "grammar builder".
The problem I think is with the ISpGrammarBuilder pointer that I am using in this code snipped:
CComPtr<ISpGrammarBuilder> cpGrammarBuilder;
SPSTATEHANDLE hStateTravel;
hr = cpGrammarBuilder->GetRule(L"Travel", 0, SPRAF_TopLevel | SPRAF_Active, TRUE, &hStateTravel);
I'm basing this code on this MS example code.
The code compiles correctly but I always get this Debug Assertion Failure on line 172 in atlcomcli.h or this function:
_NoAddRefReleaseOnCComPtr<T>* operator->() const throw()
{
ATLASSERT(p!=NULL);
return (_NoAddRefReleaseOnCComPtr<T>*)p;
}
Can anyone tell me what this function does? and if I'm using this ISpGrammarBuilder pointer correctly?
Any help is greatly appreciated
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You never assign the pointer a value - that's why you get the assertion failure. The Microsoft example omits that rather important step
Largo65 wrote:
_NoAddRefReleaseOnCComPtr<T>* operator->() const throw()
{
ATLASSERT(p!=NULL);
return (_NoAddRefReleaseOnCComPtr<T>*)p;
}
Can anyone tell me what this function does? and if I'm using this ISpGrammarBuilder pointer correctly?
This function implements CComPtr's operator->, allowing you to use the underlying interface pointer's methods through the managed pointer. All it needs to do is return something which also has an operator->, whether implicitly defined (i.e. a pointer) or explicitly defined (a struct/class).
Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p
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I was a little bit bored and tried this inline asm example:
Calling C Functions in Inline Assembly MSDN
But I get this error :
"Unhandled exception at ... Access violation writing location..."
at the instruction after the call instruction, even if I insert a NOP there.
Started with a vs2005 win32 console project and I copy pasted the code in "main" to my "_tmain" function
and declared the strings outside the main function
Another function that I created before did work (I think, didn't got any errors  ):
int increase (int a)
{
return ++a;
}
....
push 1
call increase
pop ebx
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This is happening because you are dynamically linking with the C runtime. Change the assembly code in the Microsoft example to:
call DWORD PTR printf
Another way to fix it is to change your C runtime linking to /MT or /MTd
Best Wishes,
-David Delaune
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thankyouverymuch , works now.
now I just have to figure out why it works
call printf
call DWORD PTR printf
So does this means that the first call instruction wants to use the "__imp__printf" directly
as an address where the printf function is?
And the second call instruction uses __imp__printf as a pointer to this addres?
I suppose it is like this because the address of the printf function is unkown before runtime
because the library is dynamically linked?
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Sounds like you pretty much understand why the Microsoft sample failed. Here is an old MSDN article with more info:
__declspec(dllimport) and __declspec(dllexport)[^]
invader82 wrote: now I just have to figure out why it works
Ahhh but isnt it great learning something new? Here are two more ways you could have fixed the Microsoft sample assembly code. I leave it as an excercise to the reader to figure out why it works.
[Method 1]
call dword ptr [esi+printf]
[Method 2]
mov esi,printf
call esi
Feeling like a programming dinosaur,
-David Delaune
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thx for the article very usefull 
Method 1 doesn't work and I don't see how it could work.
It uses the value of esi as a base address and adds the printf function address to it
I guess this would only work if esi == 0
method 2 is quite straight forward. it just puts the address of the function into esi
and performs an indirect call to that function using the addres in esi.
thanks anyway
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Gajendra Sharma wrote: Is it true also for Unix Sockets
It is.
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Gajendra Sharma wrote: Is it true also for Unix Sockets?
Sockets are not platform/OS dependent.
It is a crappy thing, but it's life -^ Carlo Pallini
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Gajendra Sharma wrote: Is it true also for Unix Sockets?
Yes.
The Microsoft implementation was originally designed/derived from Unix Berkeley sockets[^] and for the most part they are compatiable. There have been many Windows specific extensions in Microsoft Winsock2 but for standard TCP/IP and UDP they are nearly identical implementations.
Best Wishes,
-David Delaune
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Thanks all for the valuable replies.
Best Regards.
Gajendra Sharma
Gajendra
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I want to use an ocx in Vista session 0 using hidden window/dialog. This is giving me crash consistently. Has anyone tried this successfully?
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Hello,
i have the following problem that i want to describe with codesnippets:
i have the class CGCxPageElement. Its the Base class of CGCxPane:
class CGCxPageElement : public CGCxHtmlTemplate {
DECLARE_DYNCREATE(CGCxPageElement)
public:
CGCxPageElement();
CGCxPageElement(const CGCxPageElement &e) {
m_strTemplate = e.m_strTemplate;
m_strContent = e.m_strContent;
}
CGCxPageElement& operator=(const CGCxPageElement &e) {
m_strTemplate = e.m_strTemplate;
m_strContent = e.m_strContent;
return *this;
}
virtual ~CGCxPageElement();
protected:
CString m_strContent;
public:
virtual void SetContent(CString strContent);
virtual void SetContent(UINT nIDResource);
virtual CString MakeHtml();
};
class CGCxPane : public CGCxPageElement {
DECLARE_DYNCREATE(CGCxPane)
public:
CGCxPane();
CGCxPane(const CGCxPane &e) {
m_strTemplate = e.m_strTemplate;
m_strContent = e.m_strContent;
m_strTitle = e.m_strTitle;
}
CGCxPane& operator=(const CGCxPane &e) {
m_strTemplate = e.m_strTemplate;
m_strContent = e.m_strContent;
m_strTitle = e.m_strTitle;
return *this;
}
virtual ~CGCxPane();
protected:
CString m_strTitle;
public:
void SetTitle(CString strTitle);
virtual CString MakeHtml();
};
then i have an array of CGCxPageElement objects. i have to add GCxPane and other Object inherited from CGCxPageElement to it:
CArray<CGCxPageElement, CGCxPageElement&> m_Elements;
now here comes the problem: inside another class i want to go through the CGCxPageElement array and call the method MakeHtml, but not that one of the base class but of the child e.g. CGCxPane
for (int i = 0; i < m_Elements.GetCount(); i++) {
CGCxPageElement elem = m_Elements[i];
strContent.Append(elem.MakeHtml());
}
1. how can i find out what class is stored in m_Elements originally?
2. how can i call the MakeHtml() method of this class and not of the base class?
i am not a pro in inheritance...but for now i am stuck. any casting like
CGCxPane pane = (CGCxPane) m_Elements[i];
does not work and i don't want to hadrcode the CGCxPane inside because there will be some more CGCxPageElement object not only CGCxPane.
any help would be much appreciated!
regards,
rudi
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That's exactly the purpose of polymorphism. What you have to store in your array, is in fact pointers to the base class:
CArray<CGCxPageElement*> m_Elements;
Then if you have several different children of CGCxPageElement, you can simply create them and store them in the array (a pointer to a child class is also a pointer to the base class):
CGCxPageElement* pNewElement = new CGCxPane();
m_Elements.Add(pNewElement);
Then, if you make your MakeHtml function virtual, you can simply iterate over the array and call the function. It will automatically call the function from the correct type.
Don't forget to delete the elements from the array when you remove them.
I suggest you search a bit for polymorphism and C++ to have a better understanding of it.
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