C / C++ / MFC

19-Nov-07 18:47

Hello everyone,

I am using Visual Studio 2005 and I am wondering whether we could debug into the global delete operator?

I have tried to debug by setting a break point to delete statement, but I could only debug into destructor.

My understanding is, when we call delete, the internal operations are,

1. invoking destructor;
2. invoking global delete operator.

Is my understanding correct?

For example,

<br />
class Foo {<br />
<br />
int i;<br />
<br />
public:<br />
<br />
	Foo()<br />
	{<br />
		i = 100;<br />
	}<br />
<br />
	~Foo()<br />
	{<br />
		i = 0;<br />
	}<br />
};<br />
<br />
int main (int argc, char** argv)<br />
{<br />
	Foo* f = new Foo();<br />
<br />
	delete f;  // can not debug inside<br />
<br />
	return 0;<br />
}<br />

thanks in advance,
George

Haroon Sarwar19-Nov-07 22:56

Haroon Sarwar

19-Nov-07 22:56

why don't you just place a break point in the destructor of the object?

George_George19-Nov-07 23:51

19-Nov-07 23:51

Thanks Haroon,

I can debug into the destructor, but can not debug into global delete operator.

regards,
George

Haroon Sarwar19-Nov-07 23:57

Haroon Sarwar

19-Nov-07 23:57

hmmm...actually its debugging into it fine on my end (in VS2003)...

George_George20-Nov-07 0:10

20-Nov-07 0:10

Hi Haroon,

You mean you can debug into the global delete operator in Visual Studio 2003 from delete <pointer> statement? I am using Visual Studio 2005.

regards,
George

Matthew Faithfull19-Nov-07 23:15

Matthew Faithfull

19-Nov-07 23:15

It's a little more complex than that, at least in a Debug build which is where you'll most likely be debugging. In order to debug into delete properly you need to have installed the CRuntime Source files when you installed Visual Studio ( They can probably be added afterwards form the CD ) and then you need to include their folder in the source paths for your project so the debugger can find the source.
delete is potentially a long and complex process depending on what you're deleting and even with all the source not every stage will be visible. Remember the compiler generates destructors for classes where you don't write one and these will get called but throw you into the disassembler because there is no source just injected machine language. Don't let this put you off. Smile | :)

Nothing is exactly what it seems but everything with seems can be unpicked.

George_George20-Nov-07 0:07

can anyone help me in event macros in excel

20-Nov-07 0:07

Thanks Matthew,

Through my study, I find the global delete operator is defined in dbgdel.cpp, and I have the source codes. I have tried to add it to the source folders by Source Files --> Add --> Existing Item, but in this approach, it will bring me more and more dependencies' error (e.g. can not find .h or something) when I build all the files (including deldbg.cpp) in my project. So I think it may be not the correct way to add the source to my project. Could you help to indicate in my situation what is the most appropriate way to add the source to my project please?

regards,
George

yaminisridaran19-Nov-07 17:11

yaminisridaran

19-Nov-07 17:11

I am trying to write event macros for excel in vb editor but it works when the excel is open but when i close and reopen the excel it does not work. can any one let me know what wrong i am doing in excel

S.Yamini

Re: can anyone help me in event macros in excel

Peter Weyzen19-Nov-07 21:22

Peter Weyzen

19-Nov-07 21:22

Where's the C++ question?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
<A HREF="http://www.soonr.com">SoonR Inc -- PC Power delivered to your phone</A>

Which is more efficient in C

KellyR19-Nov-07 16:37

KellyR

19-Nov-07 16:37

Hi, I'm wondering which of these is more efficient in C code:

Let's say I have a function:

int check(int x)<br />
{<br />
  int var;<br />
<br />
  var = calc_var(x);<br />
  <br />
  return var;<br />
}

Is it more efficient to make that "int var;" into "static int var;" or is it better to keep it as non-static? This is a single-threaded program and the "calc_var" function always returns a value so changing var to static will have exactly the same programmatic behavior, I'm just wondering which is actually a more efficient way to do it, since this "check(int x)" function is called all over the place constantly, sometimes hundreds of times per second.

Thanks!

Roger Broomfield19-Nov-07 17:24

Roger Broomfield

19-Nov-07 17:24

In my humble opinion negligible change in efficiency. The way to get more efficient code in that case is to do this
__inline int check(int x) { return calc_var(x); }
provided the compiler complies with the __inline hint it will remove "sometimes hundreds of times per second" of constructing and releasing a stackframe around the unnecessary function call.

Or even, at the risk of incurring the wrath of some of the other members here
#define check(x) calc_var(x)
which will guarantee the unnecessary function call and stackframe are eliminated

User 58385219-Nov-07 17:32

User 583852

19-Nov-07 17:32

int check(int x)
{
return calc_var(x);
}

would be better as the int is only copied once. If you need the value of calc_var() for further processing in check() I'd avoid a static as you will probably end up confusing the optimiser and wind up with worse machine code. In my limited experiance spending time on questions like this is often a waste of time.

KellyR19-Nov-07 18:38

KellyR

19-Nov-07 18:38

Sorry, I was sort of unclear with my question; the check function I posted is a simplistic example, the real function is about 600 lines long and is a lot more complex than just returning another function, so it's not as easy as just eliminating a variable declaration.

followait19-Nov-07 18:08

followait

19-Nov-07 18:08

A local variable is likely in the cache, so it is more effiecint.
A static one may be far from the current instruction.

KellyR19-Nov-07 18:38

KellyR

19-Nov-07 18:38

Ok, thanks!