Managed C++/CLI

Garbage collection -- what's the trick?

24-Jul-03 1:43

How about this:

namespace oldCpp
{
 enum { myfirst = 0, mysecond };
}

public __value enum newMCpp { myfirst = oldCpp::myfirst, mysecond = oldCpp::mysecond };

Then you could do something like:

int oc = (int)newMCpp::myfirst;

Untested, but should hopefully get you started.

[edit] wrapped first enum in namespace. Learned this in another post in the VC forum. [/edit]

Hope this helps,
Nathan

---------------------------
Hmmm... what's a signature?

Jeremy Osner22-Jul-03 9:04

22-Jul-03 9:04

I noticed my program was leaking memory at a huge rate -- went in and did some debugging and it seemed pretty clear that managed memory was never being deallocated. After fretting for a while over why this should be so, I added a call System::GC::Collect() under certain circumstances. With this call in, there is no leak. Why shouldn't the gc have been collecting on its own -- isn't this the whole point of garbage collection?

READIN writin rhythmetic

Nathan Blomquist23-Jul-03 5:15

23-Jul-03 5:15

The garbage collector in .NET is a lazy collector. What this means is that it will not collect until it needs to. Only when memory is getting low, will it collect.

Check the MSDN for more info.

-Nathan

---------------------------
Hmmm... what's a signature?

Jeremy Osner23-Jul-03 5:28

23-Jul-03 5:28

Thanks, I guess I just wanted it do happen a bit before it would by default -- are there any caveats I should be aware of afa using GC::Collect()?

READIN writin rhythmetic

Nathan Blomquist23-Jul-03 6:21

23-Jul-03 6:21

Only a possible performance hit. How often are you calling a collect? A collection is very intensive operation since it has to go through all the objects in your process and see if they are to be collected.

-Nathan

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Hmmm... what's a signature?

Jeremy Osner23-Jul-03 6:58

23-Jul-03 6:58

Yeah, I figured it was an expensive call -- I am doing it quite infrequently, immediately after a call which I know results in a whole lot of objects being eligible for reclamation -- is that the correct terminology? I want to just say "I deleted a lot of stuff" but obviously I did not delete it, I just removed references.

READIN writin rhythmetic

Nathan Blomquist23-Jul-03 8:30

23-Jul-03 8:30

Jeremy Osner wrote:
eligible for reclamation

I think the phrase would be "eligible for collection", because "reclamation" to me sounds like you are recycling the objects themselves instead of just the memory. But I am sure that anyone you typed with or spoke to would readily understand Smile | :)

.

-Nathan

---------------------------
Hmmm... what's a signature?

Jeremy Osner23-Jul-03 8:41

23-Jul-03 8:41

Thanks for the help, Nathan!

READIN writin rhythmetic

Linker errors

Slaru21-Jul-03 17:20

21-Jul-03 17:20

Hey,
First of all, I would like to say with only being a member of this site for a little while, I have found it very useful. I am pretty much a newbie in programming and don't know much about compiler and linker errors. I get this error when trying to compile.

playSound.obj : error LNK2022: metadata operation failed (8013118D) : Inconsistent layout information in duplicated types (playSound): (0x02000005).

LINK : fatal error LNK1255: link failed because of metadata errors

Anybody know what this is? If you need source code I can give it. I am sure I included all the includes and libraries. Thanks.

Also does anybody know how to convert a String to a LPCWSTR? I hadn't heard of LPCWSTR before but appears to be some other kind of string.
example:

String * str = S"Hello";<br />
// Convert str to a LPCWSTR so I can pass it into a function<br />
<br />
somefunction(MyConvertedString)

Double thanks.

Jeremy Osner22-Jul-03 7:24

22-Jul-03 7:24

I can't answer your linker question but an LPCWSTR is a char pointer -- see the thread lower on this page regarding PtrToStringChars().

READIN writin rhythmetic

Slaru22-Jul-03 7:49

22-Jul-03 7:49

Thanks for answering my second question. Is there anyone who knows what my linker problem is or who can give tips to fix it?

jspano22-Jul-03 15:14

jspano

22-Jul-03 15:14

I believe that your first error is from a type that is defined 2x and differently each time. Check that in your playsound files.

Slaru22-Jul-03 17:10

Serial COM port in Managed C++

22-Jul-03 17:10

I have fixed both problems. Thanks. I made my class all inline and that fixed my linker errors whatever they were. Case closed.

icdma21-Jul-03 6:37

icdma

21-Jul-03 6:37

Has anyone implemented Albert's article, "How to open a serial COM port in Managed C++, By Albert Pascual"

After I boot up my WinXP Pro system, Albert's implementation only works after I start up HyperTerminal. After that, it works fine from then on... Any clues? Has anyone else run into this on XP.

Thanks in Advance!

Re: Serial COM port in Managed C++

icdma26-Jul-03 7:43

icdma

26-Jul-03 7:43

I worked through this. The code provided in the article is not sufficient to make the serial port work properly.

icdma

strange compiler error

Slaru20-Jul-03 13:06

Re: strange compiler error

20-Jul-03 13:06

Hi,
I am learning C++ and Windows Forms and get a strange compiler error. I am using the directX header dshow.h for my project and when I do I get this error:

error C2039: 'GetObjectA' : is not a member of 'System::Resources::ResourceManager'
stdafx.cpp(0) : see declaration of 'System::Resources::ResourceManager'

and it points to this code:

this->ButtonImages->ImageStream = (__try_cast<System::Windows::Forms::ImageListStreamer *  >(resources->GetObject(S"ButtonImages.ImageStream")));

and this was all generated by the designer.

I also get something similar when I try to use the MessageBox class. If I don't imclude dshow.h than these errors go away.

Any reasons and fixes are appreciated. Thanks.

Nemanja Trifunovic20-Jul-03 15:10

Nemanja Trifunovic

20-Jul-03 15:10

That's because preprocessors are stupid. When a preprocessor finds GetObject, it replaces it with GetObjectA or GetObjectW, depending whether you compile a Unicode version or not.

Just put something like

#undef GetObject

after #include <windows.h>
and everything should work fine.

static __gc[] @#$@

leppie19-Jul-03 22:04

19-Jul-03 22:04

Hi all

HTF do you declare it? Now I know why it is called C++, like C, but you are require to do 2 things extra for every bloody thing@!!!

OK so I had this in C:
static Int32 rNums[512] = { 123,1231,....,2131};
In MC++ I try:
static Int32 rNums __gc[] = {123,1231,....,2131};

No luck, Int32 is defined. The error messages are useless as usual! Compiling as C++ with /clr.

at the declaration:
randtable.c(71) : error C2146: syntax error : missing ';' before identifier 'rNums'
randtable.c(71) : error C3150: '[' : '__gc' can only be applied to a class, struct, interface, array or pointer

at the end of the array:
randtable.c(123) : error C2501: 'leppie::RandomNumbers::rNums' : missing storage-class or type specifiers
randtable.c(123) : error C3845: 'leppie::RandomNumbers::rNums' : only static data members can be initialized inside a __gc class or value type

ANy one?

leppie ::AllocCPArticle(Generic DFA State Machine for .NET);

leppie19-Jul-03 22:31

19-Jul-03 22:31

OK I dont get this...

AT stattement level I can do this:

Int32 rNums __gc[] = {11,112,334,...,6667,8567};
But NOT at class level for a static instance. Nor can I do assignment at statement level, ie:

Int32 rNums __gc[];<br />
<br />
rNums = {11,112,334,...,6667,8567};

According to the docs the behaviour is the same as C++...

leppie ::AllocCPArticle(Generic DFA State Machine for .NET);

Solved :)

leppie19-Jul-03 23:14

19-Jul-03 23:14

Had to add a const and it worked fine Smile | :)

I should have expected something like that!!! Mad | :mad:

leppie ::AllocCPArticle(Generic DFA State Machine for .NET);

Tom Archer20-Jul-03 3:32

Tom Archer

20-Jul-03 3:32

__value struct V
{
  static Int32 rNums[] = { 123, 345 };
  static String* names[] = { S"ABC", S"DEF" };
};

Cheers,
Tom Archer
Inside C#,
Extending MFC Applications with the .NET Framework
It's better to listen to others than to speak, because I already know what I'm going to say anyway. - friend of Jörgen Sigvardsson

leppie20-Jul-03 5:01

20-Jul-03 5:01

It doesnt appear to work so for a __gc class though, and what is the difference between:

__value struct<br />
__value class<br />
__gc class<br />
__gc struct

?

leppie ::AllocCPArticle(Generic DFA State Machine for .NET);