Memory allocation

[Andy Baker]

I have recently written a .NET wrapper for a C++ DLL file and it seems to be
working well, but I do have some concerns about memory. From my limited C
programming experience (college 15+ years ago), I seem to remember that when
using structures etc in C, you had to allocate memory to them then
deallocate them when you had finished using them. My C# code creates a
variable of type structure, passes it to the C++ DLL and then returns
whatever data is necessary, without deallocating the structure reference. I
tried setting it to null, but the compiler wouldn't accept that as it said
it was a value type. Do I actually need to do anything or does the automatic
garbage collection take care of it for me? One thing I have to avoid is a
memory leak every time I make a call to the DLL. I am using VS 2005 and the
compact framework (2.0). Thanks in advance.

Andy Baker

[Pavel Minaev]

On Jul 21, 1:04*pm, "Andy Baker" <[e-mail]:

I have recently written a .NET wrapper for a C++ DLL file and it seems tobe
working well, but I do have some concerns about memory. From my limited C
programming experience (college 15+ years ago), I seem to remember that when
using structures etc in C, you had to allocate memory to them then
deallocate them when you had finished using them. My C# code creates a
variable of type structure, passes it to the C++ DLL and then returns
whatever data is necessary, without deallocating the structure reference.I
tried setting it to null, but the compiler wouldn't accept that as it said
it was a value type. Do I actually need to do anything or does the automatic
garbage collection take care of it for me? One thing I have to avoid is a
memory leak every time I make a call to the DLL. I am using VS 2005 and the
compact framework (2.0). Thanks in advance.

First of all, C# structs are not allocated on the heap (except when a
struct is a field of a class), but on the stack. You no more need to
free that than you need to free a local variable of struct type in C/C+
+. You may be confused by having to use the keyword "new" to
initialize the variable, but in C#, it does not perform heap
allocation when applied to value types - rather, it is equivalent to
creating a stack-allocated temporary in C++.

Anyway, if you pass a struct as an argument to an unmanaged function,
you should not need to do any memory management. The only case where
it may be necessary is when the unmanaged function allocates some
memory, and returns pointer to it, assuming the caller will deallocate
- then you'll need to handle this manually.

[Bob Powell [MVP]]

If you're concerned that memory leaks may be a problem. For example if you
see rising memory allocation in TaskManager while your program is running,
Microsof Research have a new tool LeakDiak that will assist in finding them.

I have recently used this to good effect.

Here's a good blog article.

http://mcfunley.com/cs/blogs/dan/arc...12/11/674.aspx

--
--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

Find great Windows Forms articles in Windows Forms Tips and Tricks
http://www.bobpowell.net/tipstricks.htm

Answer those GDI+ questions with the GDI+ FAQ
http://www.bobpowell.net/faqmain.htm

All new articles provide code in C# and VB.NET.
Subscribe to the RSS feeds provided and never miss a new article.
"Andy Baker" <ab****@NOSPAMvanputer.comwrote in message
news:m-idnY92PbRzzRnVnZ2dneKdnZydnZ2d@plusnet...

>I have recently written a .NET wrapper for a C++ DLL file and it seems to
be working well, but I do have some concerns about memory. From my limited
C programming experience (college 15+ years ago), I seem to remember that
when using structures etc in C, you had to allocate memory to them then
deallocate them when you had finished using them. My C# code creates a
variable of type structure, passes it to the C++ DLL and then returns
whatever data is necessary, without deallocating the structure reference. I
tried setting it to null, but the compiler wouldn't accept that as it said
it was a value type. Do I actually need to do anything or does the
automatic garbage collection take care of it for me? One thing I have to
avoid is a memory leak every time I make a call to the DLL. I am using VS
2005 and the compact framework (2.0). Thanks in advance.

Andy Baker