free unmanaged resource from managed code

  • Thread starter Thread starter LeXave
  • Start date Start date
L

LeXave

Hi all

In C++/CLI, is there a way to free an array allocated from an
unmanaged dll ? In my managed code, I call a function from that dll
which returns me an array of bytes. But how can I free it ?

Thanks
 
In C++/CLI, is there a way to free an array allocated from an
unmanaged dll ?
Click to expand...

Only if you know (and have the exact same access to) the memory
manager that allocated it.
In my managed code, I call a function from that dll
which returns me an array of bytes. But how can I free it ?
Click to expand...

More details and a short example are probably needed before a
definitive answer can be given.

Dave
 
More details and a short example are probably needed before a
definitive answer can be given.
Click to expand...

in my unmnaged dll :

int *function()
{
int *a = new int[16];
// fill array, etc...
return a;
}

in my managed dll (C++/CLI):

tab = function();
// misc. operations with tab...
delete[] tab; // error

so, in my managed dll, once I finish to play with tab, I have to free
it, but my complier don't like my delete[]
 
LeXave said:
More details and a short example are probably needed before a
definitive answer can be given.
Click to expand...

in my unmnaged dll :

int *function()
{
int *a = new int[16];
// fill array, etc...
return a;
}

in my managed dll (C++/CLI):

tab = function();
// misc. operations with tab...
delete[] tab; // error

so, in my managed dll, once I finish to play with tab, I have to free
it, but my complier don't like my delete[]
Click to expand...

LeXave:

Are you sure that both DLL's are using the same version of the CRT?

But, personally, I do not like this mixed new/delete across DLL
boundaries. What happens if you export another function from your
unmanaged DLL:

void free_function(int* a)
{
delete [] a;
}

and call it from your managed DLL?
 
Dave,
What happens if you export another function from your
unmanaged DLL:
Click to expand...

It would certainly be the best solution, but the problem is that I
don't own the source of that dll, so I can't modify it :(

Both dll use the same version of the CRT (compiled both with VS 2005)
 
Both dll use the same version of the CRT (compiled both with VS 2005)

You can't mix debug & release components (they have different heaps),
and they both have to be built to use the DLL CRT option.

Dave
 
It would certainly be the best solution, but the problem is that I
don't own the source of that dll, so I can't modify it :(
Click to expand...

Then a better solution would be to create your own C++/CLI wrapper around the DLL to put a managed front face to it. For example,
you could copy the int[] array to a managed array, then delete[] the unmanaged array before returned the managed array.
 
Brian Muth said:
It would certainly be the best solution, but the problem is that I
don't own the source of that dll, so I can't modify it :(
Click to expand...

Then a better solution would be to create your own C++/CLI wrapper around
the DLL to put a managed front face to it. For example, you could copy the
int[] array to a managed array, then delete[] the unmanaged array before
returned the managed array.
Click to expand...

As I understand the original post, that's exactly what's not working.
Perhaps the original DLL has statically linked the CRT and returned pointers
allocated by that static CRT, in which case there is no way to safely free
the memory.
 
As I understand the original post, that's exactly what's not working.
Perhaps the original DLL has statically linked the CRT and returned pointers
allocated by that static CRT, in which case there is no way to safely free
the memory.
Click to expand...

Aaggh. That makes sense.
 
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