Re: Trouble with heap after call of DLL method

From:
"mlimber" <mlimber@gmail.com>
Newsgroups:
comp.lang.c++
Date:
11 May 2006 09:05:01 -0700
Message-ID:
<1147363501.888587.116600@u72g2000cwu.googlegroups.com>
bellerophon wrote:

I am having a serious trouble with my pointers in a programm that uses
dll and was hoping that somebody in this group could help me:

I export my DLL classes with declspec(dllexport) and link against them
using the lib-file. I do not use anything but stuff included in the C++
standard libraries (like iostream) so far.

In my calling application I first do

class __declspec(dllimport) Image {
 public:
 Image();
...

};

and afterwards I do

double * values = new double[9];
double values[0] = 0.0;
...
double values[8] = 0.0;

cout << "DEBUG: values is at address " << values << endl;
        Image im();

This does not invoke the constructor; it declares a function named "im"
returning an Image and taking no parameters. Thus, it should not invoke
your DLL at all.

cout << "DEBUG: deleting at memory address " << values << endl;
delete [] values;

The empty image constructor does nothing, not even initializing the
member variables with standard values. I tried to resimulate the
ever-reoccuring problem under a minimal environment and an in my
opinion an empty member constructor is such.

Now I fail to delete values. The output of the program is:

DEBUG: values is at address 003814C0
DEBUG: deleting at memory address 00381400

Obviously I am either overwriting the pointer to the array or I having
some other heap problem - which is really driving me crazy, since I
can't find the reason for it.
When I am calling a static (exported) function such as
Image::printHelloWorld(); the problem doesn't occur.

If I am initializing values from stack (double values[9]); values[0] is
overwritten after the DLL method call...

Can anybody tell me, what I seem to be missing here?

Thanks in advance


Show us a minimal but *complete* sample that demonstrates your problem.
If it is a C++ *language* issue, we'll try to help you. If it is a DLL
issue, you'll have to ask the Microsoft folks, as DLLs are off-topic in
this group. For what is on-topic and for some potential groups you
could pursue this in if it's not a language issue, see this FAQ:

http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.9

Cheers! --M

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