C / C++ / MFC

5-Nov-14 4:34

I would assume Qt has methods for all of this... have you checked out their documentation? Although from my own personal experience... I know their documentation isn't very good.

Static linking

Member 112017882-Nov-14 22:27

Member 11201788

2-Nov-14 22:27

Our application develped in C# uses a dll and static library(lib).
The dll is intermediate project for static libraty and C# application.

Client has provided files(library file and a dll) which is required for interacting with their application.
1. In our C++ static library we are using only the library file provided by client by statically linking it.
2. Our C++ wrapper dll references this C++ static library created in step 1.
3. C# application references the wrapper dll created in step 2.

Since the library file is statically linked in our C++ static library, does the dll also need to be linked/referred in our application.

Garth J Lancaster2-Nov-14 22:37

Garth J Lancaster

2-Nov-14 22:37

its not clear how the c# application (3) is using the c++ wrapper (2)

if you're using p/invoke, then the 'reference/link' is in the p/invoke statements themselves, ie, the DllImport clause

Richard MacCutchan2-Nov-14 23:09

2-Nov-14 23:09

If the C++ dll has been linked to the static library, then you only need access to that dll in your C# code (assuming I have understood the question correctly).

Albert Holguin3-Nov-14 11:31

3-Nov-14 11:31

Member 11201788 wrote:
Since the library file is statically linked in our C++ static library, does the dll also need to be linked/referred in our application.

Do you mean dll or lib at this point?
If you mean lib, then it should be a no, you don't need a reference to it while building your C# application. If you mean dll, then yes, your C# application does need a reference to your dll.

Member 112017883-Nov-14 23:31

Member 11201788

3-Nov-14 23:31

Since the library file(lib provided by client) is statically linked in our C++ static library, does the dll(lib provided by client) also need to be linked/referred in our application.

They(client) have provided their .lib and .dll. Can we use only .lib in our C++ static library.

Albert Holguin4-Nov-14 4:24

Template Class Pointer - Would like explanation for unexpected behavior

4-Nov-14 4:24

Member 11201788 wrote:
Since the library file(lib provided by client) is statically linked in our C++ static library, does the dll(lib provided by client) also need to be linked/referred in our application.

Shouldn't have to... if you load the lib into your dll properly.

Member 11201788 wrote:
They(client) have provided their .lib and .dll. Can we use only .lib in our C++ static library.

Again, should be able to just use the lib, since it's a collection of objects. Only thing that may be a limiter is that you have to use a lib that was compiled with the same compilation settings as your project, since the name mangling of C++ can affect you being able to find your methods. A lot of people tend to do their exports/imports in a C-style format even within C++ in order to avoid C++ name mangling issues.

Foothill2-Nov-14 8:01

Foothill

2-Nov-14 8:01

I am expanding my knowledge of class templates so I am building a very basic template of type Array<T>.
I'll include only the code that pertains to the behavior that is confusing me.

Template Header

C++

// MyArray.h

#include <stdexcept>

#define CORE_ARRAY_DEFAULT_LENGTH 20

template <class T>
class Array
{
private:
T** _array;
int _size;
int _length;

public:
Array(void)
{
_array = new T*[CORE_ARRAY_DEFAULT_LENGTH]();
_size = CORE_ARRAY_DEFAULT_LENGTH;
_length = 0;
}
~Array(void) { Clear(); }

int Size(void) const { return _size; }
int Length(void) const { return _length; }

T operator [] (int index) const
{
if ((index < 0) || (index >= _length))
   throw std::out_of_range("index");
else
   return * _array[index];
}

void Add(T value)
{
if (_length == _size)
   Resize();

_array[_length] = new T(value);
++_length;
}

/* Other functions follow CopyArray(), CloneArray(), Resize(), Clear(), InsertAt(), etc... */
}

And the source

C++

#include "MyArray.h"
#include <cstdlib>
#include <cstdio>

void main(void)
{
// This behaves as expected
Array<int> iArrayA;

for (int i = 0; i < 10; ++i)
   iArrayA.Add(i);
for (int i = 0; i < 10; ++i)
   printf("%d\n", iArrayA[i]);

// But this was returning odd results
Array<int> * iArrayB = new Array<int>();

for (int i = 0; i < 10; ++i)
   iArrayB->Add(i);  // confirmed that the values were stored correctly
for (int i = 0; i < 10; ++i)
   printf("%d\n", iArrayB[i];  // outputs were not what I expected

delete iArrayB;

system("pause");
}

Here is what I had to change it to to get the desired results:

C++

printf("%d\n", iArrayB[0][i]);

What I don't get here is why when the array was declared as a local (Array<int> iArrayA;) did the accessor [] pull the stored int at the correct element but when I had the array declared as a pointer on the heap (Array<int> * iArrayB = new iArray<int>();) the accessor [] was seemingly pulling random data until I added the [0] before the [i]?

I am wondering if this has something to do with overloading the array subscript operator. Which is what has jumped out at me while I am writing this.

Also, is there a way I can code the accessor to work for both locals and heap pointers? Is there any way around this?

Re: Template Class Pointer - Would like explanation for unexpected behavior

Richard MacCutchan2-Nov-14 8:13

Re: Template Class Pointer - Would like explanation for unexpected behavior

2-Nov-14 8:13

C++

private:
T** _array;

Why is this an array of pointers to T types, rather than just an array of T types? Woudl it not be better to have something like:

C++

T* _array;

// ...

_array = new T[CORE_ARRAY_DEFAULT_LENGTH];

// ...

T operator [] (int index) const
{
if ((index < 0) || (index >= _length))
   throw std::out_of_range("index");
else
   return _array[index];
}
// etc

Foothill2-Nov-14 8:44

Foothill

2-Nov-14 8:44

For one, I've designed it to create heap copies of everything that gets added. This way it can handle both primitive data types and objects and be able to delete them. My first attempt at this used this approach but I ran into problems when trying to handle objects created on the heap. You can't delete primitives and if you don't delete heap objects, it leaks memory. By making it create all of its data on the heap no matter what get's passed in, I can avoid this problem.

Edit: I got the T** _array; idea from my practice attempts with the DirectX SDK. I saw it use this approach all over the place.

Re: Template Class Pointer - Would like explanation for unexpected behavior

Freak303-Nov-14 2:50

Freak30

3-Nov-14 2:50

The reason for the different behvior is that you can only override the accessor [] for an instance or reference but not for a pointer. Using [] on a pointer is always interpreted as pointer + index by the compiler. So the compiler thinks you have an array of Array.

The usual syntax around this is

C++

printf("%d\n", (*iArrayB)[i]);

This makes clear that iArrayB isn't an array but a pointer to a single object, and that you want to call the operator for the object it points to.

The good thing about pessimism is, that you are always either right or pleasently surprised.

Re: Template Class Pointer - Would like explanation for unexpected behavior

Foothill3-Nov-14 5:59

Foothill

3-Nov-14 5:59

Ah, I was thinking that it was something along those lines. I can see now that overloading the subscript operator is only good in certain situations. This doesn't sound like a good approach since it would require different code to access the data behind an object pointer then behind a local variable. I'll just change the accessor to a function.

C++

T GetValueAt(int index)
{
if (index < 0 || index >= _length) 
   throw std::out_of_range("index"); 
return *_array[index];
}

This should work just fine for what I am trying to do.

This was informative, thank you.

Re: Template Class Pointer - Would like explanation for unexpected behavior

the_foobar3-Dec-14 20:26

the_foobar

3-Dec-14 20:26

Be careful, you are heavingly doing copy of your objects.
You should pass T& when you add the object and return T& when you retrieve them.
I would also suggest to have a const version of your accessor, returning 'const T&'.

Re: Template Class Pointer - Would like explanation for unexpected behavior

Volynsky Alex4-Nov-14 23:12

Volynsky Alex

4-Nov-14 23:12

Nice!

ERROR No Target Architecture

ForNow1-Nov-14 17:05

ForNow

1-Nov-14 17:05

Hi,

I VS 2012 as a makefile project in the nmake properties IntelliSense Preprocessor definitions I specify _AMD64_

Yet I get the following compile error
:\Program Files\Microsoft SDKs\Windows\v7.1\Include\winnt.h(135): fatal error C1189: #error : "No Target Architecture"

Re: ERROR No Target Architecture

Richard MacCutchan1-Nov-14 22:03

Re: ERROR No Target Architecture

1-Nov-14 22:03

It sounds as though your definitions are not being exported correctly, check the make file to see what it is setting.

ForNow2-Nov-14 4:04

ForNow

2-Nov-14 4:04

Thanks

I am wondering a on makefile visual studio build where a line command is used
what role do the preprocessor flags play in the build

thanjks

Re: ERROR No Target Architecture

Richard MacCutchan2-Nov-14 5:49

How to protect a member function

2-Nov-14 5:49

ForNow wrote:
what role do the preprocessor flags play in the build

No idea, but as I said earlier, you should look at the makefile to see whether this value has been propagated correctly.

Drugodrf31-Oct-14 4:35

Drugodrf

31-Oct-14 4:35

Hi to all,
i write a class (A) that works with an object from another class (B); class B needs to call a method from class A, but i would like this function from class A it's not visible when i use class A for my projects.
Example: i write a numeric edit that use spin button; i write a spin button class derived from CSpinButtonCtrl and an edit class derived from a CEdit; edit have a function MyFunction() called from spin button class.
So, when i use numeric edit in my projects, i would like MyFunction() (and also all class spin button) is not visible (protected).
What is the correct way to do that, if it's possible ?

Thanks

Jochen Arndt31-Oct-14 5:18

Jochen Arndt

31-Oct-14 5:18

It seems that you are looking for friend[^].

For your example you can make your CEdit derived class a friend class of the spin control class:

C++

class CMyEdit : CEdit {
 friend class CMySpinControl;
protected:
 // This can be called from CMySpinControl.
 void MyFunction();
};

image processing toolkits | batch image processing

C^hris L^osinger31-Oct-14 5:18

C^hris L^osinger

31-Oct-14 5:18

make MyFunction private, and make A a friend of B.

friend classes
[^]

Drugodrf3-Nov-14 2:31

Drugodrf

3-Nov-14 2:31

As i can, i try.

Thanks to all

Albert Holguin3-Nov-14 11:39