I couldn't think a good title for this.Simple question
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Such is often used to define a build specific calling convention (Calling convention - Wikipedia[^]). In your case it seems to be defined in snap7.h[^]:
#ifdef OS_WINDOWS
define S7API __stdcall
#else
define S7API
#endif
I don't know how it got there. It is not Qt related and the QtCreator is probably ignoring it. It looks like you have copied the function definition from somewhere into your header file.
I added .h .c and .lib in my project so,so that it is defined in qt
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This is not a C language issue, it is something to do with Qt. S7API is a define variable that will be in one of the Qt header files, and perhaps also in the documentation.
This is in snap7 files
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I added .h .c and .lib in my project so,so that it is defined in qt
Then there is no need to re-define and re-implement the function when already located in a library or an additional source file which has been added to the project. However, I think pointing to calling conventions should have answered your question.
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Then there is no need to re-define and re-implement the function when already located in a library or an additional source file which has been added to the project. However, I think pointing to calling conventions should have answered your question.
The function that I indicate above is related the example that it is client .I did just copy past properly.I wrote about calling convention and it say me ,you have to use macro with in .h and .c (prototype and function).Now, Qt didnt add the macro with function .I suppose I have to add .Am I right
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The function that I indicate above is related the example that it is client .I did just copy past properly.I wrote about calling convention and it say me ,you have to use macro with in .h and .c (prototype and function).Now, Qt didnt add the macro with function .I suppose I have to add .Am I right
Don't add the macro to a Qt class function. You have two choices:
- Use the existing header and source files from the examples and add them to your project. Then call the function using the name and include the header file in the source files where you call it.
- Convert the examples by implementing all the code in Qt classes (source and header).
I would go for the first option. Than there is no need to implement a similar function as Qt class member. You might do so, but then the Qt function must not use the macro:
// MainWindow.h
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
// No calling convention here because this is a Qt based C++ class member
void CliCompletion(void *usrPtr, int opCode, int opResult);
// ...
};//MainWindow.cpp
#include "snap7.h"
#include "MainWindow.h"
// Other includesvoid MainWindow::CliCompletion(void *usrPtr, int opCode, int opResult)
{
// Call the global implementation from other source file or library
::CliCompletion(usrPtr, opCode, opResult);
} -
Don't add the macro to a Qt class function. You have two choices:
- Use the existing header and source files from the examples and add them to your project. Then call the function using the name and include the header file in the source files where you call it.
- Convert the examples by implementing all the code in Qt classes (source and header).
I would go for the first option. Than there is no need to implement a similar function as Qt class member. You might do so, but then the Qt function must not use the macro:
// MainWindow.h
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
// No calling convention here because this is a Qt based C++ class member
void CliCompletion(void *usrPtr, int opCode, int opResult);
// ...
};//MainWindow.cpp
#include "snap7.h"
#include "MainWindow.h"
// Other includesvoid MainWindow::CliCompletion(void *usrPtr, int opCode, int opResult)
{
// Call the global implementation from other source file or library
::CliCompletion(usrPtr, opCode, opResult);
}So,You mean ,I must not use the macro because of the reason that you say.I added in my project .lib,.h,.c and Qt is handling this instead of me.I understand like this,I am new communication engineer this is why I dont know perfect C++. By the way I create a new function Clicompletion is the function that I create,I will use it any where. Maybe I got it wrong you.
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Don't add the macro to a Qt class function. You have two choices:
- Use the existing header and source files from the examples and add them to your project. Then call the function using the name and include the header file in the source files where you call it.
- Convert the examples by implementing all the code in Qt classes (source and header).
I would go for the first option. Than there is no need to implement a similar function as Qt class member. You might do so, but then the Qt function must not use the macro:
// MainWindow.h
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
// No calling convention here because this is a Qt based C++ class member
void CliCompletion(void *usrPtr, int opCode, int opResult);
// ...
};//MainWindow.cpp
#include "snap7.h"
#include "MainWindow.h"
// Other includesvoid MainWindow::CliCompletion(void *usrPtr, int opCode, int opResult)
{
// Call the global implementation from other source file or library
::CliCompletion(usrPtr, opCode, opResult);
}#ifdef OS_WINDOWS # define S7API __stdcall #else # define S7API #endif Because of I use windows C++,I dont have to this with my functions,right?
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So,You mean ,I must not use the macro because of the reason that you say.I added in my project .lib,.h,.c and Qt is handling this instead of me.I understand like this,I am new communication engineer this is why I dont know perfect C++. By the way I create a new function Clicompletion is the function that I create,I will use it any where. Maybe I got it wrong you.
You must not use the macro with Qt classes (and should not use it with C++ classes). If you have another source file (or library) where the function is implemented, there is no need to implement it again as
MainWindowclass member. It is even not necessary to use the macro when the function is part of a C++ source file in your project. It is only necessary when using a C library. Then the header file tells the compiler that the function in the library uses that calling convention and that it must create corresponding code when creating the assembly code for the function call. C and C++ might use different calling conventions (depends also on the used compiler). Therefore, a compiler must know the calling convention when a C function is called from C++ code. -
#ifdef OS_WINDOWS # define S7API __stdcall #else # define S7API #endif Because of I use windows C++,I dont have to this with my functions,right?
It depends. See also my above post. Such constructs are not necessary for C++. But they are required when calling C functions from C++ code depending on how the C code has been build. If the C code is part of your project and you set the project options to compile C code as C++ (that is: use the C++ compiler also for C code), there is no need for the macro. But if the C code has been compiled as C for Windows, it must be used.
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It depends. See also my above post. Such constructs are not necessary for C++. But they are required when calling C functions from C++ code depending on how the C code has been build. If the C code is part of your project and you set the project options to compile C code as C++ (that is: use the C++ compiler also for C code), there is no need for the macro. But if the C code has been compiled as C for Windows, it must be used.
As a result of these informations, as far as I understand,I can call the functions just with name that intellisense show me functions,so that no problem with snap7 and I can create functions as I always do.This would be strange with macro.