Generate a DLL with __stdcall calling convention

[ramanujam]

Hi,

I am generating a shared library(DLL) in Windows using QT Creator. I am facing a problem with this shared library (DLL).

I have to generate a Library with __stdcall calling convention. By default it is created with __cdecl calling convention.

I want to override this calling convention.

Could you please help me to achieve this.

Thanks & Regards,
Ramanujam

[dbzhang800]

Hi Ramanujam,

Qt does not do anything magic for this. If you want to export the funcation with __stdcall, you should add "__stdcall" to the function, which is exactly the same as you do when you using pure C/C++.

Regards,

Debao

[ramanujam]

Hi Debao,

Thanks for your answer. Actually I am aware of __stdcall.
I will explain you the problem what I am facing.

I am using third party library where all functions are in __stdcall calling convention. Third party library is a static library and it has a header file.

Static library has a function
void __stdcall SomeFunction()
{
}

but in header file its prototype is
void SomeFunction();

What is happening is when I include header file in my Shared library(DLL) is
SomeFunction() is considered as __cdecl because __stdcall is missing from prototype declaration in header file and Shared library by default was compiled in __stdcall calling convention.

When I call SomeFunction() from my DLL it is giving a linker error because calling convention is mismatching with the function definition.

I contacted the third party vendor and they said I have to change the project settings to __stdcall (/Gz) compiler option. It will solve the problem. For testing purpose I changed the prototype declaration to
void __stdcall SomeFunction(); then Shared library is linking fine. But this is not the correct solution because third party library is licensed and I can't change the header file of a third party library.

I hope you understood the problem. What I want is how can I change the QT project settings to include __stdcall convention similar to Visual studio where you change the calling convention from Project-->Properties-->C/C++-->Advanced-->Calling Convention.

Basically what I need is How to include the library which uses __stdcall convention for all the functions with the DLL which uses __cdecl convention...............

Please help me.....

Thanks & Regards,
Ramanujam

[dbzhang800]

You can add following line to your .pro file.
@
QMAKE_CFLAGS += /Gz
QMAKE_CXXFLAGS += /Gz
@

Regards,

Debao

[ramanujam]

Thanks a lot....

Linking with third party library is fine now. But due this compiler option there is one more linker error in QString.

I have done one sample and below are the steps

1. Created a shared library to include QtCore modules
2. included QtCore in my cpp file and added
   QString test = QString::number(5000); to convert number into a QString.
3. Then added the
   QMAKE_CFLAGS += /Gz
   QMAKE_CXXFLAGS += /Gz
   int the .pro file
4. Rebuild entire project

There are linker errors for these QString. If I remove above options from a .pro file it links successfully.
My observation is accessing all static member functions of a class are giving linker error with this compiler option.
For Example:
quint64 g_ulCurrentPID = QCoreApplication::applicationPid();
Also my project settings include "UNICODE" and "No (/Zc:wchar_t-)". I tried with "treat _wchar_t as default Built-in Type" as Yes. Still I am facing the same problem.

Could you please help to solve this linker error

Thanks & Regards,
Ramanujam

[vsbrar]

I'm facing a similar problem changing calling convention to cdecl gives "Interlocked" errors in files qatomic_windows.h and intrin.h. I'm tried on Visual Studio using QT VS Plugin and QT Creator.

Steps to recreate:
Visual Studio

Create a QT console application.

VS properties -> Configuration Properties -> C/C++ -> Advanced -> Calling Convention.

Change to __stdcall (/Gz)

Qt Creator

Create a console or any other application

In the .pro file add the following lines

QMAKE_CFLAGS += /Gz
QMAKE_CXXFLAGS += /Gz

Build the project

Platform Details:
Windows 7 64 bit
Visual Studio 2010
QT Version 4.8.2