Reference an external C dll

[newtoncw]

Hello,

I am trying to reference an external C dll in my project, but I get some errors:

undefined reference to '_imp__FT_Open@8'
undefined reference to '_imp__FT_GetDeviceInfo@24'
undefined reference to '_imp__FT_Close@4'

In my .pro file I put:

LIBS += -L"lib/"
qtAddLibrary(ftd2xx)

The .dll and .h files are available from FTDI, to communicate with USB chip.

My project is in the attachments.

Anyone can help me?

Thanks.

[schnitzel]

Please ignore this post (even though it does work) - see post from ChrisW67 for correct solution

================================================
I'm using the same device, the following works for me:

Inside the .pro file:

INCLUDEPATH += c:/ftdidrv
...
LIBS += c:/ftdidrv/i386/libftd2xx.a

INCLUDEPATH += c:/ftdidrv
...
LIBS += c:/ftdidrv/i386/libftd2xx.a

To copy to clipboard, switch view to plain text mode 

btw: I created libftd2xx.a (perhaps a bit of a misnomer) as follows:

reimp -d ftd2xx.lib
This will create a file called FTD2XX.DEF, which then needs the leading underscore removed from all function names. Next issue the following command:

dlltool --input-def FTD2XX.def --dllname ftd2xx.dll --output-lib libftd2xx.a -k

your app will still need the dll, and I redistribute the one click FTDI CDM installer with my app. I just realized this will only work for i386 -

If you find a better way, I'd be quite interested

ps: reimp is part of mingw-utils. Download version 0.3, not 0.4.1 (this one didn't work for me)

[mcosta]

Are you sure your lib is compiled with the same compiler you use?

In example Visual C++ and GCC?

[schnitzel]

Are you sure your lib is compiled with the same compiler you use?

In example Visual C++ and GCC?

that's exactly what reimp is for.

[newtoncw]

I already used the reimp, but the errors are same

I dont know what to do

[schnitzel]

I already used the reimp, but the errors are same

I dont know what to do

did you follow the steps in my earlier post exactly?
Did you download and run the CDM installer?

[newtoncw]

did you follow the steps in my earlier post exactly?
Did you download and run the CDM installer?

Yes, I follow your steps and I follow the FTDI's installation guide, but I still get the same errors

Can you send me your dlls with the .a files? Or your test project?
My e-mail is newtoncw@hotmail.com

Thanks for your help

[schnitzel]

if you get the exact same error then you did not follow this step:

This will create a file called FTD2XX.DEF, which then needs the leading underscore removed from all function names

can you attach your project again?

[ChrisW67]

Given that the interface is declared ' extern "C" ' and the functions are not __stdcall there should not be any name mangling issues and no need for the reimp/dlltool stuff.

I don't know what "qtAddLibrary()" is: cannot find it in my docs. Your PRO file should look like this:

LIBS += -L$$quote($$PWD/lib) -lftd2xx

LIBS += -L$$quote($$PWD/lib) -lftd2xx

To copy to clipboard, switch view to plain text mode 

and you do not need either the .def file or the resulting .a file. With just ftd2xx.dll and ftd2xx.lib in the lib directory this works just fine:

Y:\testeusb>dir /b lib
ftd2xx.dll
ftd2xx.lib
 
Y:\testeusb>qmake "CONFIG+=release"
 
Y:\testeusb>mingw32-make
mingw32-make -f Makefile.Release
mingw32-make[1]: Entering directory `Y:/testeusb'
g++ -c -O2 -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT
-DQT_DLL -DQT_NO_DEBUG -DQT_CORE_LIB -DQT_THREAD_SUPPORT -I"c:\Qt\2010.02.1\qt\i
nclude\QtCore" -I"c:\Qt\2010.02.1\qt\include" -I"c:\Qt\2010.02.1\qt\include\Acti
veQt" -I"release" -I"c:\Qt\2010.02.1\qt\mkspecs\win32-g++" -o release\main.o mai
n.cpp
g++ -enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-rel
oc -Wl,-s -Wl,-subsystem,console -mthreads -Wl -o release\testeusb.exe release/m
ain.o  -L"c:\Qt\2010.02.1\qt\lib" -LY:/testeusb/lib -lftd2xx -lQtCore4
mingw32-make[1]: Leaving directory `Y:/testeusb'
 
Y:\testeusb>dir /b release
main.o
testeusb.exe

Y:\testeusb>dir /b lib
ftd2xx.dll
ftd2xx.lib

Y:\testeusb>qmake "CONFIG+=release"

Y:\testeusb>mingw32-make
mingw32-make -f Makefile.Release
mingw32-make[1]: Entering directory `Y:/testeusb'
g++ -c -O2 -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT
-DQT_DLL -DQT_NO_DEBUG -DQT_CORE_LIB -DQT_THREAD_SUPPORT -I"c:\Qt\2010.02.1\qt\i
nclude\QtCore" -I"c:\Qt\2010.02.1\qt\include" -I"c:\Qt\2010.02.1\qt\include\Acti
veQt" -I"release" -I"c:\Qt\2010.02.1\qt\mkspecs\win32-g++" -o release\main.o mai
n.cpp
g++ -enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-rel
oc -Wl,-s -Wl,-subsystem,console -mthreads -Wl -o release\testeusb.exe release/m
ain.o  -L"c:\Qt\2010.02.1\qt\lib" -LY:/testeusb/lib -lftd2xx -lQtCore4
mingw32-make[1]: Leaving directory `Y:/testeusb'

Y:\testeusb>dir /b release
main.o
testeusb.exe

To copy to clipboard, switch view to plain text mode 

[schnitzel]

@ChrisW67 you're right - I just did a rebuild of my app. I'm not sure why I went down that road of using reimp - I guess I was trying to create a static lib and failed as it still required the dll. I then just left it at that.

[newtoncw]

Thanks @schnitzel, I really had forgotten that step

@ChrisW67, this works fine

Now its all ok

Thanks guys

[ikalogic]

I am sorry to revive this thread .. but the thing is that i have the same symptoms, but not the same solution...

I also get this error when compiling:

C:\...\testeusb\main.cpp:22: error: undefined reference to `_imp__FT_Open@8'

Even though i modified the .pro file with that line:

LIBS += -L$$quote($$PWD/lib) -lftd2xx

LIBS += -L$$quote($$PWD/lib) -lftd2xx

To copy to clipboard, switch view to plain text mode 

FYI, I downloaded the project file inlcuded in this thread, so i am assuming something is wrong with my compiler..? (since all user here seem to be able to compile it..)

I am using QT 4.8.1 with mingw.

Thank you very much.