LNK2019: unresolved external symbol __imp_fftw_execute referenced in function "private: virtual void __cdecl QFFT::run(void)"

[vakh]

I'm using FFTW in my project. it works with MinGW perfectly but now I want to change my compiler to MSVC (2019). so first I make .lib files according to this. then I add

LIBS += -L "C:\fftw\fftw-3.3.5-dll64" -lfftw3-3
INCLUDEPATH += "C:\fftw\fftw-3.3.5-dll64"

to my .pro but after compilation this error occurred:

error: LNK2019: unresolved external symbol __imp_fftw_execute referenced in function "private: virtual void __cdecl QFFT::run(void)" (?run@QFFT@@EEAAXXZ)

QFFT is my internal class and FFTW functions called in run function.
I think it cannot find the library file. what is the problem? Also I use "Add Library" to import this lib to my project but the error doesn't changed:

win32:CONFIG(release, debug|release): LIBS += -L$$PWD/../../../../../../fftw/fftw-3.3.5-dll64/ -lfftw3-3
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/../../../../../../fftw/fftw-3.3.5-dll64/ -lfftw3-3d
else:unix: LIBS += -L$$PWD/../../../../../../fftw/fftw-3.3.5-dll64/ -lfftw3-3

INCLUDEPATH += $$PWD/../../../../../../fftw/fftw-3.3.5-dll64
DEPENDPATH += $$PWD/../../../../../../fftw/fftw-3.3.5-dll64

FFTW directory in my PC:

[JonB]

@vakh
I don't know exactly what your problem is, but I do not think it is that it cannot find a library, you should get a different message for that I think (try commenting out your LIBS += ... line and see what error you then get), rather there is an issue in how it was compiled/linked. Maybe go look at how QFFT::run() references fftw_execute() and how the latter is defined. I will say that the code looks like it is over a decade old and was last tested against VS 2010.

[ChrisW67]

@vakh said in LNK2019: unresolved external symbol __imp_fftw_execute referenced in function "private: virtual void __cdecl QFFT::run(void)":

I'm using FFTW in my project. it works with MinGW perfectly but now I want to change my compiler to MSVC (2019). so first I make .lib files according to this. then I add
LIBS += -L "C:\fftw\fftw-3.3.5-dll64" -lfftw3-3
INCLUDEPATH += "C:\fftw\fftw-3.3.5-dll64"

Try removing the space following -L

If that fails post the entire set of linker command leading up to this failure.

[vakh]

@JonB I commented INCLUDEPATH and LIBS and seen same error messages:

error: LNK2019: unresolved external symbol __imp_fftw_execute referenced in function "private: virtual void __cdecl QFFT::run(void)" (?run@QFFT@@EEAAXXZ)
error: LNK2019: unresolved external symbol __imp_fftw_plan_dft_1d referenced in function "private: virtual void __cdecl QFFT::run(void)" (?run@QFFT@@EEAAXXZ)
error: LNK2019: unresolved external symbol __imp_fftw_destroy_plan referenced in function "private: virtual void __cdecl QFFT::run(void)" (?run@QFFT@@EEAAXXZ)
error: LNK2019: unresolved external symbol __imp_fftw_alloc_complex referenced in function "private: virtual void __cdecl QFFT::run(void)" (?run@QFFT@@EEAAXXZ)
error: LNK2019: unresolved external symbol __imp_fftw_free referenced in function "private: virtual void __cdecl QFFT::run(void)" (?run@QFFT@@EEAAXXZ)

It works properly with MinGW and it must works with MSVC too. so I think QFFT::run(void) is OK.

[vakh]

@ChrisW67 removing and adding INCLUDEPATH and LIBS doesn't affect the errors.

[vakh]

the problem was wrong changing name. after using lib.exe to convert libfftw3f-3.dll to libfftw3f-3.lib. after this I changed the libfftw3f-3.lib to fftw3f-3.lib to detected by QT. but it's wrong. the name must not changed and I used this in my .pro file.

# MinGW
#INCLUDEPATH += "c:\fftw\fftw-3.3.5-dll64"
#LIBS += -L "C:\fftw\fftw-3.3.5-dll64" -lfftw3-3

# MSVC
INCLUDEPATH += "c:\fftw\fftw-3.3.5-dll64"
LIBS += -L"C:\fftw\fftw-3.3.5-dll64" -llibfftw3-3

and now my FFTW folder contains these files: