FFTW threads: ld: error: undefined symbol: fftwf_threads_set_callback

[fjrdev]

I want to use FFTW for an Android NDK project. Therefore I build with the following flags

./configure --host=aarch64-none-linux-android33 --enable-threads --enable-float sudo make sudo make install

After linking the library with: -L/path/to/fftwf/.libs/ -lfftw3f_threads -lfftw3f -lm, I get the following linking error when compiling: ld: error: undefined symbol: fftwf_threads_set_callback.

Is there anything else I have to consider when cross-compiling on MacOS for aarch64 android? I could not find anything in the documentation regarding this.

[stevengj]

If I recall correctly, the library isn't renamed to libfftw3f until it is installed?

Generally you should do a make install (set the --prefix to some local directory if you don't want to install systemwide) rather than trying to link into the .libs directory.

[fjrdev]

@stevengj Thanks for your help! I cross-compiled the library on a silicon mac for armv8a. So the library is already named libfftw3f.a when I push it onto the android device. I get the error when I link .lib inside the NDK application (in build.gradle).

The error occurs in tests/fftw-bench.c:

ld: error: undefined symbol: fftwf_threads_set_callback
>>> referenced by fftw-bench.c:101   (/path/to/fftwf_3.3.10/tests/fftw-bench.c:101)
>>>               fftwf_3.3.10/CMakeFiles/bench.dir/tests/fftw-bench.c.o:(useropt)

It seems like fftwf_threads_set_callback the first call to a thread-related function in fftw-bench.c, so I assumed it might be my build-process that resulted in this error.

[rdolbeau]

You may first want to check if the symbol is in the library or not (e.g. using 'nm'). If it isn't (or under the wrong prefix) it's a build problem. If it is, then it might just be a link command issue, and for static library sometimes changing the order help (i.e. put fftw3f before fftw3f_threads)