octave-3.2.0 configure and fftw3

[Wolfgang Pichl]

Hi,
there seems to be a bug in the octave-3.2.0 configure script which 
inhibits using an installed fftw3 library. In config.log I find the 
following:

configure:10240: checking for fftw_plan_dft_1d in -lfftw3
configure:10275: gcc -o conftest -g -O2    conftest.c -lfftw3  -lhdf5 -lz 
-lm  >&5
configure:10281: $? = 0
configure:10299: result: yes
configure:10303: checking for fftwf_plan_dft_1d in -lfftw3f
configure:10338: gcc -o conftest -g -O2    conftest.c -lfftw3f  -lhdf5 -lz 
-lm
>&5
/usr/lib64/gcc/x86_64-slamd64-linux/4.2.4/../../../../x86_64-slamd64-linux/bin/ld: 
cannot find -lfftw3f
collect2: ld returned 1 exit status

and at the end:

configure:34554: WARNING: FFTW library not found.  Octave will use the 
(slower)
FFTPACK library instead.

As far as I understand, this means: configure first checks the standard 
libfftw3 (which is double precision). It is present and detected, but 
after that the single-precision version libfftw3f is also searched. Of 
course, it does not exist, the fftw3 package does not allow to build and 
install versions for different precisions at the same time (at least not 
without nasty tricks). So configure decides to disable support for the 
external fftw3. './configure --help' does not show any option to override 
this behaviour.

I have tested this on x86_64 Linux (Slamd64 distribution), with fftw3 
built from the source and installed in /usr/local. Anyway, the problem 
looks quite platform-independent. Octave-3.0.5 does not have 
this problem, the fftw3 library is detected out of the box.

best regards
Wolfgang Pichl