openACC pgc++ vs pgcc, error at linking

Question

I downloaded the example from https://www.olcf.ornl.gov/tutorials/mixing-openacc-with-gpu-libraries/ The codes are given in the above mwntioned links

1) using pgcc

pgc++ -c cuFFT.cu
pgcc -acc   -Mcudalib=cufft fft.c cufft.o
works perfectly fine

2) using pgc++

pgc++ -c cuFFT.cu
pgc++ -acc   -Mcudalib=cufft fft.cpp (or .c samefiles) cufft.o

I get the following error

    undefined reference to launchCUFFT(float*, int, void*)
     pgacclnk: child process exit status 1: /usr/bin/ld

Answer 1

You're running into a C/C++ linking mismatch.

To get this to work in PGI 17.9 tools I had to:

1. rename cuFFT.cu to cuFFT.cpp

2. edit the malloc line in fft.c from:

   float *data = malloc(2*n*sizeof(float));
   

   to:

   float *data = (float *)malloc(2*n*sizeof(float));
   

3. modify the declaration in fft.c from:

   extern void launchCUFFT(float *d_data, int n, void *stream);
   

   to:

   extern "C" void launchCUFFT(float *d_data, int n, void *stream);
   

4. Issue the following compile commands:

   $ pgc++ -c cuFFT.cpp
   $ pgc++ -acc   -Mcudalib=cufft fft.c cuFFT.o