Successful passing of struct to foreign function
Successful passing of struct to foreign function

Based on GSL's definition of a complex as 
typedef struct
  {
    double dat[2];
  }
gsl_complex;
I have defined defcstruct to match, defined the interface to
gsl_complex_abs, and can successfully call compute the absolute value
(magnitude) of complex numbers:
FSBV> (test-call #C(1.0d0 2.0d0))
2.23606797749979
FSBV> (test-call #C(3.0d0 4.0d0))
5.0

stassats/cffi,mcna/cffi,cffi/cffi,dkochmanski/cffi,3b/cffi,cffi/cffi,3b/cffi,dkochmanski/cffi,3b/cffi,attila-lendvai/cffi,stassats/cffi,stassats/cffi,dkochmanski/cffi,cffi/cffi,mcna/cffi,attila-lendvai/cffi