Scalar passing with call_external

All,

I am having a heck of a time with something here.  I am trying to
understand the behavior of a C routine that I am trying to call from
IDL.

Given this C code: (ctest.c)
void ctest ( float a, float b, float *c, float v[3] )
{
   float tmp;
   tmp = a*b;
   v[0] = tmp;
   v[1] = a-b;
   v[2] = a+b;
   *c = 66;
}

And this IDL code: (ctest.pro)
make_dll, 'ctest', 'ctest', 'ctest', compile_directory = '.'
a = 5.
b = 3.
c = [7.]
v = fltarr(3)
ans = call_external('ctest.so', 'ctest', a, b, c, v, /auto_glue, value
= [1, 1, 0, 0])
print, ans, a, b, c, v
end

I expect the output to be:
<undetermined>     5.0     3.0     66.0
     15.0       2.0    8.0

But instead I get:
IDL>  .run ctest
 -1073774376      5.00000      3.00000      7.00000
      15.0000      2.00000      8.00000

So the root of the question is how do I pass scalar information back
out of the C routine to the IDL?  As that looks to be failing.  Anyone
have any useful tips here?

Cheers,

Brian

--------------------------------------------------------------------------
Brian Larsen
Boston University
Center for Space Physics