[clean-list] Calling C with side effects

[Matthew Bromberg]

I am testing the FFI and am attempting to call C with some side affects
using the technique shown in one of the htoclean examples. I am running 
windows XP 64, but all the
code is 32 bit of course.

Unfortunately I can not get the side effect to manifest, even though (I 
think)
the C function gets called.

Here is the clean code:
module matrix
import StdEnv
import StdList
import StdArray

rmac :: !Real !{#Real} !{#Real} -> Int;
rmac a0 a1 a2 = code {
    ccall rmac "RAA:I"
}

x :: {#Real}
x = {0.5, -0.5, 1.0, -1.0}

// unboxed array IO, uniqueness

y :: *{#Real}
y = {1.0, 2.0, 3.0, 4.0}

nlen :: *Int
nlen = 0

Start :: (*{#Real}, Int)
Start
#! nlen = rmac  2.0 x  y
= (y, nlen)

This code outputs
({1,2,3,4},4)
Thus y has not changed and the side effect I was looking for in rmac did 
not occur even though nlen is
correctly altered!.  Yet it seems a very similar technique is applied in 
the example_string1  example in htoclean.

Here is the C code for rmac
#include "acml.h"
#include "Clean.h"
#include "cmatrix.h"
#include "stdio.h"

/* real multiply and accumulate using a stride of 1
 * y = y + alpha * x
 * the array length is returned */
int rmac(double alpha, CleanRealArray x,  CleanRealArray y )
{
int nlen ;
int k ;
nlen = CleanRealArraySize(y);
for (k = 0 ; k < nlen ; k++) {
        y[k]  = y[k] + alpha * x[k] ;
        // printf("y[%d]: %g\n", k, y[k]) ;
}
 // daxpy(nlen, alpha, x, 1, y, 1) ;
return(nlen) ;
}


By the way, I compile this to a .dll, create a symbol file and then link 
the dll in.  If I attempt to link in routines from other dlls  I always 
get into trouble, either it can't find them or the link creates an 
unusable binary. ie if I uncomment the printf statement, the linker can 
not find printf even though the system libraries should all be on the 
path; or if I try to link in daxpy from the acml BLAS library I get a 
binary that fails to launch.  The linker seems to have some issues with 
dynamic link libraries and unfortunately it doesn't support static 
libraries. I assume I'm just doing something wrong, since obviously the 
gui libraries are hooking into a bunch of windows .dlls.