----- Message d'origine ----
> De : Paolo Bonzini <bonz...@gnu.org>
> À : Mathieu Suen <mathieus...@yahoo.fr>
> Cc : help-smalltalk@gnu.org
> Envoyé le : Mar 22 février 2011, 16h 52min 43s
> Objet : Re: [Help-smalltalk] c-call-out and c-call-in with struct.
>
> On 02/22/2011 03:47 PM, Mathieu Suen wrote:
> > I have a quick look at ffi to see if pass-by-value of a struct (with a size
> > greater than 8bit) was available
>
> How do you do that? (Serious question, I'm busy so I'm not looking it up
>right now).
I have made a small test:
#include <stdlib.h>
#include <ffi.h>
#include <stdio.h>
typedef struct rect {
double f;
double g;
double h;
} rect;
void
foo (rect argStruct)
{
printf ("Receive a strcut by value f=%f, g=%f, h=%f\n", argStruct.f,
argStruct.g, argStruct.h);
}
int
main ()
{
int i;
ffi_cif cif;
ffi_type * arg[1];
ffi_type structType;
ffi_type * element[4];
void * value[1];
rect aStruct;
arg[0] = &structType;
structType.size = 0;
structType.alignment = 0;
value[0] = (void*)&aStruct;
for (i = 0; i < 3; i++)
element[i] = &ffi_type_double;
element[3] = NULL;
structType.elements = &element;
if (ffi_prep_cif (&cif, FFI_DEFAULT_ABI, 1, &ffi_type_void, arg) == FFI_OK)
{
aStruct.g = 5.5;
aStruct.h = 3.4;
aStruct.f = 9.0;
ffi_call (&cif, foo, NULL, value);
}
else
{
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
So for example all you have to do is to declare the struct like this:
ffi_type structType;
ffi_type * element[4];
for (i = 0; i < 3; i++)
element[i] = &ffi_type_double;
element[3] = NULL;
structType.elements = &element;
>
> > Now in gst everything is bound to a cparam so that is going to make a lot
of
> > refactoring in other to have c struct pass-by-value.
>
> This may or may not be true depending on the answer to question 1...
>
> Paolo
>
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