On Sat, Mar 1, 2008 at 9:00 AM, Greg Parker <email@hidden> wrote:
libffi is smart enough to know about all of the ABI rules. If your
ffi_types correctly describe the method's parameters, then libffi
will marshal them properly. (If it doesn't, then that's a libffi
bug.)
I don't think libffi does any type promotion.
Indeed not - the sample below prints different results when run on
PPC (including Rosetta) and i386. On PPC, only the promoted version
returns the correct result. On Intel, both of them do. The question
then, becomes - should libffi be handling this difference
transparently?
ffi_call(3) says:
"rvalue must point to storage that is sizeof(long) or larger. For
smaller return value sizes, the ffi_arg or ffi_sarg integral type must
be used to hold the return value."
char returnCharValue;
ffi_call(&cif_nopromote,
(void(*)(void))getCharFunction,
&returnCharValue,
NULL
);
printf("Return value from cif_nopromote is %d.\n",
returnCharValue);
...which means this isn't allowed. In fact, it's probably smashing
memory on your stack.
--
Greg Parker email@hidden Runtime Wrangler
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