Andy Polyakov <[EMAIL PROTECTED]>:
>> The function pointer *must* be inside a data object to make such constructs
>> legal,
> But that's what Richard (subconsciously?) attempted to do in first
> place:
>
> static void (*mem_cb)()=NULL;
>
> void CRYPTO_mem_leaks_cb(void (*cb)())
> {
> ...
> mem_cb=cb;
> lh_doall_arg(mh,(void (*)())cb_leak,(char *)mem_cb);
> mem_cb=NULL;
> ...
> }
That's weird, I did not notice this and don't know why he did it this way
(and probably he doesn't either :-).
This is however not what I meant, this is just like calling
lh_doall_arg(mh,(void (*)())cb_leak,(char *)cb);
without using the extra static variable. We're still passing
a function pointer value. What would work, however, is
> void CRYPTO_mem_leaks_cb(void (*cb)())
> {
> ...
> void *cb_ptr=&cb;
> lh_doall_arg(mh,(void (*)())cb_leak,cb);
> ...
> }
(there's no reason to introduce a struct unless one wants to do things
over-complicated, I don't know why I mentioned structs before).
The point is that C doesn't like mixing function pointers and data
object pointers; they don't necessarily have identical
representations (you could have 32 bit function pointers, but 64
bit data pointers). To force C to convert values between these types,
you'd have to cast to some integer type inbetween:
(void (*)()) (long) cb
But of course this is so complicated because it should never be done
and is not guaranteed to do anything useful. &cb, on the other hand,
is the pointer to some data object; the function that gets this
pointer as an argument has to retrieve the actual function pointer
from inside this data object, i.e. use *((void (**)()) arg)
where arg is the void * argument passed to it.
______________________________________________________________________
OpenSSL Project http://www.openssl.org
Development Mailing List [EMAIL PROTECTED]
Automated List Manager [EMAIL PROTECTED]
