appro> > The function pointer *must* be inside a data object to make
appro> > such constructs legal,
appro> But that's what Richard (subconsciously?) attempted to do in
appro> first place:
Don't look at me, that part of the code was there in mem.c since
eons...
appro> static void (*mem_cb)()=NULL;
appro>
appro> void CRYPTO_mem_leaks_cb(void (*cb)())
appro> {
appro> ...
appro> mem_cb=cb;
appro> lh_doall_arg(mh,(void (*)())cb_leak,(char *)mem_cb);
appro> mem_cb=NULL;
appro> ...
appro> }
appro>
appro> I mean someting has prevented him from just "lh_doall_arg(mh,(void
appro> (*)())cb_leak,(char *)cb)," hasn't it?
I Actually don't know why Eric needed to do that. But just for
clarity, let me show you what DEC C says:
void (*mem_callback)()=(void (*)())cb;
...........................................^
%CC-I-NONSTANDCAST, In the initializer for mem_callback, "cb" of type "pointer to
char", is being converted to "pointer to function () returning void". Such a cast is
not permitted by the standard.
at line number 668 in file
DISK$ALPUTILS:[LEVITTE.WRK.OPENSSL-0_9_5-DEV.CRYPTO]MEM_DBG.C;3
lh_doall_arg(mh,(void (*)())cb_leak,(char *)mem_cb);
....................................................^
%CC-I-NONSTANDCAST, In this statement, "mem_cb" of type "pointer to function ()
returning void", is being converted to "pointer to char". Such a cast is not
permitted by the standard.
at line number 677 in file
DISK$ALPUTILS:[LEVITTE.WRK.OPENSSL-0_9_5-DEV.CRYPTO]MEM_DBG.C;3
As you can see, whatever you do with the current scheme, there will
always be a conversion between function pointers and non-function
pointers.
appro> > so this is not silly at all. An alternative would be to use
appro> > unions of a function pointer
appro> Why structures/unions? "lh_doall_arg(mh,(void (*)())cb_leak,(void
appro> *)&mem_cb)" should do...
The easiest way to avoid the conversions noted above is to have a
union like this:
union foo {
void *simple;
int (*fn)();
};
and use it internally. You put whatever char * you want to convert to
a functino pointer into simple and pull out the function pointer from
fn, and vice versa.
appro> Of course provided that it's appropriately derefenced in
appro> cb_leak!
As you can see above, that's exactly one of the problems.
appro> And I fail to understand why mem_cb has to be declared static?
Not to be seen outside of the file?
appro> It can be perfectly declared in CRYPTO_mem_leaks_cb scope which
appro> also makes it multi-thead safe, doesn't it?
You're absolutely right about, but that is beside the point in this
case. This is a ANSI C problem, not a MT problem.
appro> typedef void (*cb_t) ();
appro>
appro> static void cb_leak(MEM *m, void *cb)
appro> {
appro> void (*mem_callback)()=*((cb_t *)cb);
You convert from void * to void (*)() (i.e. between a "simple
type" and a function pointer). DEC C will complain.
appro> mem_callback(m->order,m->file,m->line,m->num,m->addr);
appro> }
appro>
appro> void CRYPTO_mem_leaks_cb(void (*cb)())
appro> {
appro> void (*mem_cb)() = cb;
appro> if (mh == NULL) return;
appro> CRYPTO_w_lock(CRYPTO_LOCK_MALLOC2);
appro> lh_doall_arg(mh,(void (*)())cb_leak,(void *)(&mem_cb));
You convert from void (*)() to void * (i.e. between a "simple
type" and a function pointer). DEC C will complain.
appro> CRYPTO_w_unlock(CRYPTO_LOCK_MALLOC2);
appro> }
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