徐迪 <xudifsd@xxxxxxxxx> writes:
> The sigchain APIs require user to code like:
>
> void clean_foo_on_signal(int sig)
> {
> clean_foo();
> sigchain_pop(sig);
> raise(sig);
> }
I can see the repetition, but I do not think your macro is a very good way
to reduce it. Can't we fix the sigchain API a bit, perhaps first by
making a bit more state available to the sigchain stack?
typedef void (*sigchain_fn)(int, void *);
int sigchain_push(int sig, sigchain_fn fn, void *cb_data);
int sigchain_pop(int sig);
void sigchain_push_common(sigchain_fn fn, void *cb_data);
And then make the repetitive one into a single copy of a helper function,
while giving a new external interface to register a on_signal handler:
static void relay_fn(int sig, void *cb_data)
{
void (*fn)(void) = cb_data; /* [*1*] */
fn();
sigchain_pop(sig);
raise(sig);
}
void sigchain_add_relayed(void (*fn)(void))
{
sigchain_push_common(relay_fn, fn);
}
The code that wants to register a clean-up action would do:
sigchain_add_relayed(clean_foo);
instead of
sigchain_push_common(clean_foo_on_signal);
with repeated definition of clean_xxx_on_signal.
Hmm?
[Footnote]
*1* Yes, I know, this casts between a data pointer and a function pointer
that is not portable, but the purpose of this pseudo-code is primarily to
illustrate the high level view of the idea. We would probably want to be
able to pass callback value to the clean_foo() function and at that point,
we would likely to be passing a pointer to a struct, and we could declare
the first element of such a struct is a pointer to a sigchain_fn, or
something.
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