Use ISEQ_BODY macro to get the rb_iseq_constant_body of the ISeq. Using
this macro will make it easier for us to change the allocation strategy
of rb_iseq_constant_body when using Variable Width Allocation.
In a forked process from a fiber, the fiber becomes the only
fiber, `fiber_switch` does nothing as there is no other fibers,
`rb_fiber_terminate` does not terminate the fiber. In that case,
reaches the end of `fiber_entry` finaly, which is declared as
"COROUTINE" and should never return.
SunC
```
"cont.c", line 24: identifier redeclared: madvise
current : function(pointer to char, unsigned int, int) returning int
previous: function(pointer to void, unsigned int, int) returning int : "/usr/include/sys/mman.h", line 232
```
GCC
```
cont.c:24:12: error: conflicting types for 'madvise'
24 | extern int madvise(caddr_t, size_t, int);
| ^~~~~~~
In file included from cont.c:16:
/usr/include/sys/mman.h:232:12: note: previous declaration of 'madvise' was here
232 | extern int madvise(void *, size_t, int);
| ^~~~~~~
```
On Solaris, madvise(3C) is NOT defined for SUS (XPG4v2) or later,
but MADV_* macros are defined when __EXTENSIONS__ is defined.
This may cause compile error on Solaris 10 with GCC when
"-Werror=implicit-function-declaration" and "-D_XOPEN_SOURCE=600"
are added by configure.
it is more about memory accounting sake. At allocation time,
we make clear we re possibly reusing regions marked as reusable.
Noted also calls might not necessarily succeed at first so we do
only when necessary.
With this patch, TracePoint receives a `:fiber_switch` event for
_almost_ every fiber switch. Previously, it would not be sent when an
exception was going to be raised. Now the event should only be blockable
by an interrupt (including `Thread#raise`) or a fatal error.
Additionally, interrupts will now be checked on the return fiber
_before_ re-raising the terminating unhandled exception. And a fiber
that terminates with an unhandled exception no longer creates a pending
interrupt on its thread. The exception will be raised in the return
fiber the same way as `Fiber#raise`: using `cont.value` with `cont.argc
== -1`
I moved `rb_exc_raise` from `fiber_store` to the end of `fiber_switch`
after _all_ of the other cleanup code: `fiber_stack_release`,
`th->blocking` increment, `RUBY_VM_CHECK_INTS`, and `EXEC_EVENT_HOOK`.
It seems to me that skipping those other cleanup steps may have also
resulted in other bugs.
* Rename `rb_scheduler` to `rb_fiber_scheduler`.
* Use public interface if available.
* Use `rb_check_funcall` where possible.
* Don't use `unblock` unless the fiber was non-blocking.
* Document Fiber's method related to scheduling;
* Extend Fiber's class docs with concepts of non-blocking
fibers;
* Introduce "imaginary" (documentation-only) class
Fiber::SchedulerInterface to properly document how
scheduler's methods should look.