Even if the fiber function returns by reference, we must return
a value from Fiber::getReturn() to satisfy the function signature.
Fixes oss-fuzz #36417.
As PHP has a minimum memory usage of 2M (size of allocator chunk),
setting a limit below that value is not meaningful and will be
automatically rounded up to the chunk size. Rather than doing this
silently, show the newly introduced error message.
The memory limit had to be increased to 2M for a number of tests.
tests/lang/bug45392 has been marked as XFAIL. This old bugfix is
not working as intended. The memory limit in main's `PG(memory_limit)`
differs from the one in zend_alloc. In zend_alloc the `AG(mm_heap)->limit`
is defined as `max(passed_value, ZEND_MM_CHUNK_SIZE)`. The check made in
an unclean shutdown will never be true unless the memory limit is lower
than ZEND_MM_CHUNK_SIZE, which happened to be the case in the test.
https://bugs.php.net/bug.php?id=45392fcc0fdd125
This makes debug_print_backtrace() use the same formatting as exception
backtraces. The only difference is that the final #{main} is omitted,
because it wouldn't make sense for limited backtraces, and wasn't there
previously either.
This removes switching to main for fatal errors in fibers in favor of catching any zend_bailout in a fiber and calling zend_bailout again after switching to the previous fiber or {main}.
Checking EG(current_exectue_data) throws into the previous fiber instead of triggering a fatal error during shutdown. A fatal error is triggered only if the throwing destroyed fiber was resumed from {main}.
Previously an exception thrown during fiber destruction resulted in a fatal error, but that exception should be able to be caught (unless we’ve entered shutdown, then still use a fatal error so the error is not hidden).
