The exception mechanism assumes that exceptions from DO_FCALL are
already happening after the function call. This means that we are
currently leaking the passed arguments, and I think we can also
corrupt the VM stack due to incorrect frame linking in some cases
(there are assertion failures if the VM stack page size is reduced).
Instead handle the stack frame freeing manually for this special
case.
By avoiding unused variable opline warnings. Also clean up the
replacement of ZEND_VM_SPEC -- we were sometimes treating it as
an always-defined constant with a value (what it actually is) and
sometimes as a conditionally defined constant (which it isn't, but
which still worked thanks to the specializer). Switch to only
treating it as a constant with a value.
No notice is thrown for list() accesses, because we did not come
to an agreement regarding patterns like
while ([$key, $value] = yield $it->next()) { ... }
where silent null access may be desirable.
No effort is made to suppress multiple notices in access chains
likes $x[0][0][0], because the technical complexity this causes
does not seem worthwhile.
RFC: https://wiki.php.net/rfc/notice-for-non-valid-array-container
symtable_cache_ptr now points to the first unused symtable_cache
entry, rahter than the last used one. This avoids taking a pointer
to the minus first element of the array, which is UB. Instead we
take a pointer to the end plus one, which is not UB.
RFC: https://wiki.php.net/rfc/tostring_exceptions
And convert some object to string conversion related recoverable
fatal errors into Error exceptions.
Improve exception safety of internal code performing string
conversions.
Ensure that the "creating default object from empty value" warning is
always thrown. Previously some cases were missing the warning, in
particular those going through FETCH_OBJ_W rather than a dedicated
opcode (like ASSIGN_OBJ).
One slightly unfortunate side-effect of this change is that something
like $a->b->c = 'd' will now generate two warnings rather than one
when $a is null (one for property b, one for property c).
