Yield now is an expression and the return value is the value passed to
$generator->send(). By default (i.e. if ->next() is called) the value is
NULL.
Unlike in Python ->send() can be run without priming the generator with a
->next() call first.
To keep things clean two new functions are introduced:
zend_clean_and_cache_symbol_table(HashTable *symbol_table)
zend_free_compiled_variables(zval ***CVs, int num)
If the generator is closed before it has finished running, it may happen
that some FREE or SWITCH_FREE opcodes haven't been executed and memory is
leaked.
This fixes it by walking the brk_cont_array and manually freeing the
variables.
For generators ZEND_RETURN directly calls ZEND_VM_RETURN(), thus passing
execution back to the caller (zend_generator_resume).
This commit also adds a check that only return; is used in generators and
not return $value;.
Generators need to switch the execute_data very often. If the execute_data
is allocated on the VM stack this operation would require to always copy
the structure (which is quite large). That's why the execution context is
allocated on the heap instead (only for generators obviously).
. zend_function.pass_rest_by_reference is replaced by
ZEND_ACC_PASS_REST_BY_REFERENCE in zend_function.fn_flags
. zend_function.return_reference is replaced by ZEND_ACC_RETURN_REFERENCE
in zend_function.fn_flags
. zend_arg_info.required_num_args removed. it was needed only for internal
functions. Now the first arg_info for internal function (which has special
meaning) is represented by zend_internal_function_info structure.
. zend_op_array.size, size_var, size_literal, current_brk_cont,
backpatch_count moved into CG(context), because they are used only during
compilation.
. zend_op_array.start_op is moved into EG(start_op), because it's used
only for 'interactive' execution of single top-level op-array.
. zend_op_array.done_pass_two is replaced by ZEND_ACC_DONE_PASS_TWO in
zend_op_array.fn_flags.
. op_array.vars array is trimmed (reallocated) during pass_two.
. zend_class_entry.constants_updated is replaced by
ZEND_ACC_CONSTANTS_UPDATED in zend_class_entry.ce_flags
. the size of zend_class_entry is reduced by sharing the same memory space
by different information for internal and user classes.
See zend_class_inttry.info union.
