Python/ceval.c (part 3)

Source:

cpython 3.14 @ ab2d84fe1023/Python/ceval.c ↗

This annotation covers the container-building, iteration, import, and function-creation opcodes. See python_ceval2_detail and python_ceval_c_detail for the eval loop structure and the basic stack/load/store opcodes.

Map

Lines	Symbol	Role
1-300	BINARY_OP	Dispatch all 13 binary/inplace operators
301-600	UNPACK_SEQUENCE, UNPACK_EX	Sequence unpacking
601-900	FOR_ITER, GET_ITER	For loop iteration
901-1200	BUILD_TUPLE, BUILD_LIST, BUILD_SET, BUILD_MAP	Container construction
1201-1500	BUILD_CONST_KEY_MAP, DICT_UPDATE, LIST_APPEND, etc.	Container accumulation
1501-1800	IMPORT_NAME, IMPORT_FROM, IMPORT_STAR	Import opcodes
1801-2100	MAKE_FUNCTION	Create a function object from code
2101-5500	Remaining opcodes	CALL_FUNCTION_EX, LOAD_SUPER_ATTR, match opcodes

Reading

BINARY_OP

BINARY_OP oparg encodes one of 13 operators (ADD, SUBTRACT, MULTIPLY, etc.). The implementation tries the type-specific slot first, then calls the abstract protocol function.

// CPython: Python/ceval.c:1845 BINARY_OP
inst(BINARY_OP, (lhs, rhs -- res)) {
    ...
    assert(NB_ADD <= oparg && oparg <= NB_INPLACE_XOR);
    PyObject *(*binary_op)(PyObject *, PyObject *);
    binary_op = binary_ops[oparg];
    res = binary_op(lhs, rhs);
    ...
}

binary_ops[] is a table of PyNumber_Add, PyNumber_Subtract, etc.

FOR_ITER

// CPython: Python/ceval.c:2590 FOR_ITER
inst(FOR_ITER, (iter -- iter, next)) {
    /* tp_iternext raises StopIteration to signal exhaustion */
    next = (*Py_TYPE(iter)->tp_iternext)(iter);
    if (next == NULL) {
        if (_PyErr_ExceptionMatches(tstate, PyExc_StopIteration)) {
            _PyErr_Clear(tstate);
        } else if (tstate->c_tracefunc != NULL) {
            ...
        }
        JUMPBY(oparg);  /* jump past the loop body */
        DISPATCH();
    }
}

BUILD_MAP and DICT_UPDATE

BUILD_MAP count pops 2*count items from the stack (alternating key, value) and builds a dict. DICT_UPDATE i calls dict.update with the TOS mapping.

MAKE_FUNCTION

// CPython: Python/ceval.c:3890 MAKE_FUNCTION
inst(MAKE_FUNCTION, (codeobj -- func)) {
    PyObject *qualname = PEEK(1);
    func = (PyObject *)PyFunction_New(codeobj, GLOBALS());
    ...
    if (oparg & 0x08) {
        /* has closure */
        func->func_closure = POP();
    }
    if (oparg & 0x04) {
        /* has annotations */
        func->func_annotations = POP();
    }
    if (oparg & 0x02) {
        /* has kwdefaults */
        func->func_kwdefaults = POP();
    }
    if (oparg & 0x01) {
        /* has defaults */
        func->func_defaults = POP();
    }
}

The oparg bitmask indicates which optional components (defaults, kwdefaults, annotations, closure) are on the stack.

IMPORT_NAME

// CPython: Python/ceval.c:3160 IMPORT_NAME
inst(IMPORT_NAME, (level, fromlist -- module)) {
    PyObject *name = GETITEM(names, oparg);
    module = import_name(tstate, frame, name, fromlist, level);
    ...
}

Calls __import__(name, globals, locals, fromlist, level) which resolves to importlib.__import__.

gopy notes

BINARY_OP is handled in vm/eval_gen.go. FOR_ITER and GET_ITER are in vm/eval_simple.go. MAKE_FUNCTION is in vm/eval_call.go and creates a *objects.Function. IMPORT_NAME routes through vm/eval_import.go.