LC

Trace a Function Call Through CPython

hard2/8

Read CPython's longobject.c: How Python Integers Work Understand the GIL and Write a C Extension That Releases It

Language

Compiler

2.0s Limit 256MB

Implementation

Write a C program documenting the Python function call path.

Requirements:

Define structs simulating PyFrameObject and PyObject (simplified)
Show frame creation with fields: f_back, f_code, f_locals, f_stack
Simulate the eval loop with opcodes: LOAD_FAST, CALL_FUNCTION, RETURN_VALUE
Show how arguments move from caller stack to callee locals
Print each stage: opcode dispatch, frame creation, argument binding, return
Include conceptual flow for a simple function call like add(a, b)

Why This Matters

_PyEval_EvalFrameDefault is the real function name in CPython's ceval.c that every single Python call runs through, and CPython 3.11 rewrote this exact frame-creation path to remove heap allocation per call as part of its 'faster CPython' project. Tracing CALL_FUNCTION to RETURN_VALUE by hand is how you understand why Python function calls cost far more than a C function call.

Hints

0 / 3 revealed

Validation Suite

main.c

Workspace 1.0