Flag heavy types or refcounted smart pointers passed by value. Applies universally -- by-value copies are wasteful regardless of whether the function is in the hotpath list. Sink parameters (those `std::move`'d in the body) are skipped: the by-value + move idiom is correct C++ for a
(func_node, src: bytes, fenced)
| 419 | |
| 420 | |
| 421 | def _parameter_perf_findings(func_node, src: bytes, fenced) -> list: |
| 422 | """Flag heavy types or refcounted smart pointers passed by value. |
| 423 | Applies universally -- by-value copies are wasteful regardless of |
| 424 | whether the function is in the hotpath list. |
| 425 | |
| 426 | Sink parameters (those `std::move`'d in the body) are skipped: the |
| 427 | by-value + move idiom is correct C++ for a function that conditionally |
| 428 | keeps a local copy of the argument.""" |
| 429 | findings: list = [] |
| 430 | decl = func_node.child_by_field_name("declarator") |
| 431 | fdecl = _walk_to_function_declarator(decl) |
| 432 | if fdecl is None: |
| 433 | return findings |
| 434 | params = fdecl.child_by_field_name("parameters") |
| 435 | if params is None: |
| 436 | return findings |
| 437 | sink_params = _sink_param_names(func_node, src) |
| 438 | for param in params.children: |
| 439 | if param.type != "parameter_declaration": |
| 440 | continue |
| 441 | param_type = param.child_by_field_name("type") |
| 442 | param_decl = param.child_by_field_name("declarator") |
| 443 | if param_type is None: |
| 444 | continue |
| 445 | if param_decl is not None and param_decl.type in ( |
| 446 | "pointer_declarator", |
| 447 | "reference_declarator", |
| 448 | "abstract_pointer_declarator", |
| 449 | "abstract_reference_declarator", |
| 450 | "rvalue_reference_declarator", |
| 451 | "abstract_rvalue_reference_declarator", |
| 452 | ): |
| 453 | continue |
| 454 | # Resolve the parameter's identifier name (if it has one) so we |
| 455 | # can suppress sink-param idioms. |
| 456 | pname = None |
| 457 | if param_decl is not None: |
| 458 | cur = param_decl |
| 459 | while cur is not None and cur.type != "identifier": |
| 460 | next_cur = None |
| 461 | for c in cur.children: |
| 462 | if c.type == "identifier": |
| 463 | next_cur = c |
| 464 | break |
| 465 | if next_cur is None: |
| 466 | for c in cur.children: |
| 467 | if hasattr(c, "children") and c.children: |
| 468 | next_cur = c |
| 469 | break |
| 470 | cur = next_cur |
| 471 | if cur is not None and cur.type == "identifier": |
| 472 | pname = _node_text(cur, src) |
| 473 | if pname is not None and pname in sink_params: |
| 474 | continue |
| 475 | type_text = _node_text(param_type, src).strip() |
| 476 | base = type_text |
| 477 | for q in ("const ", "constexpr ", "volatile ", "mutable ", "register "): |
| 478 | while base.startswith(q): |
no test coverage detected