codekingpro/portable-devtools

1# ------------------------------------------------------------------------------2# pycparser: ast_transforms.py3#4# Some utilities used by the parser to create a friendlier AST.5#6# Eli Bendersky [https://eli.thegreenplace.net/]7# License: BSD8# ------------------------------------------------------------------------------9 10from typing import Any, List, Tuple, cast11 12from . import c_ast13 14 15def fix_switch_cases(switch_node: c_ast.Switch) -> c_ast.Switch:16    """The 'case' statements in a 'switch' come out of parsing with one17    child node, so subsequent statements are just tucked to the parent18    Compound. Additionally, consecutive (fall-through) case statements19    come out messy. This is a peculiarity of the C grammar. The following:20 21        switch (myvar) {22            case 10:23                k = 10;24                p = k + 1;25                return 10;26            case 20:27            case 30:28                return 20;29            default:30                break;31        }32 33    Creates this tree (pseudo-dump):34 35        Switch36            ID: myvar37            Compound:38                Case 10:39                    k = 1040                p = k + 141                return 1042                Case 20:43                    Case 30:44                        return 2045                Default:46                    break47 48    The goal of this transform is to fix this mess, turning it into the49    following:50 51        Switch52            ID: myvar53            Compound:54                Case 10:55                    k = 1056                    p = k + 157                    return 1058                Case 20:59                Case 30:60                    return 2061                Default:62                    break63 64    A fixed AST node is returned. The argument may be modified.65    """66    assert isinstance(switch_node, c_ast.Switch)67    if not isinstance(switch_node.stmt, c_ast.Compound):68        return switch_node69 70    # The new Compound child for the Switch, which will collect children in the71    # correct order72    new_compound = c_ast.Compound([], switch_node.stmt.coord)73 74    # The last Case/Default node75    last_case: c_ast.Case | c_ast.Default | None = None76 77    # Goes over the children of the Compound below the Switch, adding them78    # either directly below new_compound or below the last Case as appropriate79    # (for `switch(cond) {}`, block_items would have been None)80    for child in switch_node.stmt.block_items or []:81        if isinstance(child, (c_ast.Case, c_ast.Default)):82            # If it's a Case/Default:83            # 1. Add it to the Compound and mark as "last case"84            # 2. If its immediate child is also a Case or Default, promote it85            #    to a sibling.86            new_compound.block_items.append(child)87            _extract_nested_case(child, new_compound.block_items)88            last_case = new_compound.block_items[-1]89        else:90            # Other statements are added as children to the last case, if it91            # exists.92            if last_case is None:93                new_compound.block_items.append(child)94            else:95                last_case.stmts.append(child)96 97    switch_node.stmt = new_compound98    return switch_node99 100 101def _extract_nested_case(102    case_node: c_ast.Case | c_ast.Default, stmts_list: List[c_ast.Node]103) -> None:104    """Recursively extract consecutive Case statements that are made nested105    by the parser and add them to the stmts_list.106    """107    if isinstance(case_node.stmts[0], (c_ast.Case, c_ast.Default)):108        nested = case_node.stmts.pop()109        stmts_list.append(nested)110        _extract_nested_case(cast(Any, nested), stmts_list)111 112 113def fix_atomic_specifiers(114    decl: c_ast.Decl | c_ast.Typedef,115) -> c_ast.Decl | c_ast.Typedef:116    """Atomic specifiers like _Atomic(type) are unusually structured,117    conferring a qualifier upon the contained type.118 119    This function fixes a decl with atomic specifiers to have a sane AST120    structure, by removing spurious Typename->TypeDecl pairs and attaching121    the _Atomic qualifier in the right place.122    """123    # There can be multiple levels of _Atomic in a decl; fix them until a124    # fixed point is reached.125    while True:126        decl, found = _fix_atomic_specifiers_once(decl)127        if not found:128            break129 130    # Make sure to add an _Atomic qual on the topmost decl if needed. Also131    # restore the declname on the innermost TypeDecl (it gets placed in the132    # wrong place during construction).133    typ: Any = decl134    while not isinstance(typ, c_ast.TypeDecl):135        try:136            typ = typ.type137        except AttributeError:138            return decl139    if "_Atomic" in typ.quals and "_Atomic" not in decl.quals:140        decl.quals.append("_Atomic")141    if typ.declname is None:142        typ.declname = decl.name143 144    return decl145 146 147def _fix_atomic_specifiers_once(148    decl: c_ast.Decl | c_ast.Typedef,149) -> Tuple[c_ast.Decl | c_ast.Typedef, bool]:150    """Performs one 'fix' round of atomic specifiers.151    Returns (modified_decl, found) where found is True iff a fix was made.152    """153    parent: Any = decl154    grandparent: Any = None155    node: Any = decl.type156    while node is not None:157        if isinstance(node, c_ast.Typename) and "_Atomic" in node.quals:158            break159        try:160            grandparent = parent161            parent = node162            node = node.type163        except AttributeError:164            # If we've reached a node without a `type` field, it means we won't165            # find what we're looking for at this point; give up the search166            # and return the original decl unmodified.167            return decl, False168 169    assert isinstance(parent, c_ast.TypeDecl)170    assert grandparent is not None171    cast(Any, grandparent).type = node.type172    if "_Atomic" not in node.type.quals:173        node.type.quals.append("_Atomic")174    return decl, True175