JezK
Edit File: ast_transforms.py
#------------------------------------------------------------------------------ # pycparser: ast_transforms.py # # Some utilities used by the parser to create a friendlier AST. # # Copyright (C) 2008-2012, Eli Bendersky # License: BSD #------------------------------------------------------------------------------ from . import c_ast def fix_switch_cases(switch_node): """ The 'case' statements in a 'switch' come out of parsing with one child node, so subsequent statements are just tucked to the parent Compound. Additionally, consecutive (fall-through) case statements come out messy. This is a peculiarity of the C grammar. The following: switch (myvar) { case 10: k = 10; p = k + 1; return 10; case 20: case 30: return 20; default: break; } Creates this tree (pseudo-dump): Switch ID: myvar Compound: Case 10: k = 10 p = k + 1 return 10 Case 20: Case 30: return 20 Default: break The goal of this transform it to fix this mess, turning it into the following: Switch ID: myvar Compound: Case 10: k = 10 p = k + 1 return 10 Case 20: Case 30: return 20 Default: break A fixed AST node is returned. The argument may be modified. """ assert isinstance(switch_node, c_ast.Switch) if not isinstance(switch_node.stmt, c_ast.Compound): return switch_node # The new Compound child for the Switch, which will collect children in the # correct order new_compound = c_ast.Compound([], switch_node.stmt.coord) # The last Case/Default node last_case = None # Goes over the children of the Compound below the Switch, adding them # either directly below new_compound or below the last Case as appropriate for child in switch_node.stmt.block_items: if isinstance(child, (c_ast.Case, c_ast.Default)): # If it's a Case/Default: # 1. Add it to the Compound and mark as "last case" # 2. If its immediate child is also a Case or Default, promote it # to a sibling. new_compound.block_items.append(child) _extract_nested_case(child, new_compound.block_items) last_case = new_compound.block_items[-1] else: # Other statements are added as childrent to the last case, if it # exists. if last_case is None: new_compound.block_items.append(child) else: last_case.stmts.append(child) switch_node.stmt = new_compound return switch_node def _extract_nested_case(case_node, stmts_list): """ Recursively extract consecutive Case statements that are made nested by the parser and add them to the stmts_list. """ if isinstance(case_node.stmts[0], (c_ast.Case, c_ast.Default)): stmts_list.append(case_node.stmts.pop()) _extract_nested_case(stmts_list[-1], stmts_list)