107 lines
3.6 KiB
Python
107 lines
3.6 KiB
Python
|
#------------------------------------------------------------------------------
|
||
|
|
# pycparser: ast_transforms.py
|
||
|
|
#
|
||
|
|
# Some utilities used by the parser to create a friendlier AST.
|
||
|
|
#
|
||
|
|
# Eli Bendersky [https://eli.thegreenplace.net/]
|
||
|
|
# 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 is 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 `switch(cond) {}`, block_items would have been None)
|
||
|
|
for child in (switch_node.stmt.block_items or []):
|
||
|
|
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 children 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)
|
||
|
|
|