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503 lines
17 KiB
Python
503 lines
17 KiB
Python
#------------------------------------------------------------------------------
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# pycparser: c_generator.py
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#
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# C code generator from pycparser AST nodes.
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#
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# Eli Bendersky [https://eli.thegreenplace.net/]
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# License: BSD
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#------------------------------------------------------------------------------
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from . import c_ast
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class CGenerator(object):
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""" Uses the same visitor pattern as c_ast.NodeVisitor, but modified to
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return a value from each visit method, using string accumulation in
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generic_visit.
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"""
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def __init__(self, reduce_parentheses=False):
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""" Constructs C-code generator
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reduce_parentheses:
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if True, eliminates needless parentheses on binary operators
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"""
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# Statements start with indentation of self.indent_level spaces, using
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# the _make_indent method.
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self.indent_level = 0
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self.reduce_parentheses = reduce_parentheses
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def _make_indent(self):
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return ' ' * self.indent_level
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def visit(self, node):
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method = 'visit_' + node.__class__.__name__
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return getattr(self, method, self.generic_visit)(node)
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def generic_visit(self, node):
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if node is None:
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return ''
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else:
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return ''.join(self.visit(c) for c_name, c in node.children())
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def visit_Constant(self, n):
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return n.value
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def visit_ID(self, n):
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return n.name
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def visit_Pragma(self, n):
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ret = '#pragma'
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if n.string:
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ret += ' ' + n.string
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return ret
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def visit_ArrayRef(self, n):
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arrref = self._parenthesize_unless_simple(n.name)
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return arrref + '[' + self.visit(n.subscript) + ']'
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def visit_StructRef(self, n):
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sref = self._parenthesize_unless_simple(n.name)
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return sref + n.type + self.visit(n.field)
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def visit_FuncCall(self, n):
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fref = self._parenthesize_unless_simple(n.name)
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return fref + '(' + self.visit(n.args) + ')'
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def visit_UnaryOp(self, n):
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if n.op == 'sizeof':
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# Always parenthesize the argument of sizeof since it can be
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# a name.
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return 'sizeof(%s)' % self.visit(n.expr)
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else:
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operand = self._parenthesize_unless_simple(n.expr)
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if n.op == 'p++':
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return '%s++' % operand
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elif n.op == 'p--':
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return '%s--' % operand
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else:
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return '%s%s' % (n.op, operand)
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# Precedence map of binary operators:
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precedence_map = {
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# Should be in sync with c_parser.CParser.precedence
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# Higher numbers are stronger binding
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'||': 0, # weakest binding
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'&&': 1,
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'|': 2,
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'^': 3,
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'&': 4,
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'==': 5, '!=': 5,
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'>': 6, '>=': 6, '<': 6, '<=': 6,
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'>>': 7, '<<': 7,
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'+': 8, '-': 8,
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'*': 9, '/': 9, '%': 9 # strongest binding
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}
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def visit_BinaryOp(self, n):
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# Note: all binary operators are left-to-right associative
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#
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# If `n.left.op` has a stronger or equally binding precedence in
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# comparison to `n.op`, no parenthesis are needed for the left:
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# e.g., `(a*b) + c` is equivalent to `a*b + c`, as well as
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# `(a+b) - c` is equivalent to `a+b - c` (same precedence).
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# If the left operator is weaker binding than the current, then
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# parentheses are necessary:
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# e.g., `(a+b) * c` is NOT equivalent to `a+b * c`.
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lval_str = self._parenthesize_if(
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n.left,
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lambda d: not (self._is_simple_node(d) or
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self.reduce_parentheses and isinstance(d, c_ast.BinaryOp) and
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self.precedence_map[d.op] >= self.precedence_map[n.op]))
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# If `n.right.op` has a stronger -but not equal- binding precedence,
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# parenthesis can be omitted on the right:
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# e.g., `a + (b*c)` is equivalent to `a + b*c`.
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# If the right operator is weaker or equally binding, then parentheses
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# are necessary:
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# e.g., `a * (b+c)` is NOT equivalent to `a * b+c` and
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# `a - (b+c)` is NOT equivalent to `a - b+c` (same precedence).
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rval_str = self._parenthesize_if(
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n.right,
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lambda d: not (self._is_simple_node(d) or
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self.reduce_parentheses and isinstance(d, c_ast.BinaryOp) and
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self.precedence_map[d.op] > self.precedence_map[n.op]))
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return '%s %s %s' % (lval_str, n.op, rval_str)
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def visit_Assignment(self, n):
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rval_str = self._parenthesize_if(
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n.rvalue,
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lambda n: isinstance(n, c_ast.Assignment))
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return '%s %s %s' % (self.visit(n.lvalue), n.op, rval_str)
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def visit_IdentifierType(self, n):
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return ' '.join(n.names)
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def _visit_expr(self, n):
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if isinstance(n, c_ast.InitList):
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return '{' + self.visit(n) + '}'
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elif isinstance(n, (c_ast.ExprList, c_ast.Compound)):
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return '(' + self.visit(n) + ')'
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else:
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return self.visit(n)
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def visit_Decl(self, n, no_type=False):
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# no_type is used when a Decl is part of a DeclList, where the type is
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# explicitly only for the first declaration in a list.
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#
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s = n.name if no_type else self._generate_decl(n)
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if n.bitsize: s += ' : ' + self.visit(n.bitsize)
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if n.init:
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s += ' = ' + self._visit_expr(n.init)
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return s
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def visit_DeclList(self, n):
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s = self.visit(n.decls[0])
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if len(n.decls) > 1:
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s += ', ' + ', '.join(self.visit_Decl(decl, no_type=True)
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for decl in n.decls[1:])
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return s
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def visit_Typedef(self, n):
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s = ''
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if n.storage: s += ' '.join(n.storage) + ' '
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s += self._generate_type(n.type)
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return s
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def visit_Cast(self, n):
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s = '(' + self._generate_type(n.to_type, emit_declname=False) + ')'
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return s + ' ' + self._parenthesize_unless_simple(n.expr)
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def visit_ExprList(self, n):
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visited_subexprs = []
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for expr in n.exprs:
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visited_subexprs.append(self._visit_expr(expr))
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return ', '.join(visited_subexprs)
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def visit_InitList(self, n):
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visited_subexprs = []
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for expr in n.exprs:
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visited_subexprs.append(self._visit_expr(expr))
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return ', '.join(visited_subexprs)
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def visit_Enum(self, n):
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return self._generate_struct_union_enum(n, name='enum')
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def visit_Alignas(self, n):
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return '_Alignas({})'.format(self.visit(n.alignment))
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def visit_Enumerator(self, n):
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if not n.value:
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return '{indent}{name},\n'.format(
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indent=self._make_indent(),
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name=n.name,
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)
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else:
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return '{indent}{name} = {value},\n'.format(
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indent=self._make_indent(),
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name=n.name,
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value=self.visit(n.value),
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)
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def visit_FuncDef(self, n):
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decl = self.visit(n.decl)
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self.indent_level = 0
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body = self.visit(n.body)
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if n.param_decls:
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knrdecls = ';\n'.join(self.visit(p) for p in n.param_decls)
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return decl + '\n' + knrdecls + ';\n' + body + '\n'
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else:
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return decl + '\n' + body + '\n'
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def visit_FileAST(self, n):
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s = ''
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for ext in n.ext:
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if isinstance(ext, c_ast.FuncDef):
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s += self.visit(ext)
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elif isinstance(ext, c_ast.Pragma):
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s += self.visit(ext) + '\n'
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else:
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s += self.visit(ext) + ';\n'
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return s
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def visit_Compound(self, n):
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s = self._make_indent() + '{\n'
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self.indent_level += 2
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if n.block_items:
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s += ''.join(self._generate_stmt(stmt) for stmt in n.block_items)
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self.indent_level -= 2
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s += self._make_indent() + '}\n'
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return s
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def visit_CompoundLiteral(self, n):
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return '(' + self.visit(n.type) + '){' + self.visit(n.init) + '}'
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def visit_EmptyStatement(self, n):
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return ';'
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def visit_ParamList(self, n):
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return ', '.join(self.visit(param) for param in n.params)
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def visit_Return(self, n):
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s = 'return'
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if n.expr: s += ' ' + self.visit(n.expr)
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return s + ';'
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def visit_Break(self, n):
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return 'break;'
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def visit_Continue(self, n):
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return 'continue;'
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def visit_TernaryOp(self, n):
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s = '(' + self._visit_expr(n.cond) + ') ? '
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s += '(' + self._visit_expr(n.iftrue) + ') : '
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s += '(' + self._visit_expr(n.iffalse) + ')'
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return s
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def visit_If(self, n):
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s = 'if ('
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if n.cond: s += self.visit(n.cond)
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s += ')\n'
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s += self._generate_stmt(n.iftrue, add_indent=True)
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if n.iffalse:
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s += self._make_indent() + 'else\n'
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s += self._generate_stmt(n.iffalse, add_indent=True)
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return s
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def visit_For(self, n):
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s = 'for ('
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if n.init: s += self.visit(n.init)
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s += ';'
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if n.cond: s += ' ' + self.visit(n.cond)
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s += ';'
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if n.next: s += ' ' + self.visit(n.next)
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s += ')\n'
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s += self._generate_stmt(n.stmt, add_indent=True)
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return s
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def visit_While(self, n):
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s = 'while ('
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if n.cond: s += self.visit(n.cond)
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s += ')\n'
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s += self._generate_stmt(n.stmt, add_indent=True)
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return s
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def visit_DoWhile(self, n):
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s = 'do\n'
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s += self._generate_stmt(n.stmt, add_indent=True)
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s += self._make_indent() + 'while ('
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if n.cond: s += self.visit(n.cond)
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s += ');'
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return s
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def visit_StaticAssert(self, n):
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s = '_Static_assert('
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s += self.visit(n.cond)
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if n.message:
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s += ','
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s += self.visit(n.message)
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s += ')'
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return s
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def visit_Switch(self, n):
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s = 'switch (' + self.visit(n.cond) + ')\n'
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s += self._generate_stmt(n.stmt, add_indent=True)
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return s
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def visit_Case(self, n):
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s = 'case ' + self.visit(n.expr) + ':\n'
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for stmt in n.stmts:
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s += self._generate_stmt(stmt, add_indent=True)
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return s
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def visit_Default(self, n):
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s = 'default:\n'
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for stmt in n.stmts:
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s += self._generate_stmt(stmt, add_indent=True)
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return s
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def visit_Label(self, n):
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return n.name + ':\n' + self._generate_stmt(n.stmt)
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def visit_Goto(self, n):
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return 'goto ' + n.name + ';'
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def visit_EllipsisParam(self, n):
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return '...'
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def visit_Struct(self, n):
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return self._generate_struct_union_enum(n, 'struct')
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def visit_Typename(self, n):
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return self._generate_type(n.type)
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def visit_Union(self, n):
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return self._generate_struct_union_enum(n, 'union')
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def visit_NamedInitializer(self, n):
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s = ''
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for name in n.name:
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if isinstance(name, c_ast.ID):
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s += '.' + name.name
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else:
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s += '[' + self.visit(name) + ']'
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s += ' = ' + self._visit_expr(n.expr)
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return s
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def visit_FuncDecl(self, n):
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return self._generate_type(n)
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def visit_ArrayDecl(self, n):
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return self._generate_type(n, emit_declname=False)
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def visit_TypeDecl(self, n):
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return self._generate_type(n, emit_declname=False)
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def visit_PtrDecl(self, n):
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return self._generate_type(n, emit_declname=False)
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def _generate_struct_union_enum(self, n, name):
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""" Generates code for structs, unions, and enums. name should be
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'struct', 'union', or 'enum'.
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"""
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if name in ('struct', 'union'):
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members = n.decls
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body_function = self._generate_struct_union_body
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else:
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assert name == 'enum'
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members = None if n.values is None else n.values.enumerators
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body_function = self._generate_enum_body
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s = name + ' ' + (n.name or '')
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if members is not None:
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# None means no members
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# Empty sequence means an empty list of members
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s += '\n'
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s += self._make_indent()
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self.indent_level += 2
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s += '{\n'
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s += body_function(members)
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self.indent_level -= 2
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s += self._make_indent() + '}'
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return s
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def _generate_struct_union_body(self, members):
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return ''.join(self._generate_stmt(decl) for decl in members)
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def _generate_enum_body(self, members):
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# `[:-2] + '\n'` removes the final `,` from the enumerator list
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return ''.join(self.visit(value) for value in members)[:-2] + '\n'
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def _generate_stmt(self, n, add_indent=False):
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""" Generation from a statement node. This method exists as a wrapper
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for individual visit_* methods to handle different treatment of
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some statements in this context.
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"""
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typ = type(n)
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if add_indent: self.indent_level += 2
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indent = self._make_indent()
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if add_indent: self.indent_level -= 2
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if typ in (
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c_ast.Decl, c_ast.Assignment, c_ast.Cast, c_ast.UnaryOp,
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c_ast.BinaryOp, c_ast.TernaryOp, c_ast.FuncCall, c_ast.ArrayRef,
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c_ast.StructRef, c_ast.Constant, c_ast.ID, c_ast.Typedef,
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c_ast.ExprList):
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# These can also appear in an expression context so no semicolon
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# is added to them automatically
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#
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return indent + self.visit(n) + ';\n'
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elif typ in (c_ast.Compound,):
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# No extra indentation required before the opening brace of a
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# compound - because it consists of multiple lines it has to
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# compute its own indentation.
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#
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return self.visit(n)
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elif typ in (c_ast.If,):
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return indent + self.visit(n)
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else:
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return indent + self.visit(n) + '\n'
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def _generate_decl(self, n):
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""" Generation from a Decl node.
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"""
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s = ''
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if n.funcspec: s = ' '.join(n.funcspec) + ' '
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if n.storage: s += ' '.join(n.storage) + ' '
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if n.align: s += self.visit(n.align[0]) + ' '
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s += self._generate_type(n.type)
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return s
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def _generate_type(self, n, modifiers=[], emit_declname = True):
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""" Recursive generation from a type node. n is the type node.
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modifiers collects the PtrDecl, ArrayDecl and FuncDecl modifiers
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encountered on the way down to a TypeDecl, to allow proper
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generation from it.
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"""
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typ = type(n)
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#~ print(n, modifiers)
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if typ == c_ast.TypeDecl:
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s = ''
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if n.quals: s += ' '.join(n.quals) + ' '
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s += self.visit(n.type)
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nstr = n.declname if n.declname and emit_declname else ''
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# Resolve modifiers.
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# Wrap in parens to distinguish pointer to array and pointer to
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# function syntax.
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#
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for i, modifier in enumerate(modifiers):
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if isinstance(modifier, c_ast.ArrayDecl):
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if (i != 0 and
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isinstance(modifiers[i - 1], c_ast.PtrDecl)):
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nstr = '(' + nstr + ')'
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nstr += '['
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if modifier.dim_quals:
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nstr += ' '.join(modifier.dim_quals) + ' '
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nstr += self.visit(modifier.dim) + ']'
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elif isinstance(modifier, c_ast.FuncDecl):
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if (i != 0 and
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isinstance(modifiers[i - 1], c_ast.PtrDecl)):
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nstr = '(' + nstr + ')'
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nstr += '(' + self.visit(modifier.args) + ')'
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elif isinstance(modifier, c_ast.PtrDecl):
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if modifier.quals:
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nstr = '* %s%s' % (' '.join(modifier.quals),
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' ' + nstr if nstr else '')
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else:
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nstr = '*' + nstr
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if nstr: s += ' ' + nstr
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return s
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elif typ == c_ast.Decl:
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return self._generate_decl(n.type)
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elif typ == c_ast.Typename:
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return self._generate_type(n.type, emit_declname = emit_declname)
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elif typ == c_ast.IdentifierType:
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return ' '.join(n.names) + ' '
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elif typ in (c_ast.ArrayDecl, c_ast.PtrDecl, c_ast.FuncDecl):
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return self._generate_type(n.type, modifiers + [n],
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emit_declname = emit_declname)
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else:
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return self.visit(n)
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def _parenthesize_if(self, n, condition):
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""" Visits 'n' and returns its string representation, parenthesized
|
|
if the condition function applied to the node returns True.
|
|
"""
|
|
s = self._visit_expr(n)
|
|
if condition(n):
|
|
return '(' + s + ')'
|
|
else:
|
|
return s
|
|
|
|
def _parenthesize_unless_simple(self, n):
|
|
""" Common use case for _parenthesize_if
|
|
"""
|
|
return self._parenthesize_if(n, lambda d: not self._is_simple_node(d))
|
|
|
|
def _is_simple_node(self, n):
|
|
""" Returns True for nodes that are "simple" - i.e. nodes that always
|
|
have higher precedence than operators.
|
|
"""
|
|
return isinstance(n, (c_ast.Constant, c_ast.ID, c_ast.ArrayRef,
|
|
c_ast.StructRef, c_ast.FuncCall))
|