pycparser 嵌套节点访问者

Question

我正在尝试使用带有访问者的 pycparser 为每个 IF 语句解析 C 代码。根据我的观察，它只访问没有嵌套 IF 的顶级节点。是故意的，还是我的代码有问题？

Answer 1

查看 class 的评论：https://github.com/eliben/pycparser/blob/master/pycparser/c_ast.py#L107

The children of nodes for which a visit_XXX was defined will not be visited - if you need this, call generic_visit() on the node.

You can use:

NodeVisitor.generic_visit(self, node)

我试过了，它对我有用：

if_conditions.py

from __future__ import print_function
import sys

# This is not required if you've installed pycparser into
# your site-packages/ with setup.py
sys.path.extend(['.', '..'])

from pycparser import c_parser, c_ast, parse_file

class IfVisitor(c_ast.NodeVisitor):
    def __init__(self):
        pass

    def visit_If(self, node):
        node.show()
        self.generic_visit(node);



def start(filename):
    ast = parse_file(filename, use_cpp=True)
    v = IfVisitor()
    v.visit(ast)


if __name__ == "__main__":
    if len(sys.argv) > 2:
        filename = sys.argv[1]
    else:
        filename = 'examples/c_files/test.c'

    start(filename)

test.c

main ( int arc, char **argv ) {

    int i = 1;

    if (i > 1) {
        if (i > 2) {
            printf("Yay!");
        }
    }

    // code
    return 0; // Indicates that everything vent well.     
}

Answer 2

generic_visit() 就可以了。或者，只是 re-visit 个子节点。

https://github.com/eliben/pycparser/blob/master/examples/func_calls.py#L29

# A visitor with some state information (the funcname it's looking for)
class FuncCallVisitor(c_ast.NodeVisitor):
    def __init__(self, funcname):
        self.funcname = funcname

    def visit_FuncCall(self, node):
        if node.name.name == self.funcname:
            print('%s called at %s' % (self.funcname, node.name.coord))
        # Visit args in case they contain more func calls.
        if node.args:
            self.visit(node.args)

在这种情况下（IF 语句），

if node.iftrue:
    self.visit(node.iftrue)

if node.iffalse:
    self.visit(node.iffalse)

pycparser 嵌套节点访问者

pycparser nested node visitor

c

python

pycparser