Parsing struct within struct in C using pycparser?

Question

I have this example c file I want to parse:

StrcutWithinStruct.c
// simple struct within a struct example

struct A {
 int a;
};

struct B {
 A a;
 int b;
};

I'm running pcyparser to parse it, with the following code

exploreStruct.py
#parse StructWithinStruct

from pycparser import parse_file
ast = parse_file(filename='..\StructWithinStruct.c')
ast.show()

As a result, I got the following:

Tracback (most recent call last):
  File "exploreStruct.py", line 3, in <module>
   ast = parse_file(filename='...\StructWithinStruct.c')
  File "D:\...\pycparser\__init__.py", line 93, in parse_file
   return parser.parse(text,filename)
  File "D:\...\pycparser\c_parser.py", line 146, in parse
   debug=debug_level)
  File "D:\...\pycparser\yacc.py", line 331, in parse
   return self.parseropt_notrack(input, lexer, debug, tracking, tokenfunc)
  File "D:\...\pycparser\yacc.py", line 1181, in parseropt_notrack
   tok=call_errorfunc(self.errorfunc, errtoken, self)
  File "D:\...\pycparser\yacc.py", line 193, in call_errorfunc
   r=errorfunc(token)
  File "D:\...\pycparser\c_parser.py", line 1699, in p_error
   column=self.clex.find_tok_column(p)))
  File "D:\...\pycparser\plyparser.py", line 55, in _parse_error
   raise ParseError("%s: %s % (coord, msg))
pycparser.plyparser.ParserError: D:...\StructWithinStruct.c:7:2: Before A

So, is pycparser can handle struct within struct, or not? I thought this is some basic requirement, so I'm pretty sure that the problem lying in my configuration somewhere...

One more thing: I know that pcypareser author, @Eli Bendersky, says that one should use Clang to parse C++, but I will like to know if there's another option nowadays to parse C++ (preferably over Python), and is user-friendly.

Thanks.

CiaPan · Accepted Answer · 2016-07-25 08:30:30Z

4

Your struct declarations are not closed with a semicolon:

Additionally A itself is not a type name in C. In C++ A alone would suffice, but in C you need to add the struct keyword.

struct A {
 int a;
};

struct B {
 struct A a;
 int b;
};

Or, you can declare a synonym with a typedef keyword:

struct A {
 int a;
};

typedef struct A A;

or, shorter:

typedef struct A {
 int a;
} A;

From that point the declaration

A a;

should compile properly.

edited Jul 25, 2016 at 8:30

answered Jul 25, 2016 at 5:36

CiaPan

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2 Comments

Bak Itzik Over a year ago

The semicolon was a typo over here. and existed in the original code. +1 on the difference between C to C++, and I guess that's why I asked about parsing C++ as well... I'm working with C++, but didn't know there's actual difference in the way you declare your structs as a type name...

CiaPan Over a year ago

@BakItzik In C the struct types is a separate space of identifiers, so you must explicitly state is when referring to a type. In C++, however, struct is equivalent to a class, just with the default initial inheritance type private replaced with public. So the type declared with the struct keyword in C++ becomes a globally available type name in the same manner as those declared as class.

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