test@localhost ~/pycparser-1.07 $ cat rofl.c 
#include<stdio.h>  #define __(a) goto a; #define ___(a) putchar(a); #define _(a,b) ___(a) __(b); main() { _:__(t)a:_('r',g)b:_('$',p) c:_('l',f)d:_(' ',s)e:_('a',s) f:_('o',q)g:_('l',h)h:_('d',n) i:_('e',w)j:_('e',x)k:_('\n',z) l:_('H',l)m:_('X',i)n:_('!',k) o:_('z',q)p:_('q',b)q:_(',',d) r:_('i',l)s:_('w',v)t:_('H',j) u:_('a',a)v:_('o',a)w:_(')',k) x:_('l',c)y:_('\t',g)z:___(0x0)}
test@localhost ~/pycparser-1.07 $ vi rofl.c 
test@localhost ~/pycparser-1.07 $ cat rofl.c 
#include<stdio.h>
#define __(a) goto a;
#define ___(a) putchar(a);
#define _(a,b) ___(a) __(b);
main() { _:__(t)a:_('r',g)b:_('$',p) c:_('l',f)d:_(' ',s)e:_('a',s) f:_('o',q)g:_('l',h)h:_('d',n) i:_('e',w)j:_('e',x)k:_('\n',z) l:_('H',l)m:_('X',i)n:_('!',k) o:_('z',q)p:_('q',b)q:_(',',d) r:_('i',l)s:_('w',v)t:_('H',j) u:_('a',a)v:_('o',a)w:_(')',k) x:_('l',c)y:_('\t',g)z:___(0x0)}
test@localhost ~/pycparser-1.07 $ gcc -E rofl.c > processed.c 
test@localhost ~/pycparser-1.07 $ head -n 2 processed.c 
# 1 "rofl.c"
# 1 "<built-in>"
test@localhost ~/pycparser-1.07 $ tail -n 2 processed.c 

main() { _:goto t;a:putchar('r'); goto g;;b:putchar('$'); goto p;; c:putchar('l'); goto f;;d:putchar(' '); goto s;;e:putchar('a'); goto s;; f:putchar('o'); goto q;;g:putchar('l'); goto h;;h:putchar('d'); goto n;; i:putchar('e'); goto w;;j:putchar('e'); goto x;;k:putchar('\n'); goto z;; l:putchar('H'); goto l;;m:putchar('X'); goto i;;n:putchar('!'); goto k;; o:putchar('z'); goto q;;p:putchar('q'); goto b;;q:putchar(','); goto d;; r:putchar('i'); goto l;;s:putchar('w'); goto v;;t:putchar('H'); goto j;; u:putchar('a'); goto a;;v:putchar('o'); goto a;;w:putchar(')'); goto k;; x:putchar('l'); goto c;;y:putchar('\t'); goto g;;z:putchar(0x0);}
test@localhost ~/pycparser-1.07 $ tail -n 1 processed.c > wat
test@localhost ~/pycparser-1.07 $ mv wat processed.c 
test@localhost ~/pycparser-1.07 $ cat processed.c 
main() { _:goto t;a:putchar('r'); goto g;;b:putchar('$'); goto p;; c:putchar('l'); goto f;;d:putchar(' '); goto s;;e:putchar('a'); goto s;; f:putchar('o'); goto q;;g:putchar('l'); goto h;;h:putchar('d'); goto n;; i:putchar('e'); goto w;;j:putchar('e'); goto x;;k:putchar('\n'); goto z;; l:putchar('H'); goto l;;m:putchar('X'); goto i;;n:putchar('!'); goto k;; o:putchar('z'); goto q;;p:putchar('q'); goto b;;q:putchar(','); goto d;; r:putchar('i'); goto l;;s:putchar('w'); goto v;;t:putchar('H'); goto j;; u:putchar('a'); goto a;;v:putchar('o'); goto a;;w:putchar(')'); goto k;; x:putchar('l'); goto c;;y:putchar('\t'); goto g;;z:putchar(0x0);}
test@localhost ~/pycparser-1.07 $ cat lolz.py 
from pycparser import CParser
from pycparser.c_ast import Goto, Label, FuncCall

if __name__ == '__main__':
    with open('processed.c') as f:
        source = f.read()
    tree = CParser().parse(source)
    main = tree.children()[0]
    compound = main.children()[1]

    first = compound.children()[0]
    assert isinstance(first, Label)
    assert len(first.children()) == 1
    first_goto = first.children()[0]
    assert isinstance(first_goto, Goto)

    goto = first_goto.name

    output = []
    children = compound.children()
    while True:
        for (i, child) in enumerate(children):
            if isinstance(child, Label) and child.name == goto:
                break
        else:
            assert False, "couldn't find label to jump to"
        func = child.stmt
        assert isinstance(func, FuncCall)
        func_id = func.children()[0]
        assert func_id.name == 'putchar'
        args = func.args
        assert len(args.exprs) == 1
        arg = args.exprs[0]
        if arg.type == 'int':
            assert arg.value == '0x0' # wtf...
            output.append(chr(int(arg.value, 16)))
        else:
            assert arg.type == 'char'
            output.append(arg.value[1:-1])
        try:
            goto = children[i + 1]
        except IndexError:
            break
        assert isinstance(goto, Goto)
        goto = goto.name
    print 'program will output the following:'
    print repr(''.join(output))
test@localhost ~/pycparser-1.07 $ python lolz.py 
program will output the following:
'Hello, world!\\n\x00'