Python - Regexp - Find function names but not function calls

Question

Ok so i have a bunch of C and C++ code which i need to filter through and find function defenitions. I don't know the function type/return value and i don't know the number of parameters etc in the function defenition or function calls.

So far i have:

import re, sys
from os.path import abspath
from os import walk

function = 'msg'
regexp = r"(" + function + ".*[^;]){"

found = False
for root, folders, files in walk('C:\\codepath\\'):
    for filename in files:
        with open(abspath(root + '/' + filename)) as fh:
            data = fh.read()
            result = re.findall(regexp, data)
            if len(result) > 0:
                sys.stdout.write('\n Found function "' + config.function + '" in ' + filename + ':\n\t' + str(result))
                sys.stdout.flush()
    break

This however, produces some unwanted results. The regexp must be fault taulrant for example these combinations:

Finding "msg" defenition but not "msg()" calls in all mutations of say:

void
shapex_msg (struct shaper *s)
{
  msg (M_INFO, "Output Traffic Shaping initialized at %d bytes per second",
       s->bytes_per_second);
}

or

void shapex_msg (struct shaper *s)
{
  msg (M_INFO, "Output Traffic Shaping initialized at %d bytes per second",
       s->bytes_per_second);
}

or

void shapex_msg (struct shaper *s) {
  msg (M_INFO, "Output Traffic Shaping initialized at %d bytes per second",
       s->bytes_per_second);
}

Bakuriu · Accepted Answer · 2013-04-23 14:47:13Z

1

Maybe something like the following regex:

def make_regex(name):
    return re.compile(r'\s*%s\s*\([^;)]*\)\s*\{' % re.escape(name))

Testing your examples:

>>> text = '''
... void
... shapex_msg (struct shaper *s)
... {
...   msg (M_INFO, "Output Traffic Shaping initialized at %d bytes per second",
...        s->bytes_per_second);
... }
... 
... void shapex_msg (struct shaper *s)
... {
...   msg (M_INFO, "Output Traffic Shaping initialized at %d bytes per second",
...        s->bytes_per_second);
... }
... 
... void shapex_msg (struct shaper *s) {
...   msg (M_INFO, "Output Traffic Shaping initialized at %d bytes per second",
...        s->bytes_per_second);
... }'''
>>> shapex_msg = make_regex_for_function('shapex_msg')
>>> shapex_msg.findall(text)
['\nshapex_msg (struct shaper *s)\n{', ' shapex_msg (struct shaper *s)\n{', ' shapex_msg (struct shaper *s) {']

It works only with multiline definitions:

>>> shapex_msg.findall('''int
        shapex_msg      (
int a,
int b
)  

        {'''
['\n   \tshapex_msg   \t(\nint a,\nint b\n)  \n\n\t{']

While, with function calls:

>>> shapex_msg.findall('shapex_msg(1,2,3);')
[]

Just as a note, your regex doesn't work because .* is greedy and thus it wasn't matching the right closing parentheses.

answered Apr 23, 2013 at 14:47

Bakuriu

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2 Comments

Torxed Over a year ago

Your last edit gave me a working copy! Thank you! Ineed the greedy parameter was messing things up.. Been trying so many combinations i couldn't wrap my head around it.. so thank you!

Bakuriu Over a year ago

@Torxed Yes, sorry. When writing it down I forgot to put an * :s

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