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How to search C code for division or sqrt

Date: 2008-07-24  |   Modified: 2008-09-09  |   Tags: c_cplusplus, python, regexes

The following Python script searches through C code for division or sqrt and prints the line of code and the line number. It skips C comments. To use, run python find_divides.py filename.c 

#!/usr/bin/python

"""find_divides.py

usage: python find_divides.py filename
"""

import re
import sys

def main():
    filename = sys.argv[1]
    text = open(filename).read()
    lines = text.splitlines()
    lines = ["%4d: %s" % (i, line) for (i, line) in enumerate(lines)]
    text = "\n".join(lines)
    text = remove_comments_and_strings(text)

    for line in text.splitlines():
        if ("/" in line) or ("sqrt" in line):
            print line

def remove_comments_and_strings(text):
    """ remove c-style comments and strings
        text: blob of text with comments (can include newlines)
        returns: text with comments and strings removed
    """
    pattern = r"""
                            ##  --------- COMMENT ---------
           /\*              ##  Start of /* ... */ comment
           [^*]*\*+         ##  Non-* followed by 1-or-more *'s
           (                ##
             [^/*][^*]*\*+  ##
           )*               ##  0-or-more things which don't start with /
                            ##    but do end with '*'
           /                ##  End of /* ... */ comment
         |                  ##  -OR-  various things which aren't comments:
           (                ## 
                            ##  ------ " ... " STRING ------
             "              ##  Start of " ... " string
             (              ##
               \\.          ##  Escaped char
             |              ##  -OR-
               [^"\\]       ##  Non "\ characters
             )*             ##
             "              ##  End of " ... " string
           |                ##  -OR-
                            ##
                            ##  ------ ' ... ' STRING ------
             '              ##  Start of ' ... ' string
             (              ##
               \\.          ##  Escaped char
             |              ##  -OR-
               [^'\\]       ##  Non '\ characters
             )*             ##
             '              ##  End of ' ... ' string
           |                ##  -OR-
                            ##
                            ##  ------ ANYTHING ELSE -------
             (.              ##  Anything other char
             [^/"'\\]*)      ##  Chars which doesn't start a comment, string
           )                ##    or escape
    """
    regex = re.compile(pattern, re.VERBOSE|re.MULTILINE|re.DOTALL)
    goodstuff = [m.group(5) for m in regex.finditer(text) if m.group(5)]
    return "".join(goodstuff)

if __name__ == "__main__":
    main()

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