finding a function name and counting its LOC

Question

So you know off the bat, this is a project I've been assigned. I'm not looking for an answer in code, but more a direction.

What I've been told to do is go through a file and count the actual lines of code while at the same time recording the function names and individual lines of code for the functions. The problem I am having is determining a way when reading from the file to determine if the line is the start of a function.

So far, I can only think of maybe having a string array of data types (int, double, char, etc), search for that in the line and then search for the parenthesis, and then search for the absence of the semicolon (so i know it isn't just the declaration of the function).

So my question is, is this how I should go about this, or are there other methods in which you would recommend?

The code in which I will be counting will be in C++.

Answer 1

Three approaches come to mind.

1. Use regular expressions. This is fairly similar to what you're thinking of. Look for lines that look like function definitions. This is fairly quick to do, but can go wrong in many ways.

   char *s = "int main() {"
   

   is not a function definition, but sure looks like one.

   char
   * /* eh? */
   s
   (
   int /* comment? // */ a
   )
   // hello, world /* of confusion
   {
   

   is a function definition, but doesn't look like one.

   Good: quick to write, can work even in the face of syntax errors; bad: can easily misfire on things that look like (or fail to look like) the "normal" case.

   Variant: First run the code through, e.g., GNU indent. This will take care of some (but not all) of the misfires.

2. Use a proper lexer and parser. This is a much more thorough approach, but you may be able to re-use an open source lexer/parsed (e.g., from gcc).

   Good: Will be 100% accurate (will never misfire). Bad: One missing semicolon and it spews errors.

3. See if your compiler has some debug output that might help. This is a variant of (2), but using your compiler's lexer/parser instead of your own.