program to count commented characters and words in a C file - c

Question

I have to count characters and word in comment of a C file, for both single line comments and blocked comment. Here's what I have:
#include <stdio.h>
#define IN = 1
#define OUT = 0
main() {
int c, nc;
nc = 0;
while ((c = getchar()) != EOF) {
if (c == '/') {
if (getchar() == '/')
while (getchar() != '\n')
++nc;
}
}
if (c == '/') {
if (getchar() == '*')
while (getchar() != '/')
++nc;
}
printf("Character Counts: %d\n", nc);
}
It works for every single line comment (//), but it skips the blocked comments (/*...*/). I feel like it never enter the if block for the blocked comment. Much appreciate!

Answer 1

There are multiple problems in your code:
You must specify int as the return type of the main function. The syntax in the question is obsolete.
The definitions of IN and OUT are incorrect. You should either use
#define IN 1
#define OUT 0
or
enum { IN = 1, OUT = 0 };
The first loop consumes all the bytes in standard input, you are at the end of file, so the tests for /*...*/ comments never produce anything.
loops such as while (getchar() != '\n') can run forever if the byte tested is not found before the end of file.
You cannot test // and /*...*/ comments separately as one can hide the other:
//* this is a line comment that does not start a C style one
/* this comment contains a // but stops here */ return 0;
Note also that you should parse C strings and character constants as they may contain // and or /* sequences that do not start a comment.
For a complete solution, you should also handle escaped newlines. Here are some pathological examples:
// this is a line comment that extends \
on multiple \
lines (and tricks the colorizer)
/\
* this is a C comment, but the colorizer missed it *\
/
This problem is non-trivial to solve in the general case, but you can start with simple cases.
Here is a modified version:
#include <stdio.h>
int main() {
int c, cc, nc = 0;
while ((c = getchar()) != EOF) {
if (c == '/') {
if ((cc = getchar()) == '/') {
while ((c = getchar()) != '\n')
nc++;
} else
if (cc == '*') {
while ((cc = getchar()) != EOF) {
if (cc == '*') {
if ((cc = getchar()) == '/')
break;
ungetc(cc, stdin);
}
nc++;
}
}
}
}
printf("Character Counts: %d\n", nc);
return 0;
}

Answer 2

I added code to count the words. It works on few occasions, but it behaves weird when I have space after the slash. For example, // comment... Most of the time, the word count is off by 1.
#include<stdio.h>
#define IN 1
#define OUT 0
int main() {
int c, cc, nc = 0;
int state;
int nw = 0;
state = OUT;
while ((c = getchar()) != EOF) {
if (c == '/') {
if ((cc = getchar()) == '/') {
while ((c = getchar()) != '\n'){
nc++;
if (c == ' ' || c == '\t')
state = OUT;
else if (state == OUT){
state = IN;
nw++;
}
}
}
else if (cc == '*') {
while ((cc = getchar()) != EOF) {
if (cc == ' ' || cc == '\t')
state = OUT;
else if (state == OUT){
state = IN;
nw++;
}
if (cc == '*') {
if ((cc = getchar()) == '/')
break;
ungetc(cc, stdin);
}
nc++;
}
}
}
}
printf("Character Counts: %d\n", nc);
printf("Word Counts: %d\n", nw);
return 0;
}

Answer 3

program to count commented characters and words in a C file
it skips the blocked comments (/.../)
I recommend, at a minimum, to parse code and look for 5 states: normal, in a // comment, in a /* comment, in a "" string literal, in a '' character constant.
// pseudo code
while ((ch = getchar()) != EOF) {
if ch == '/' and next == '/', process `//` comment until end-of-line
elseif ch '/' and next == '*', process `/*` comment until `*/`
elseif ch '"', process string until " (but not \")
elseif ch ''', process constant until ' (but not \')
else process normally
}
To look at the next character, call getchar() and then ungetc() if not as expected.