Possible to exclude comments from textwidth?

Question

I recently discovered the textwidth setting, which lets me configure vim to insert a "smart" whitespace-delimited carriage return as I'm typing when my line of text exceeds my specified limit.

Is there a way I can have this feature only apply when I'm typing in a non-commented block of text?

E.g.:

:set tw=20

:set formatoptions+=t

:set cino=(0

Now as I typed the below, vim auto-inserted the carriage-return and indentation between int and b, which is nice:

  1 int foo( int a, int                                                                                                                                                                                                                                                         
  2          b, int c )   

Is it possible to configure vim to naturally allow lines 4 and 5 below?

  1 int foo( int a, int                                                                                                                                                                                                                                                         
  2          b, int c )                                                                                                                                                                                                                                                          
  3 {                                                                                                                                                                                                                                                                           
  4   /* Can vim be made to allow this line even when textwidth is set to 20? */                                                                                                                                                                                                
  5   int i = 5; // Can vim also be made to allow this line even when textwidth is set to 20?                                                                                                                                                                                   
  6   return i;
  7 }                                                                                                                                                                                                                                                                           

I am specifically wondering whether the above "exceptions" to line-breaking can be done "as I type" as opposed to applying a formatting after text has been typed.

UPDATE: What I have tried:

I tried adapting an answer to this question by adding the following to my .vimrc:

augroup filetypes
  autocmd!

  autocmd FileType c call s:fubar()
augroup end

" Set up ft=c
fun! s:fubar()
  augroup ft_c
    autocmd!
    autocmd CursorMoved,CursorMovedI *
          \ if index(["cCommentGroup"], synIDattr(synID(line('.'), col('.'), 1), 'name')) >= 0
          \| setlocal textwidth=500
          \| else 
            \| setlocal textwidth=80
            \|endif
  augroup end
endfun

This did not affect runtime editing behavior in any way that I could tell. Following is a .cpp file I created after sourcing my updated .vimrc. textwidth is 80 in this output:

  1 #include <iostream>                                                                                                                                                                                                                                                         
  2                                                                                                                                                                                                                                                                             
  3 int main( int argc, char* argv[], char* envz[] )                                                                                                                                                                                                                            
  4 {                                                                                                                                                                                                                                                                           
  5   std::cout << "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"                                                                                                                                                                                              
  6     << std::endl;                                                                                                                                                                                                                                                           
  7   // This is a test of some funky new autocmd stuff in my .vimrc that makes use                                                                                                                                                                                             
  8   // of syntax information...                                                                                                                                                                                                                                               
  9                                                                                                                                                                                                                                                                             
 10   /* This is a test of some funky new autocmd stuff in my .vimrc that makes use                                                                                                                                                                                             
 11    * of syntax information...                                                                                                                                                                                                                                               
 12    */                                                                                                                                                                                                                                                                       
 13 } 

The code was hard-wrapped desirably, but both C and C++ comments were also hard-wrapped.