Lexing nested comments

I'm working on a lexer for a language that has nested comments ("(*"&"*)")
and nested pragmas ("<*" & "*>"). I understand there is no way to get
flex to properly match nested items? Is there any way to get the contents
of the pragma to the parser intact so I can issue decent warnings?


On the other hand, I've noticed none of gcc's frontends use a flex
based lexer. Do most serious projects end up using a hand written
lexer?


David Starner - dstarner98@aasaa.ofe.org
web, ftp: x8b4e53cd.dhcp.okstate.edu
[It's easy to get lex to match nested comments, you just can't do it solely
with regular expressions. Here's a sketch:


%x COMMENT
  int nesting = 0;
%%
...
"(*" { BEGIN COMMENT; nesting = 0; /* initialized saved string */ }
<COMMENT>"(*" { /* add to saved string for parser */ nesting++; }
<COMMENT>"*)" { if(--nesting <=0 ) {
BEGIN INITIAL;
/* hand string to parser */
}
/* add to saved string for parser */
}


<COMMENT>.|\n { /* add to saved string for parser */ }


-John]

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