case-independent character range match bug, flex 2.5.25

[Bruce Lilly]

When given the -i option, flex not only treats upper- and
lower-case letters identically as individual characters,
it botches ranges if a specific alphabetic character is
used in specifying a range:

# cat test.l
/* input might be from a socket, and isatty may therefore be unreliable */
%option always-interactive


        /* RFC 2822: some control chars, all printing 7-bit chars except ']', 
'\\', and '[' */
dtext   ([\001-\010\013\014\016-\037!-Z^-\177])

%%

        /* domain literals */
{dtext} {
        return 2;
}

\]      {
        return 3;
}

.|\n    {
        return 1;
}
%%

int main(int argc, char **argv)
{
 int c;

 do switch((c = yylex())) {
   case 1:
   /*FALLTHROUGH*/
   case 2:
    if (yytext[0] == ']') {
     (void) fprintf(stderr, "Warning! Warning! Danger, Will Robinson! Flex is 
broken! (%d)\n", c);
     abort();
    }
  }
 while (c);
 return 0;
}

int yywrap(void)
{
 return 1;
}
# flex test.l
# cc -o test lex.yy.c
# echo 'abc[123]def' | ./test
# flex -i test.l
test.l:15: warning, rule cannot be matched
# cc -o test lex.yy.c
# echo 'abc[123]def' | ./test
Warning! Warning! Danger, Will Robinson! Flex is broken! (2)
ksh: 29994: Abort(coredump)