(flex.info)Diagnostics

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23 Diagnostics
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The following is a list of 'flex' diagnostic messages:

   * 'warning, rule cannot be matched' indicates that the given rule
     cannot be matched because it follows other rules that will always
     match the same text as it.  For example, in the following 'foo'
     cannot be matched because it comes after an identifier "catch-all"
     rule:

              [a-z]+    got_identifier();
              foo       got_foo();

     Using 'REJECT' in a scanner suppresses this warning.

   * 'warning, -s option given but default rule can be matched' means
     that it is possible (perhaps only in a particular start condition)
     that the default rule (match any single character) is the only one
     that will match a particular input.  Since '-s' was given,
     presumably this is not intended.

   * 'reject_used_but_not_detected undefined' or
     'yymore_used_but_not_detected undefined'.  These errors can occur
     at compile time.  They indicate that the scanner uses 'REJECT' or
     'yymore()' but that 'flex' failed to notice the fact, meaning that
     'flex' scanned the first two sections looking for occurrences of
     these actions and failed to find any, but somehow you snuck some in
     (via a #include file, for example).  Use '%option reject' or
     '%option yymore' to indicate to 'flex' that you really do use these
     features.

   * 'flex scanner jammed'.  a scanner compiled with '-s' has
     encountered an input string which wasn't matched by any of its
     rules.  This error can also occur due to internal problems.

   * 'token too large, exceeds YYLMAX'.  your scanner uses '%array' and
     one of its rules matched a string longer than the 'YYLMAX' constant
     (8K bytes by default).  You can increase the value by #define'ing
     'YYLMAX' in the definitions section of your 'flex' input.

   * 'scanner requires -8 flag to use the character 'x''.  Your scanner
     specification includes recognizing the 8-bit character ''x'' and
     you did not specify the -8 flag, and your scanner defaulted to
     7-bit because you used the '-Cf' or '-CF' table compression
     options.  See the discussion of the '-7' flag, Note: Scanner
     Options, for details.

   * 'flex scanner push-back overflow'.  you used 'unput()' to push back
     so much text that the scanner's buffer could not hold both the
     pushed-back text and the current token in 'yytext'.  Ideally the
     scanner should dynamically resize the buffer in this case, but at
     present it does not.

   * 'input buffer overflow, can't enlarge buffer because scanner uses
     REJECT'.  the scanner was working on matching an extremely large
     token and needed to expand the input buffer.  This doesn't work
     with scanners that use 'REJECT'.

   * 'fatal flex scanner internal error--end of buffer missed'.  This
     can occur in a scanner which is reentered after a long-jump has
     jumped out (or over) the scanner's activation frame.  Before
     reentering the scanner, use:
              yyrestart( yyin );
     or, as noted above, switch to using the C++ scanner class.

   * 'too many start conditions in <> construct!' you listed more start
     conditions in a <> construct than exist (so you must have listed at
     least one of them twice).