to.do/Wilhelms.todo

PARSE.Y 344: ('rule'-rule " | re '$' ": There are some errors concerning
    trailing context. First of all the rule " re '$' " implies that this is
    no variable_trail_rule because the tail of it ( '$' ) has a fixed length
    of 1. The only possible reason for making this rule variable is when
    'previous_continued_action' is true. In this case 'variable_trail_rule'
    must be set and the beginning of the trailing part must be marked.
    However the variables 'varlength' and 'headcnt' have not the same meaning
    as in the rule " re2 re ". Here ( in the rule " re '$' " ) 'varlength'
    is true if the head ( 're' ) of the rule has variable length, and
    'headcnt' is still 0 because it isn't set during reduction of 're'.
    Therefore the test for a variable trailing rule
      " if ( ! varlength || headcnt != 0 ) "
    is wrong and should be removed.
    Also it is not necessary to set 'varlength' or 'headcnt' if you set
    " trailcnt = 1; ". If this rule is made variable then 'variable_trail_rule'
    is set and neither 'headcnt' nor 'trailcnt' are used in 'finish_rule()'.
    And if this rule is normal then the head may be variable or not, but in
    'finish_rule()' code is generated to reduce 'yy_cp' by 1.
    Finally I found no reason to create an epsilon-state and insert it in
    front of mkstate( '\n' ) instead of adding it behind. This epsilon-state
    should be marked as STATE_TRAILING_CONTEXT. Otherwise you get no warning
    of dangerous trailing context if you have a rule " x\n*$ " which was made
    variable with '|'.)

		|  re '$'
			{
			/* if ( trlcontxt )
			    {
			    synerr( "trailing context used twice" );
			    $$ = mkstate( SYM_EPSILON );
			    }

			else */ if ( previous_continued_action )
			    {
			    /* see the comment in the rule for "re2 re"
			     * above
			     */
			/*  if ( ! varlength || headcnt != 0 )  */
				{
				fprintf( stderr,
    "%s: warning - trailing context rule at line %d made variable because\n",
					 program_name, linenum );
				fprintf( stderr,
					 "      of preceding '|' action\n" );
				}

			/* mark as variable */
			/*  varlength = true;
			    headcnt = 0;  */

			    add_accept( $1, num_rules | YY_TRAILING_HEAD_MASK )
;
			    variable_trail_rule = true;
			    }

		/*	trlcontxt = true;

			if ( ! varlength )
			    headcnt = rulelen;

			++rulelen;  */
			trailcnt = 1;

			current_state_type = STATE_TRAILING_CONTEXT;
			eps = mkstate( SYM_EPSILON );
			current_state_type = STATE_NORMAL;

			$$ = link_machines( $1,
				 link_machines( mkstate( '\n' ), eps ) );
			}

DFA.C 618: (ntod(): The arrays 'targstate[]' and 'targfreq[]' can be
    maintained in a better way. Up to now it is possible that states are added
    to 'targstate[]' more than once, because the state 'newds' from the call
    to snstods() creates a new entry in 'targstate[]'. But 'newds' may already
    exist in 'targstate[]' !
    Another point is that 'targfreq[]' is not updated if "caseins && ! useecs"
    is true.
    My algorithm should solve these problems. However it could be simplified
    by replacing 'newds' by 'targ' and removing the statement "targ = newds;".
    Remark to the second point: I decremented the targfreq-counter if 'sym'
    was an uppercase letter and incremented it if 'sym' was a lowercase
    letter. The index 'i' of 'targfreq[i]' points to the correct position in
    'targstate[]' even if a new state was added.)

	for ( sym = 1; sym <= numecs; ++sym )
	    {
	    if ( symlist[sym] )
		{
		symlist[sym] = 0;

		if ( duplist[sym] == NIL )
		    { /* symbol has unique out-transitions */
		    numstates = symfollowset( dset, dsize, sym, nset );
		    nset = epsclosure( nset, &numstates, accset,
				       &nacc, &hashval );

		    if ( snstods( nset, numstates, accset,
				  nacc, hashval, &newds ) )
			{
			totnst = totnst + numstates;
			++todo_next;
			numas += nacc;

			if ( variable_trailing_context_rules && nacc > 0 )
			    check_trailing_context( nset, numstates,
				accset, nacc );
			}

		    targ = newds;
		    }

		else
		    {
		    /* sym's equivalence class has the same transitions
		     * as duplist(sym)'s equivalence class
		     */
		    targ = state[duplist[sym]];
		    }

		state[sym] = targ;

		if ( trace )
			fprintf( stderr, "\t%d\t%d\n", sym, targ );

		/* update frequency count for destination state */

		for ( i = 1; i <= targptr; ++i )
		    if ( targstate[i] == targ )
			    break;

		if ( i <= targptr )
		    {
		    ++targfreq[i];
		    ++numdup;
		    }
		else
		    {
		    targfreq[++targptr] = 1;
		    targstate[targptr] = targ;
		    ++numuniq;
		    }

		if ( caseins && ! useecs )
		    {
		    if ( sym >= 'A' && sym <= 'Z' )
			{
			--targfreq[i];
			--totaltrans;
			}
		    else if ( sym >= 'a' && sym <= 'z' )
			{
			++targfreq[i];
			++totaltrans;
			}
		    }

		++totaltrans;
		duplist[sym] = NIL;
		}
	    }


GEN.C 438: (gen_next_compressed_state(): I have rewritten the function
    'yy_try_NUL_trans()' so it really just tries to find out whether a
    transition on the NUL character goes to the jamstate or not. ( That means
    I removed each creation of backtracking information and the saving of the
    new state on the 'yy_state_buf[]'. )
    Therefore I removed the call for 'gen_backtracking()' here, because the
    function 'gen_next_compressed_state()' is also used in 'gen_NUL_trans()'.)

/*  gen_backtracking(); */

GEN.C 587ff: (gen_next_state(): Since the backtracking information is not
    created in 'gen_next_compressed_state()' any more, it is done here
    before the next state is computed ( for "compressed" tables ). This
    removes the bug that the backtracking information is created twice if
    'nultrans' is not NULL and 'gen_next_compressed_state()' is called.
    Finally I had to insert the creation of a "{" and a "}", because there
    is a local variable created in 'gen_next_compressed_state()'. ( These are
    needed only when backtracking information is really created.) )

    if ( ! fulltbl && ! fullspd )
	gen_backtracking();

    if ( worry_about_NULs && nultrans )
	{
	indent_puts( "if ( *yy_cp )" );
	indent_up();
	indent_puts( "{" );
	}
    else if ( ! fulltbl && ! fullspd && ! reject && num_backtracking > 0 )
	indent_puts( "{" );

    if ( fulltbl )
	indent_put2s( "yy_current_state = yy_nxt[yy_current_state][%s];",
		char_map );

    else if ( fullspd )
	indent_put2s( "yy_current_state += yy_current_state[%s].yy_nxt;",
		    char_map );

    else
	gen_next_compressed_state( char_map );

    if ( worry_about_NULs && nultrans )
	{
	indent_puts( "}" );
	indent_down();
	indent_puts( "else" );
	indent_up();

	indent_puts( "yy_current_state = yy_NUL_trans[yy_current_state];" );
	indent_down();
	}
    else if ( ! fulltbl && ! fullspd && ! reject && num_backtracking > 0 )
	indent_puts( "}" );

    if ( fullspd || fulltbl )
	gen_backtracking();

    if ( reject )
	indent_puts( "*yy_state_ptr++ = yy_current_state;" );
    }

GEN.C 553: (gen_next_match(): There is a problem if 'interactive' is true. In
    this case the scanner jams if the next state is the jamstate ( i.e.
    yy_base[yy_current_state] == jambase ). However the scanner reaches also
    the jamstate if the transition character is the NUL-character or if the
    end of the buffer is reached. Then in the EOB-action is decided whether
    this was really a NUL character or the end-of-buffer. ( If it was a NUL,
    scanning will be resumed. If it was the end-of-buffer, the buffer will be
    filled first, before scanning will be resumed. )
    These actions are not done if you use an 'interactive' scanner, because
    the EOB-action is not executed. Therefore you have to continue scanning,
    if you have just matched a NUL character ( i.e. *yy_cp == '\0' and
    yy_cp < &yy_current_buffer->yy_ch_buf[yy_n_chars] ) and if you are not
    already in the yamstate ( i.e. yy_current_state != jamstate ).
    Note that the '<' in " yy_cp < &yy_current_buffer->yy_ch_buf[yy_n_chars] "
    implies that the EOB action is *not* executed if the last match before the
    end-of-buffer was maximal.
    The following change in the algorithm results in a minor performance
    penalty because the additional conditions are tested only if you have
    reached the end of the match or if you are using NUL characters in your
    patterns.)

	if ( interactive )
	    {
	    printf( "while ( yy_base[yy_current_state] != %d\n", jambase );
	    set_indent( 4 );
	    indent_puts( "|| ( *yy_cp == '\\0'" );
	    indent_up();
	    indent_puts(
		" && yy_cp < &yy_current_buffer->yy_ch_buf[yy_n_chars]" );
	    do_indent();
	    printf( " && yy_current_state != %d ) );\n", jamstate );
	    set_indent( 2 );
	    }
	else
	    printf( "while ( yy_current_state != %d );\n", jamstate );

GEN.C 341: (gen_find_action(): Question: The variables 'yy_full_match',
    'yy_full_state' and 'yy_full_lp' are used only in the REJECT macro. Why
    do you not also test here on 'real_reject' before you create code to set
    these variables ( like you did in line 327ff for the action of the case
    " ( yy_act & YY_TRAILING_MASK ) " ) ?)

    New code beginning at line 338 to show the context:
	    indent_puts( "else" );
	    indent_up();
	    indent_puts( "{" );

	    if ( real_reject )
		{
		/* remember matched text in case we back up due to REJECT */
		indent_puts( "yy_full_match = yy_cp;" );
		indent_puts( "yy_full_state = yy_state_ptr;" );
		indent_puts( "yy_full_lp = yy_lp;" );
		}

	    indent_puts( "break;" );
	    indent_puts( "}" );
	    indent_down();

	    indent_puts( "++yy_lp;" );
	    indent_puts( "goto find_rule;" );
	    }


FLEX.SKEL 364,379: (YY_END_OF_BUFFER action: If it was really a NUL character
    which started this action, then 'yy_bp' points still at the beginning of
    the current run and 'yy_c_buf_p' points behind the NUL character.
    Contrast this with the situation after the call of 'yy_get_next_buffer()'!
    Therefore I removed the statement " yy_bp = yytext + YY_MORE_ADJ; "
    ( line 379 ) and replaced the statement
    " yy_c_buf_p = yytext + yy_amount_of_matched_text; " ( line 364 ) by the
    easier one " yy_c_buf_p = --yy_cp; ". Here 'yy_cp' is also adjusted.
    This guarantees that both 'yy_c_buf_p' and 'yy_cp' point at the NUL
    character. Therefore 'yy_cp' will have the correct value when it is needed
    after the call to 'yy_try_NUL_trans()' ( when we know whether we make a
    transition or not ).

    line 364:
		    yy_c_buf_p = --yy_cp;

    line 379:
		/*  yy_bp = yytext + YY_MORE_ADJ; */

GEN.C 632: (gen_NUL_trans(): I have rewritten 'yy_try_NUL_trans()'. The new
    version just finds out whether a transition on the NUL character goes to
    the jamstate or not. See also my remarks to 'gen_next_compressed_state()'.
    Note that the test " yy_is_jam = (yy_current_state == jamstate); " is
    also used, if 'interactive' is true. Otherwise 'yy_try_NUL_trans()' would
    return 0, if the NUL character was the last character of a pattern
    ( e.g. "x\0" ), and we therefore would not reach the last state.
    Remark: Change also the comment in FLEX.SKEL for this function.)

    FLEX.SKEL, line 583:
%% code to find the next state goes here

    GEN.C, line 632ff:
/*  int need_backtracking = (num_backtracking > 0 && ! reject);

    if ( need_backtracking )
	/ * we'll need yy_cp lying around for the gen_backtracking() * /
	indent_puts( "register YY_CHAR *yy_cp = yy_c_buf_p;" ); */

    GEN.C, line 674ff:
/*	if ( reject )
	    indent_puts( "*yy_state_ptr++ = yy_current_state;" ); */

	do_indent();

/*	if ( interactive )
	    printf( "yy_is_jam = (yy_base[yy_current_state] == %d);\n",
		    jambase );
	else */
	    printf( "yy_is_jam = (yy_current_state == %d);\n", jamstate );
	}

    /* if we've entered an accepting state, backtrack; note that
     * compressed tables have *already* done such backtracking, so
     * we needn't bother with it again
     */
/*  if ( need_backtracking && (fullspd || fulltbl) )
	{
	putchar( '\n' );
	indent_puts( "if ( ! yy_is_jam )" );
	indent_up();
	indent_puts( "{" );
	gen_backtracking();
	indent_puts( "}" );
	indent_down();
	} */
    }

GEN.C 1293: (make_tables(): The changed functionality of 'yy_try_NUL_trans()'
    implies changes in the EOB action. If the next state 'yy_next_state' is 0
    ( i.e. the jamstate ), you can immediately jump to 'yy_find_action'.
    Remember that 'yy_cp' was already adjusted to point at the NUL !
    Also you must not use the backtracking information because the actual
    state 'yy_current_state' may be an accepting state.
    If 'yy_next_state' is not the jamstate, we make a transition on the NUL.
    This requires the following actions:
    - Create backtracking information for compressed tables *before* we make
      the transition on NUL.
    - Now increment 'yy_cp' and set 'yy_current_state' to 'yy_next_state'.
      ( Note that 'yy_cp' points at the NUL up to now. )
    - Save the new state on the stack 'yy_state_buf[]' if 'reject' is true.
    - Create backtracking information *after* the transition, if 'fulltbl'
      or 'fullspd' is true.
    - Finally decide, if 'interactive' is true, whether scanning should be
      resumed at 'yy_match' or whether we have reached a final state and
      should jump to 'yy_find_action'. (Condition like in 'gen_next_match()'.)
      If 'interactive' is false, just resume scanning.)

    Corresponding code in FLEX.SKEL beginning at line 381:
		    if ( yy_next_state )
			{
			/* consume the NUL */
%% code to do backtracking for compressed tables and set up yy_cp goes here
			}
		    else
			goto yy_find_action;

    Code in GEN.C beginning at line 1293:
    /* first, deal with backtracking and setting up yy_cp if the scanner
     * finds that it should JAM on the NUL
     */
    skelout();
    set_indent( 6 );

    if ( ! fulltbl && ! fullspd )
	gen_backtracking();

    indent_puts( "++yy_cp;" );
    indent_puts( "yy_current_state = yy_next_state;" );

    if ( reject )
	indent_puts( "*yy_state_ptr++ = yy_current_state;" );

    if ( fulltbl || fullspd )
	gen_backtracking();

    if ( interactive )
	{
	do_indent();
	printf( "if ( yy_base[yy_current_state] != %d\n", jambase );
	indent_up();
	indent_puts( "|| ( *yy_cp == '\\0'" );
	indent_puts( "&& yy_cp < &yy_current_buffer->yy_ch_buf[yy_n_chars]" );
	do_indent();
	printf( "&& yy_current_state != %d ) )\n", jamstate );
	indent_puts( "goto yy_match;" );
	indent_down();
	indent_puts( "else" );
	indent_up();
	indent_puts( "goto yy_find_action;" );
	indent_down();
	}
    else
	indent_puts( "goto yy_match;" );

/*  if ( fullspd || fulltbl )
	indent_puts( "yy_cp = yy_c_buf_p;" );

    else
	{ / * compressed table * /
	if ( ! reject && ! interactive )
	    {
	    / * do the guaranteed-needed backtrack to figure out the match * /
	    indent_puts( "yy_cp = yy_last_accepting_cpos;" );
	    indent_puts( "yy_current_state = yy_last_accepting_state;" );
	    }
	} */

FLEX.SKEL 513: (yy_get_next_buffer(): Here is an error if 'yymore()' is active
    in the last match (i.e. yy_doing_yy_more == 1 and yy_more_len > 0). Then
    'number_to_move' will be (1 + yy_more_len), i.e. the previous character
    plus the additional characters for using 'yymore()'.)

	if ( number_to_move == 1 + YY_MORE_ADJ )
	    {
	    ret_val = EOB_ACT_END_OF_FILE;
	    yy_current_buffer->yy_eof_status = EOF_DONE;
	    }

	else
	    {
	    ret_val = EOB_ACT_LAST_MATCH;
	    yy_current_buffer->yy_eof_status = EOF_PENDING;
	    }
	}

GEN.C 1317: (make_tables(): In the generation of 'yy_get_previous_state()' the
    variable 'yy_bp' must be set to 'yytext + YY_MORE_ADJ' if 'bol_needed' is
    true. Otherwise 'yy_bp' points eventually at the beginning of the
    yymore-prefix instead of the current run.)

    if ( bol_needed )
	indent_puts( "register YY_CHAR *yy_bp = yytext + YY_MORE_ADJ;\n" );

FLEX.SKEL 589ff: (yyunput(): The function 'yyunput()' should be rewritten.
    First of all the example for 'unput()' in file flexdoc doesn't work:
	      {
	      int i;
	      unput( ')' );
	      for ( i = yyleng - 1; i >= 0; --i )
		  unput( yytext[i] );
	      unput( '(' );
	      }
    The actual version of 'yyunput()' modifies 'yyleng'. Therefore 'yyleng' is
    decremented by " unput( ')' ) " and the pattern to be pushed back has lost
    its last character. To avoid this just copy the 'yytext'-string and
    'yyleng' before you call 'unput()'.
    Another point is that 'yytext' and 'yyleng' could be maintained in a
    better way. ( Up to now 'yyleng' can become negative ! )
    I think it's better to say that the pushed back pattern should fulfill
    the beginning-of-line-condition if and only if the old pattern does
    ( excluding a possibly existing 'yymore'-prefix ! ).
    Up to now you have problems if there is a 'yymore'-prefix, because
    'yytext' will be corrupted by YY_DO_BEFORE_ACTION. ( This macro sets
    'yytext' to 'yy_bp - yy_more_len', but our 'yy_bp' points already at the
    beginning of the 'yymore'-prefix. )

    My version of 'yyunput()' reduces the 'yytext'-string by 1 for every
    pushed back character and decrements 'yyleng' until 'yytext' is the empty
    string. The beginning-of-line-condition is preserved when 'bol_needed' is
    true. ( Then the character before the current run is copied in front of
    the pushed back character. ) If there is a 'yymore'-prefix, 'yy_more_len'
    will be decremented if 'yy_cp' reaches the beginning of the current run.

    Remark: The parameter 'yytext' in " yyunput( c, yytext ) " is not really
    necessary since 'yytext' is a global variable. You could also set
    " register YY_CHAR *yy_bp = yytext; " at the beginning of 'yyunput()'.)

    Replace lines 622 - 623 in FLEX.SKEL:

    if ( yy_cp > yy_bp && yy_cp[-1] == '\n' )
	yy_cp[-2] = '\n';

    by

%% code to adjust yy_bp and yy_more_len goes here

    Add in GEN.C a function 'gen_yyunput()':
/* generate code to adjust yy_bp and yy_more_len in yyunput
 */

void gen_yyunput()

    {
    if ( yymore_used )
	indent_puts( "yy_bp += YY_MORE_ADJ;\n" );

    if ( bol_needed )
	indent_puts( "yy_cp[-2] = yy_bp[-1];\n" );

    if ( yymore_used )
	{
	indent_puts( "if ( (yy_cp == yy_bp) && YY_MORE_ADJ )" );
	indent_up();
	indent_puts( "--yy_more_len;" );
	indent_down();
	indent_puts( "else" );
	indent_up();
	indent_puts( "--yy_bp;" );
	indent_down();
	}
    else
	indent_puts( "--yy_bp;" );
    }

    Finally add in the function 'make_tables()' behind the call of
    'gen_NUL_trans()' in line 1328:

    skelout();
    gen_yyunput();

FLEX.SKEL 642,658: (input(): There is an error in 'input()' if the end of
    'yy_current_buffer' is reached and 'yymore' is active. Then
    'yy_get_next_buffer()' is called which function assumes that 'yytext'
    points at the beginning of the 'yymore'-prefix. This function can't
    recognize the end of the input stream correctly and therefore returns
    EOB_ACT_LAST_MATCH instead of EOB_ACT_END_OF_FILE. Also if the end of
    the input file isn't reached yet (EOB_ACT_CONTINUE_SCAN) at least one
    character will be lost.
    To avoid this error just turn off 'yy_doing_yy_more'. Then you need
    not to adjust with YY_MORE_ADJ in lines 667 and 682. However you have to
    use a function 'gen_input()', because 'yy_doing_yy_more' does not exist
    if 'yymore_used' is false.

    ( Another solution is to adjust 'yytext':
    " yytext = yy_c_buf_p - YY_MORE_ADJ; ", line 658. )

    I think the trick with "yy_did_buffer_switch_on_eof" should be done here
    the same way as in the YY_END_OF_BUFFER action.
    Finally I removed the variable 'yy_cp' and used 'yy_c_buf_p' instead.)

#ifdef __cplusplus
static int yyinput()
#else
static int input()
#endif

    {
    int c;

    *yy_c_buf_p = yy_hold_char; /* yy_cp not needed */

    if ( *yy_c_buf_p == YY_END_OF_BUFFER_CHAR )
	{
	/* yy_c_buf_p now points to the character we want to return.
	 * If this occurs *before* the EOB characters, then it's a
	 * valid NUL; if not, then we've hit the end of the buffer.
	 */
	if ( yy_c_buf_p < &yy_current_buffer->yy_ch_buf[yy_n_chars] )
	    /* this was really a NUL */
	    *yy_c_buf_p = '\0';

	else
	    { /* need more input */
%% code to turn off yy_doing_yy_more and yy_more_len goes here
	    yytext = yy_c_buf_p;
	    ++yy_c_buf_p;

	    switch ( yy_get_next_buffer() )
		{
		case EOB_ACT_END_OF_FILE:
		    {
		    yy_did_buffer_switch_on_eof = 0;

		    if ( yywrap() )
			{
			yy_c_buf_p = yytext; /* + YY_MORE_ADJ not needed */
			return ( EOF );
			}
		    else
			{
			if ( ! yy_did_buffer_switch_on_eof )
			    YY_NEW_FILE;
			}

#ifdef __cplusplus
		    return ( yyinput() );
#else
		    return ( input() );
#endif
		    }
		    break;

		case EOB_ACT_CONTINUE_SCAN:
		    yy_c_buf_p = yytext; /* + YY_MORE_ADJ not needed */
		    break;

		case EOB_ACT_LAST_MATCH:
#ifdef __cplusplus
		    YY_FATAL_ERROR( "unexpected last match in yyinput()" );
#else
		    YY_FATAL_ERROR( "unexpected last match in input()" );
#endif
		}
	    }
	}

    c = *yy_c_buf_p;
    yy_hold_char = *++yy_c_buf_p;

    return ( c );
    }

    Add in GEN.C a function 'gen_input()':
/* generate code to turn off yy_doing_yy_more and yy_more_len in input
 */

void gen_input()

    {
    if ( yymore_used )
	indent_puts( "yy_doing_yy_more = yy_more_len = 0;" );
    }

    Finally add in the function 'make_tables()' behind the call of
    'gen_yyunput()':

    set_indent( 3 );
    skelout();
    gen_input();

PARSE.Y 54: ( 'goal'-rule: If there is no rule in the input file, the end of
    the prolog is not marked yet, because 'flexscan()' is still in the start
    condition <SECT2PROLOG> and the rule <SECT2PROLOG><<EOF>> is not done up
    to now. Therefore mark the end of prolog here, before you add the default
    rule. I test here on " num_rules == 1 ", because the 'initforrule'-rule
    increments 'num_rules' before this action is executed.)

			if ( num_rules == 1 )
			    fprintf( temp_action_file, "%%%% end of prolog\n" )
;

SCAN.L 255: ( '<SECT2PROLOG><<EOF>>'-rule: If there are no rules at all in
    the input file, then this rule will be executed at the end of
    'make_tables()'. At this point 'temp_action_file' was closed for writing
    and has been reopened for reading. The macro MARK_END_OF_PROLOG will
    therefore lead to a write-error.
    To avoid this error add the condition " if ( num_rules == 0 ) ". If this
    rule is executed at the end of 'make_tables()' there will be at least the
    default rule, i.e. 'num_rules' will be greater than 0.
    Remark: This correction together with the one before will allow an input
    file which just consists of "%%". ( Copy 'stdin' to 'stdout'. ))

<SECT2PROLOG><<EOF>>		{
			if ( num_rules == 0 )
			    MARK_END_OF_PROLOG;
			yyterminate();
			}

MISC.C 376: ( flexfatal(): The call of 'flexend( 1 )' will lead to an
    infinite loop if 'flexfatal()' is called from 'flexend()'. I therefore
    introduced the flag 'doing_flexend' to prevent 'flexend()' to be called
    more than once.)

    Replace the function call 'flexend( 1 );' in GEN.C, line 376, by
    if ( ! doing_flexend )
	flexend( 1 );

    Set 'doing_flexend' at the beginning of 'flexend()' in MAIN.C, line 195:
    doing_flexend = true;

    Add in FLEXDEF.H, line 381, the declaration of 'doing_flexend':
extern int yymore_used, reject, real_reject, continued_action, doing_flexend;

    Add in FLEXDEF.H, line 376, a comment for this variable:
 * doing_flexend - true if flexend() has been started

    Initialize 'doing_flexend' in 'flexinit()' in MAIN.C, line 401:
    yymore_used = continued_action = reject = doing_flexend = false;

FLEX.SKEL 94: ( 'YY_INPUT()'-macro: I have problems with 'fileno()' and
    'read()'.
    I used the C Compiler of the BORLAND C++ Compiler and compiled the created
    scanner with the option 'ANSI keywords'.
    In this compiler the prototype of the function 'read(...)' is declared in
    the header file 'io.h' and not in 'stdio.h'. Therefore I get a warning.
    Real trouble caused 'fileno' which is defined as macro in 'stdio.h':
	#define fileno(f)       ((f)->fd)
    However this macro does not belong to the 'ANSI keywords' because it is
    define'd under the condition " #if !__STDC__ ". Therefore I get a warning
    and a linker error that the function 'fileno()' does not exist.
    (I can avoid this problem by adding the above define-macro in the *.l file
    or by replacing the option 'ANSI keywords' by 'Borland C++ keywords'.))