# Clarify the flex debug trace by substituting first line of each rule.

# Francois Pinard <pinard@iro.umontreal.ca>, July 1990.

#

# Rewritten to process correctly \n's in scanner input.

# BEGIN section modified to correct a collection of rules.

# Michal Jaegermann <michal@phys.ualberta.ca>, December 1993

#

# Sample usage:

#	flex -d PROGRAM.l

#	gcc -o PROGRAM PROGRAM.c -lfl

#	PROGRAM 2>&1 | gawk -f debflex.awk PROGRAM.l

#

# (VP's note: this script presently does not work with either "old" or

#  "new" awk; fixes so it does will be welcome)

BEGIN {

    # Insure proper usage.

    if (ARGC != 2) {

	print "usage: gawk -f debflex.awk FLEX_SOURCE 

	exit (1);

    }

    # Remove and save the name of flex source.

    source = ARGV[1];

    ARGC--;

    # Swallow the flex source file.

    line = 0;

    section = 1;

    while (getline 

	# Count the lines.

	line++;

	# Count the sections.  When encountering section 3,

	# break out of the awk BEGIN block.

	if (match ($0, /^%%/)) {

	    section++;

	    if (section == 3) {

		break;

	    }

	}

	else {

	    # Only the lines in section 2 which do not begin in a

	    # tab or space might be referred to by the flex debug

	    # trace.  Save only those lines.

	    if (section == 2 && match ($0, /^[^ \t]/)) {

		rules[line] = $0;

	    }

	}

    }

    dashes = "-----------------------------------------------------------";

    collect = "";

    line = 0;

}

# collect complete rule output from a scanner

$0 !~ /^--/ {

    collect = collect "\n" $0;

    next;

}

# otherwise we have a new rule - process what we got so far

{

    process();

}

# and the same thing if we hit EOF

END {

    process();

}

function process() {

    # splitting this way we loose some double dashes and

    # left parentheses from echoed input - a small price to pay

    n = split(collect, field, "\n--|[(]");

    # this loop kicks in only when we already collected something

    for (i = 1; i <= n; i++) {

	if (0 != line) {

	    # we do not care for traces of newlines.

	    if (0 == match(field[i], /\"\n+\"[)]/)) {

		if (rules[line]) {

		    text = field[i];

		    while ( ++i <= n) {

			text = text field[i];

		    }

		    printf("%s:%d: %-8s -- %s\n",

			   source, line, text, rules[line]);

		}

		else {

		    print;

		    printf "%s:%d: *** No such rule.\n", source, line;

		}

	    }

	    line = 0;

	    break;

	}

	if ("" != field[i]) {

	    if ("end of buffer or a NUL)" == field[i]) {

		print dashes;  # Simplify trace of buffer reloads

		continue;

	    }

	    if (match(field[i], /accepting rule at line /)) {

		# force interpretation of line as a number

		line = 0 + substr(field[i], RLENGTH);

		continue;

	    }

	    # echo everything else

	    printf("--%s\n", field[i]);

	}

    }

    collect = "\n" $0;  # ... and start next trace

}