source: trunk/essentials/sys-devel/flex/examples/debflex.awk

# 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 <DEBUG_OUTPUT";
        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 <source) {

        # 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
}