Simple script to count NLOC?

Question

Do you know a simple script to count NLOCs (netto lines of code). The script should count lines of C Code. It should not count empty lines or lines with just braces. But it doesn't need to be overly exact either.

Answer 1

If the comments can still be in, the standard unix tool are sufficent:

grep  -x -v "[[:space:]}{]*" files.c  | wc

Answer 2

Ohloh offers the free Ohcount which counts lines of code and comments.

Answer 3

Locmetrics works well.

Answer 4

Here's a simple Perl script eLOC.pl:

#!/usr/bin/perl -w
# eLOC - Effective Lines of Code Counter
# JFS (2005)
#
# $ perl eLOC.pl --help
#
use strict;
use warnings;
use sigtrap;
use diagnostics;

use warnings::register;
no warnings __PACKAGE__;
sub DEBUG { 0 }

use English qw( -no_match_vars ) ;  # Avoids regex performance penalty
use Getopt::Long qw(:config gnu_getopt);
use File::DosGlob 'glob';
use Pod::Usage;


our $VERSION = '0.01';

# globals
use constant NOTFILENAME => undef;
my %counter = ( 
    'PHYS'          => 0, 
    'ELOC'          => 0, 
    'PURE_COMMENT'  => 0,
    'BLANK'         => 0,
    'LLOC'          => 0,
    'INLINE_COMMENT'=> 0,
    'LOC'           => 0,
);
my %header = (
    "eloc"      =>  "eloc",
    "lloc"      =>  "lloc",
    "loc"       =>  "loc",
    "comment"   =>  "comment",
    "blank"     =>  "blank",
    "newline"   =>  "newline",
    "logicline" =>  "lgcline",
);
my %total = %counter; # copy
my $c = \%counter; # see format below
my $h = \%header;  # see top format below
my $inside_multiline_comment = 0;
my $filename = NOTFILENAME;
my $filecount = 0;
my $filename_header = "file name";

# process input args
my $version = '';
my $help = '';
my $man = '';
my $is_deterministic = '';
my $has_header = '';

print STDERR "Input args:'" if DEBUG;
print STDERR (join("|",@ARGV),"'\n") if DEBUG;

my %option = ('version' => \$version,
    'help' => \$help,   
    'man'  => \$man,
    'deterministic' => \$is_deterministic,
    'header' => \$has_header
);
GetOptions( \%option, 'version',    'help', 'man',
    'eloc|e', # print the eLOC counts
    'lloc|s', # print the lLOC counts (code statements)
    'loc|l' , # print the LOC counts (eLOC + lines of a single brace or parenthesis)
    'comment|c'    , # print the comments counts (count lines which contains a comment)
    'blank|b'      , # print the blank counts
    'newline|n'    , # print the newline count
    'logicline|g'  , # print the logical line count (= LOC + Comment Lines + Blank Lines)   
    'deterministic', # print the LOC determination for every line in the source file
    'header',        # print header line
) or invalid_options("$0: invalid options\nTry `$0 --help' for more information.");

version()                                   if $version;
pod2usage(-exitstatus => 0, -verbose => 1)  if $help ;
pod2usage(-exitstatus => 0, -verbose => 2)  if $man;

#
$has_header = 1 if $is_deterministic && $has_header eq '';

#format for print_loc_metric()
my ($format, $format_top) = make_format(); 
print STDERR "format:\n" if DEBUG > 10;
print STDERR $format if DEBUG > 10;
eval $format;
die $@ if $@; # $EVAL_ERROR

if(DEBUG>10) {
    print STDERR ("format_top:\n", $format_top);
}
if( $has_header) {
    eval $format_top;
    die $@ if $@; # $EVAL_ERROR 
}

# process files
print STDERR ("Input args after Getopts():\n",
    join("|",@ARGV),"\n") if DEBUG > 10;

expand_wildcards();
@ARGV = '-' unless @ARGV;
foreach my $fn (@ARGV) {
    $filename = $fn;
    unless (open(IN, "<$filename")) {
        warn "$0: Unable to read from '$filename': $!\n";
        next;
    }
    print STDERR "Scanning $filename...\n" if DEBUG;

    clear_counters();
    generate_loc_metric();  

    $filecount++;

    print_loc_metric();                     

    close(IN)
        or warn "$0: Could not close $filename: $!\n";      
}

# print total
if($filecount > 1) {
    $filename = "total";
    $c = \%total;
    print_loc_metric();
}
exit 0;

#-------------------------------------------------
sub wsglob {
    my @list = glob;
    @list ? @list : @_; #HACK: defence from emtpy list from glob()
}
sub expand_wildcards {
    print STDERR ("Input args before expand_wildcards():\n",
        join("|",@ARGV),"\n") if DEBUG;

    {       
        @ARGV = map( /['*?']/o ? wsglob($_) : $_ , @ARGV);
    }   
    print STDERR ("Input args after expand_wildcards():\n",
        join("|",@ARGV),"\n") if DEBUG; 
}
sub clear_counters {
    for my $name ( keys %counter) {
        $counter{$name} = 0;
    }   
}
sub make_format {
    my $f = 'format STDOUT =' . "\n";
    $f .= '# LOC, eLOC, lLOC, comment, blank, newline, logicline and filename' . "\n";
    my $f_top = 'format STDOUT_TOP =' . "\n";   
    my $console_screen_width = (get_terminal_size())[0];
    print STDERR '$console_screen_width=' . $console_screen_width ."\n" if DEBUG>10;
    $console_screen_width = 100 if $console_screen_width < 0;
    my $is_print_specifiers_set = 
         ($option{"eloc"} or
         $option{"lloc"} or
         $option{"loc"} or
         $option{"comment"} or
         $option{"blank"} or
         $option{"newline"} or
         $option{"logicline"});

    my %o = %option;
    my $fc = 0;
    if( $is_print_specifiers_set ) {

        $fc++ if $o{"eloc"};
        $fc++ if $o{"lloc"};
        $fc++ if $o{"loc"};
        $fc++ if $o{"comment"};
        $fc++ if $o{"blank"};
        $fc++ if $o{"newline"};
        $fc++ if $o{"logicline"};
        if( $fc == 0 ) { die "$0: assertion failed: field count is zero" }
    }
    else {
        # default
        $fc = 7;
        $o{"loc"}       = 1;       
        $o{"eloc"}      = 1;         
        $o{"lloc"}      = 1;      
        $o{"comment"}   = 1;   
        $o{"blank"}     = 1;     
        $o{"newline"}   = 1;   
        $o{"logicline"} = 1;        
    }
    if (DEBUG > 10) {
        while( (my ($name, $value) = each %{o}) ) {
            print STDERR "name=$name, value=$value\n";
        }       
    }


    # picture line  
    my $field_format = '@>>>>>> ';
    my $field_width = length $field_format;
    my $picture_line = $field_format x $fc;     
    #   place for filename
    $picture_line .= '^';       
    $picture_line .= '<' x ($console_screen_width - $field_width * $fc - 2);
    $picture_line .= "\n";  
    $f .= $picture_line;
    $f_top .= $picture_line;
    # argument line
    $f .=   '$$c{"LOC"}, '      ,$f_top .= '$$h{"loc"}, '       if $o{"loc"};
    $f .=   '$$c{"ELOC"}, '     ,$f_top .= '$$h{"eloc"}, '      if $o{"eloc"};      
    $f .=   '$$c{"LLOC"}, '     ,$f_top .= '$$h{"lloc"}, '      if $o{"lloc"};
    $f .=   '$$c{"comment"}, '  ,$f_top .= '$$h{"comment"}, '   if $o{"comment"};
    $f .=   '$$c{"BLANK"}, '    ,$f_top .= '$$h{"blank"}, '     if $o{"blank"};
    $f .=   '$$c{"PHYS"}, '     ,$f_top .= '$$h{"newline"}, '   if $o{"newline"};
    $f .=   '$$c{"logicline"}, ',$f_top .= '$$h{"logicline"}, ' if $o{"logicline"};
    $f .=  '$filename' . "\n";
    $f_top .= '$filename_header' . "\n";        

    # 2nd argument line for long file names
    $f .=   '^';    
    $f .= '<' x ($console_screen_width-2);
    $f .= '~~'  . "\n"
            .' $filename'  . "\n";
    $f .='.' . "\n";
    $f_top .='.' . "\n";
    return ($f, $f_top);
}
sub generate_loc_metric {
    my $is_concatinated = 0;
    LINE: while(<IN>)
    {
        chomp;      
        print if $is_deterministic && !$is_concatinated;        

        # handle multiline code statements
        if ($is_concatinated = s/\\$//) {
            warnings::warnif("$0: '\\'-ending line concantinated");
            increment('PHYS');
            print "\n" if $is_deterministic;
            my $line = <IN>;
            $_ .= $line;
            chomp($line);
            print $line if $is_deterministic;
            redo unless eof(IN);            
        }               

        # blank lines, including inside comments, don't move to next line here
        increment('BLANK')                  if( /^\s*$/ );  

        # check whether multiline comments finished
        if( $inside_multiline_comment && m~\*/\s*(\S*)\s*$~ ) {
            $inside_multiline_comment = 0;
            # check the rest of the line if it contains non-whitespace characters
            #debug $_ = $REDO_LINE . $1, redo LINE if($1);
            warnings::warnif("$0: expression '$1' after '*/' discarded") if($1);
            # else mark as pure comment
            increment('PURE_COMMENT');
            next LINE;
        }
        # inside multiline comments
        increment('PURE_COMMENT'), next LINE if( $inside_multiline_comment );

        # C++ style comment at the begining of line (except whitespaces)
        increment('PURE_COMMENT'), next LINE if( m~^\s*//~ ); 

        # C style comment at the begining of line (except whitespaces)
        if ( m~^\s*/\*~ ) {
            $inside_multiline_comment = 1 unless( m~\*/~ );
            increment('PURE_COMMENT'),  next LINE;
        }
        # inline comment, don't move to next line here
        increment('INLINE_COMMENT')        if ( is_inline_comment($_) );

        # lLOC implicitly incremented inside is_inline_comment($)

        #
        increment('LOC')                    unless( /^\s*$/ );

        # standalone braces or parenthesis  
                                  next LINE if( /^\s*(?:\{|\}|\(|\))+\s*$/ );           

        # eLOC is not comments, blanks or standalone braces or parenthesis
        #   therefore just increment eLOC counter here
        increment('ELOC'),        next LINE unless( /^\s*$/ );
    }
    continue {
        increment('PHYS');
        print " [$.]\n" if $is_deterministic; # $INPUT_LINE_NUMBER
    }
}

sub print_loc_metric {
    $$c{'comment'} = $$c{'PURE_COMMENT'} + $$c{'INLINE_COMMENT'}; 
    # LOC + Comment Lines + Blank Lines 
    $$c{'logicline'} = $$c{'LOC'} + $$c{'comment'} + $$c{'BLANK'};
    unless (defined $filename) { 
        die "print_loc_metric(): filename is not defined";
    }       

    my $fn = $filename;
    $filename = "", $filename_header = "" 
        unless($#ARGV);
    print STDERR ("ARGV in print_loc_metric:" , join('|',@ARGV), "\n") 
        if DEBUG;
    write STDOUT; # replace with printf
    $filename = $fn;
}
sub increment {
    my $loc_type = shift;
    defined $loc_type
        or die 'increment(\$): input argument is undefined';    

    $counter{$loc_type}++;
    $total{$loc_type}++;
    print "\t#". $loc_type ."#" if $is_deterministic;   
}

sub is_inline_comment {
    my $line = shift;
    defined $line 
        or die 'is_inline_comment($): $line is not defined';

    print "\n$line" if DEBUG > 10;  

# here: line is not empty, not begining both C and C++ comments signs,
#       not standalone '{}()', not inside multiline comment,
#       ending '\' removed (joined line created if needed)

# Possible cases: 
#   - no C\C++ comment signs                        => is_inline_comment = 0
#   - C++ comment (no C comment sign)
#       * no quote characters                       => is_inline_comment = 1
#       * at least one comment sign is not quoted   => is_inline_comment = 1
#       * all comment signs are quoted              => is_inline_comment = 0
#   - C comment (no C++ comment sign)
#       * no quote characters                       => is_inline_comment = 1,
#           ~ odd number of '/*' and '*/'           => $inside_multiple_comment = 1                             
#           ~ even number                           => $inside_multiple_comment = 0
#       * etc...
#   - ...
# algorithm: move along the line from left to right
# rule: quoted comments are not counted
# rule: quoted by distinct style quotes are not counted
# rule: commented quotes are not counted
# rule: commented distinct style comments are not counted
# rule: increment('LLOC') if not-quoted, not-commented
#           semi-colon presents in the line except that two 
#           semi-colon in for() counted as one.

# 
$_ = $line; #hack: $_ = $line inside sub
#   state
my %s = (
    'c'     => 0, # c slash star - inside c style comments
    'cpp'   => 0, # c++ slash slash - inside C++ style comment
    'qm'    => 0, # quoted mark - inside quoted string
    'qqm'   => 0, # double quoted - inside double quoted string
);
my $has_comment = 0;
# find state
LOOP:
    {
      /\G\"/gc  &&  do { # match double quote
                            unless( $s{'qm'} || $s{'c'} || $s{'cpp'} ) {
                                    # toggle 
                                $s{'qqm'} = $s{'qqm'} ? 0 : 1; 
                            }
                            redo LOOP;
                    };
      /\G\'/gc  &&  do { # match single quote
                            unless( $s{'qqm'} || $s{'c'} || $s{'cpp'} ) {
                                    # toggle 
                                $s{'qm'} = $s{'qm'} ? 0 : 1; 
                            }
                            redo LOOP;
                    };
      m~\G//~gc &&  do { # match C++ comment sign
                            unless( $s{'qm'} || $s{'qqm'} || $s{'c'} ) {
                                    # on
                                $has_comment = 1;
                                $s{'cpp'} = 1; 
                            } 
                            redo LOOP;
                    };
      m~\G/\*~gc    &&  do { # match begining C comment sign
                            unless( $s{'qm'} || $s{'qqm'} || $s{'cpp'} ) {
                                    # on
                                $has_comment = 1;
                                $s{'c'} = $s{'c'} ? 1 : 1; 
                            } 
                            redo LOOP;
                    };
      m~\G\*/~gc    &&  do { # match ending C comment sign
                            unless( $s{'qm'} || $s{'qqm'} || $s{'cpp'} ) {
                                    # off                                   
                                if( $s{'c'} ) {                                     
                                    $s{'c'} = 0;
                                }
                                else {
                                    die 'is_inline_comment($): unexpected c style ending comment sign'.
                                        "\n'$line'";
                                }
                            } 
                            redo LOOP;
                    };
      /\Gfor\s*\(.*\;.*\;.*\)/gc    &&  do { # match for loop
                            unless( $s{'qm'} || $s{'qqm'} || $s{'cpp'} || $s{'c'} ) {
                                # not-commented, not-quoted semi-colon                                  
                                increment('LLOC');
                            }
                            redo LOOP;
                    };                                          
      /\G\;/gc  &&  do { # match semi-colon
                            unless( $s{'qm'} || $s{'qqm'} || $s{'cpp'} || $s{'c'} ) {
                                # not-commented, not-quoted semi-colon
                                # not inside for() loop
                                increment('LLOC');
                            }
                            redo LOOP;
                    };                      
      /\G./gc   &&  do { # match any other character
                            # skip 1 character
                            redo LOOP;
                    };
      /\G$/gc   &&  do { # match end of the line
                            last LOOP;
                    };                      
      #default
        die 'is_inline_comment($): unexpected character in the line:' .
            "\n'$line'";
    }
# apply state
    $inside_multiline_comment = $s{'c'};
    return $has_comment;
}

sub version {
#   TODO: version implementation
    print <<"VERSION";
NAME v$VERSION
Written by AUTHOR

COPYRIGHT AND LICENSE
VERSION

exit 0;
}

sub invalid_options {
    print STDERR (@_ ,"\n");
    exit 2;
}

sub get_terminal_size {
    my ($wchar, $hchar) = ( -1, -1); 
    my $win32console = <<'WIN32_CONSOLE';   
        use Win32::Console; 
        my $CONSOLE = new Win32::Console(); 
        ($wchar, $hchar) = $CONSOLE->MaxWindow();
WIN32_CONSOLE

    eval($win32console); 
    return ($wchar, $hchar) unless( $@ );
    warnings::warnif($@); # $EVAL_ERROR

    my $term_readkey = <<'TERM_READKEY';
        use Term::ReadKey; 
        ($wchar,$hchar, $wpixels, $hpixels) = GetTerminalSize(); 
TERM_READKEY

    eval($term_readkey); 
    return ($wchar, $hchar) unless( $@ );

    warnings::warnif($@); # $EVAL_ERROR 
    my $ioctl = <<'IOCTL'; 
        require 'sys/ioctl.ph'; 
        die "no TIOCGWINSZ " unless defined &TIOCGWINSZ; 
        open(TTY, "+</dev/tty")                     
            or die "No tty: $!"; 
        unless (ioctl(TTY, &TIOCGWINSZ, $winsize='')) { 
            die sprintf "$0: ioctl TIOCGWINSZ (%08x: $!)\n", 
                    &TIOCGWINSZ; 
        } 
        ($hchar, $wchar, $xpixel, $ypixel) = 
            unpack('S4', $winsize); # probably $hchar & $wchar should be swapped here 
IOCTL

    eval($ioctl); 
    warnings::warnif($@) if $@ ; # $EVAL_ERROR  

    return ($wchar, $hchar); 
}

1;
__END__ 

=head1 NAME

eLOC - Effective Lines of Code Counter

=head1 SYNOPSIS

B<eloc> B<[>OPTIONB<]...> B<[>FILEB<]...>

Print LOC, eLOC, lLOC, comment, blank, newline and logicline counts 
for each FILE, and a total line if more than one FILE is specified.
See L</"LOC Specification"> for more info, use `eloc --man'.

  -e, --eloc             print the {E}LOC counts
  -s, --lloc             print the lLOC counts (code {S}tatements)
  -l, --loc              print the {L}OC counts (eLOC + lines of a single brace or parenthesis)
  -c, --comment          print the {C}omments counts (count lines which contains a comment)
  -b, --blank            print the {B}lank counts
  -n, --newline          print the {N}ewline count
  -g, --logicline        print the lo{G}ical line count (= LOC + Comment Lines + Blank Lines)
      --deterministic    print the LOC determination for every line in the source file
      --header           print header line
      --help display this help and exit
      --man  display full help and exit
      --version  output version information and exit

With no FILE, or when FILE is -, read standard input.      

Metrics counted by the program are based on narration from 
http://msquaredtechnologies.com/m2rsm/docs/rsm_metrics_narration.htm

=for TODO: Comment Percent = Comment Line Count / Logical Line Count ) x 100      

=for TODO: White Space Percentage = (Number of spaces / Number of spaces and characters) * 100       

=head1 DESCRIPTION

eLOC is a simple LOC counter. See L</"LOC Specification">. 

=head2 LOC Specification

=over 1

=item LOC

Lines Of Code = eLOC + lines of a single brace or parenthesis

=item eLOC

An effective line of code or eLOC is the measurement of all lines that are 
not comments, blanks or standalone braces or parenthesis. 
This metric more closely represents the quantity of work performed. 
RSM introduces eLOC as a metrics standard.
See http://msquaredtechnologies.com/m2rsm/docs/rsm_metrics_narration.htm

=item lLOC

Logical lines of code represent a metrics for those line of code which form 
code statements.  These statements are terminated with a semi-colon.  

The control line for the "for" loop contain two semi-colons but accounts 
for only one semi colon.
See http://msquaredtechnologies.com/m2rsm/docs/rsm_metrics_narration.htm

=item comment

comment = pure comment + inline comment



=over

=item pure comment

Comment lines represent a metrics for pure comment line without any code in it.
See L</"inline comment">.

=item inline comment

Inline comment line is a line which contains both LOC line and pure comment.

Inline comment line and pure comment line (see L</"pure comment">)
are mutually exclusive, that is a given physical line cannot be an inline comment
line and a pure comment line simultaneously.

=over

=item Example:

    static const int defaultWidth = 400;        // value provided in declaration

=back

=back

=item blank

Blank line is a line which contains at most whitespaces.
Blank lines are counted inside comments too.

=item logicline

The logical line count = LOC + Comment Lines + Blank Lines

=back

=head1 KNOWN BUGS AND LIMITATIONS

=over

=item

It supports only C/C++ source files.

=item

Comments inside for(;;) statements are not counted

=over

=item Example:

    for(int i = 0; i < N /*comment*/; i++ );        #LLOC#  #LLOC#  #LOC#   #ELOC#  #PHYS# [1]

=back

=item

'\'-ending lines are concatinated ( though newline count is valid)

=item

Input from stdin is not supported in the case 
the script is envoked solely by name without explicit perl executable.

=item

Wildcards in path with spaces are not supported (like GNU utilities).

=back

=over

=begin fixed
=item Limitation: single source file

    Only one source file at time supported

=item Limitation: LLOC is unsupported

    The logical lines of code metric is unsupported. 

=item missed inline comment for C style comment

    #include <math.h> /* comment */ #ELOC#  #PHYS# [2]

But must be
    #include <math.h> /* comment */ #INLINE_COMMENT#    #ELOC#  #PHYS# [2]

=item wrong LOC type for the code after '*/'

    /* another  #PURE_COMMENT#  #PHYS# [36]
    trick   #PURE_COMMENT#  #PHYS# [37]
    */  i++;    #PURE_COMMENT#  #PHYS# [38]

In the last line must be 

    #INLINE_COMMENT# #PHYS# [38]

=end fixed

=back

=head1 SEE ALSO

Metrics counted by the program are based on narration from L<http://msquaredtechnologies.com/m2rsm/docs/rsm_metrics_narration.htm>

=cut

Answer 5

Looking NLOC on the Net, I found mostly "Non-commented lines of code".
You don't specify if comments must be skipped...
So if I stick to your current message, the following one-liner in Perl should do the job:

perl -pe "s/^\s*[{}]?\s*\n//" Dialog.java | wc -l

I can extend it to handle line comments:

perl -pe "s#^\s*[{}]?\s*\n|^\s*//.*\n##" Dialog.java | wc -l

or perhaps

perl -pe "s#^\s*(?:[{}]?\s*|//.*)\n##" Dialog.java | wc -l

Handling block comments is slightly more tricky (I am not a Perl expert!).

[EDIT] Got it... First part can be probably improved (shorter). Was fun to experiment with.

perl -e "$x = join('', <>); $x =~ s#/\*.*?\*/##gs; print $x" Dialog.java | perl -pe "s#^\s*(?:[{}]?\s*|//.*)\n##" | wc -l

PS.: I use double quotes because I tested on Windows...

Answer 6

I have a program called scc that strips C comments (and C++ comments, though with C99 they're the same). Apply that plus a filter to remove blank lines and, if so desired, lines containing just open and close braces, to generate the line counts. I've used that on internal projects - not needed to discount open/close braces. Those scripts were more complex, comparing the source code for two different versions of a substantial project stored in ClearCase. They also did statistics on files added and removed, and on lines added and removed from common files, etc.

Not counting braces makes quite a difference:

Black JL: co -q -p scc.c | scc | sed '/^[       ]*$/d' | wc -l
     208
Black JL: co -q -p scc.c | scc | sed '/^[       {}]*$/d' | wc -l
     144
Black JL: co -p -q scc.c | wc -l
     271
Black JL:

So, 144 lines under your rules; 208 counting open and close brace lines; 271 counting everything.

Lemme know if you want the code for scc (send email to first dot last at gmail dot com). It's 13 KB of gzipped tar file including man page, torture test, and some library files.

---

@litb commented that 'cpp -fpreprocessed -P file' handles stripping of comments. It mostly does. However, when I run it on the stress test for SCC, it complains when (in my opinion) it should not:

SCC has been trained to handle 'q' single quotes in most of
the aberrant forms that can be used. '\0', '\', '\'', '\\
n' (a valid variant on '\n'), because the backslash followed
by newline is elided by the token scanning code in CPP before
any other processing occurs.

When the CPP from GCC 4.3.2 processes this, it complains (warns):

SCC has been trained to handle 'q' single quotes in most of
<stdin>:2:56: warning: missing terminating ' character
the aberrant forms that can be used. '\0', '\', '\'', '\\
<stdin>:3:27: warning: missing terminating ' character
n' (a valid variant on '\n'), because the backslash followed
by newline is elided by the token scanning code in CPP before
any other processing occurs.

Section 5.1.1.2 Translation Phases of the C99 standard says:

The precedence among the syntax rules of translation is specified by the following phases.(Footnote 5)

1. Physical source file multibyte characters are mapped, in an implementation-defined manner, to the source character set (introducing new-line characters for end-of-line indicators) if necessary. Trigraph sequences are replaced by corresponding single-character internal representations.

2. Each instance of a backslash character () immediately followed by a new-line character is deleted, splicing physical source lines to form logical source lines. Only the last backslash on any physical source line shall be eligible for being part of such a splice. A source file that is not empty shall end in a new-line character, which shall not be immediately preceded by a backslash character before any such splicing takes place.

Footnote 5 is:

(5) Implementations shall behave as if these separate phases occur, even though many are typically folded together in practice.

Consequently, in my view, CPP is mishandling phase two in the example text. Or, at least, the warning is not what I want - the construct is valid C and it is not self-evident that the warning is warranted.

Granted, it is an edge case, and extra warnings are permitted. But it would annoy the living daylights out of me. If I didn't have my own, possibly better tool for the job, then using 'cpp -fpreprocessed -P' would do - it is an extreme edge case that I'm complaining about (and, it might be legitimate to argue that it is more likely that there is a problem than not -- though a better heuristic would observe that the line was spliced and the result was a legitimate single character constant and therefore the complaint should be suppressed; if the result was not a legitimate single character constant, then the complaint should be produced. (On my test case - admittedly a torture test - CPP yields 13 problems, mostly related to the one I'm complaining about, where SCC correctly yields 2.)

(I observe that the '-P' manages to suppress a '#line' directive in the output that appears when the option is omitted.)