checkhf: handle C++-style comments

"tools/checkhf.pl epan/dissectors/packet-umts_fp.c" gave this error:

    Complex regular subexpression recursion limit (32766) exceeded at tools/checkhf.pl line 273.

This is caused by the comment "// ... Indicator's ..." which failed to
match the single-quoted string and caused "catastrophic backtracking".
Solution to fix this case is to disallow unescaped newlines (add "\n" to
the negated character class). Additionally, add logic to remove
C++-style comments for completeness.

Tested against all epan/dissectors/packet-*.c files, the only difference
in output is this umts_fp case, the running time has not regressed.

Change-Id: I7b43e01e1580acf831c0485513135b613bb02e8b
Reported-by: Joerg Mayer
Reviewed-on: https://code.wireshark.org/review/20965
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Reviewed-by: Michael Mann <mmann78@netscape.net>

1 files changed, 21 insertions, 9 deletions

diff --git a/tools/checkhf.pl b/tools/checkhf.pl
index 93bcb316a5..5059374474 100755
--- a/tools/checkhf.pl
+++ b/tools/checkhf.pl
@@ -235,6 +235,18 @@ sub remove_blank_lines {
     return;
 }
 
+sub get_quoted_str_regex {
+    # A regex which matches double-quoted strings.
+    #    's' modifier added so that strings containing a 'line continuation'
+    #    ( \ followed by a new-line) will match.
+    my $double_quoted_str = qr{ (?: ["] (?: \\. | [^\"\\\n])* ["]) }xmso;
+
+    # A regex which matches single-quoted strings.
+    my $single_quoted_str = qr{ (?: ['] (?: \\. | [^\'\\\n])* [']) }xmso;
+
+    return qr{ $double_quoted_str | $single_quoted_str }xmso;
+}
+
 # ------------
 # action:  remove comments from input string
 # arg:     code_ref, filename
@@ -250,6 +262,13 @@ sub remove_comments {
 
     ${$code_ref} =~ s{ $c_comment_regex } {}xmsog;
 
+    # Remove single-line C++-style comments. Be careful not to break up strings
+    # like "coap://", so match double quoted strings, single quoted characters,
+    # division operator and other characters before the actual "//" comment.
+    my $quoted_str = get_quoted_str_regex();
+    my $cpp_comment_regex = qr{ ^((?: $quoted_str | /(?!/) | [^'"/\n] )*) // .*$ }xm;
+    ${$code_ref} =~ s{ $cpp_comment_regex } { $1 }xmg;
+
     ($debug == 1) && print "==> After Remove Comments: code: [$filename]\n${$code_ref}\n===<\n";
 
     return;
@@ -262,15 +281,8 @@ sub remove_comments {
 sub remove_quoted_strings {
     my ($code_ref, $filename) = @_;
 
-    # A regex which matches double-quoted strings.
-    #    's' modifier added so that strings containing a 'line continuation'
-    #    ( \ followed by a new-line) will match.
-    my $double_quoted_str = qr{ (?: ["] (?: \\. | [^\"\\])* ["]) }xmso;
-
-    # A regex which matches single-quoted strings.
-    my $single_quoted_str = qr{ (?: ['] (?: \\. | [^\'\\])* [']) }xmso;
-
-    ${$code_ref} =~ s{ $double_quoted_str | $single_quoted_str } {}xmsog;
+    my $quoted_str = get_quoted_str_regex();
+    ${$code_ref} =~ s{ $quoted_str } {}xmsog;
 
     ($debug == 1) && print "==> After Remove quoted strings: code: [$filename]\n${$code_ref}\n===<\n";