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Subject[PATCH] cvt_fallthrough: A tool to convert /* fallthrough */ comments to fallthrough;
Date
Convert /* fallthrough */ style comments to the pseudo-keyword fallthrough
to allow clang 10 and higher to work at finding missing fallthroughs too.

Requires a git repository and overwrites the input files.

Typical command use:
./scripts/cvt_fallthrough.pl <path|file>

i.e.:

$ ./scripts/cvt_fallthrough.pl block
converts all files in block and its subdirectories
$ ./scripts/cvt_fallthrough.pl drivers/net/wireless/zydas/zd1201.c
converts a single file

A fallthrough comment with additional comments is converted akin to:

- /* fall through - maybe userspace knows this conn_id. */
+ fallthrough; /* maybe userspace knows this conn_id */

A fallthrough comment or fallthrough; between successive case statements
is deleted.

e.g.:

case FOO:
/* fallthrough */ (or fallthrough;)
case BAR:

is converted to:

case FOO:
case BAR:

Signed-off-by: Joe Perches <joe@perches.com>
---
scripts/cvt_fallthrough.pl | 215 +++++++++++++++++++++++++++++++++++++
1 file changed, 215 insertions(+)
create mode 100755 scripts/cvt_fallthrough.pl

diff --git a/scripts/cvt_fallthrough.pl b/scripts/cvt_fallthrough.pl
new file mode 100755
index 000000..6585e4
--- /dev/null
+++ b/scripts/cvt_fallthrough.pl
@@ -0,0 +1,215 @@
+#!/usr/bin/perl -w
+
+# script to modify /* fallthrough */ style comments to fallthrough;
+# use: perl cvt_fallthrough.pl <paths|files>
+# e.g.: perl cvtfallthrough.pl drivers/net/ethernet/intel
+
+use strict;
+
+my $P = $0;
+my $modified = 0;
+my $quiet = 0;
+
+sub expand_tabs {
+ my ($str) = @_;
+
+ my $res = '';
+ my $n = 0;
+ for my $c (split(//, $str)) {
+ if ($c eq "\t") {
+ $res .= ' ';
+ $n++;
+ for (; ($n % 8) != 0; $n++) {
+ $res .= ' ';
+ }
+ next;
+ }
+ $res .= $c;
+ $n++;
+ }
+
+ return $res;
+}
+
+my $args = join(" ", @ARGV);
+my $output = `git ls-files -- $args`;
+my @files = split("\n", $output);
+
+foreach my $file (@files) {
+ my $f;
+ my $cvt = 0;
+ my $del = 0;
+ my $text;
+
+# read the file
+
+ next if ((-d $file));
+
+ open($f, '<', $file)
+ or die "$P: Can't open $file for read\n";
+ $text = do { local($/) ; <$f> };
+ close($f);
+
+ next if ($text eq "");
+
+ # for style:
+
+ # /* <fallthrough comment> */
+ # case FOO:
+
+ # while (comment has fallthrough and next non-blank, non-continuation line is (case or default:)) {
+ # remove newline, whitespace before, fallthrough comment and whitespace after
+ # insert newline, adjusted spacing and fallthrough; newline
+ # }
+
+ my $count = 0;
+ my @fallthroughs = (
+ 'fallthrough',
+ '@fallthrough@',
+ 'lint -fallthrough[ \t]*',
+ '[ \t.!]*(?:ELSE,? |INTENTIONAL(?:LY)? )?',
+ 'intentional(?:ly)?[ \t]*fall(?:(?:s | |-)[Tt]|t)hr(?:ough|u|ew)',
+ '(?:else,?\s*)?FALL(?:S | |-)?THR(?:OUGH|U|EW)[ \t.!]*(?:-[^\n\r]*)?',
+ '[ \t.!]*(?:Else,? |Intentional(?:ly)? )?',
+ 'Fall(?:(?:s | |-)[Tt]|t)hr(?:ough|u|ew)[ \t.!]*(?:-[^\n\r]*)?',
+ '[ \t.!]*(?:[Ee]lse,? |[Ii]ntentional(?:ly)? )?',
+ 'fall(?:s | |-)?thr(?:ough|u|ew)[ \t.!]*(?:-[^\n\r]*)?',
+ );
+ do {
+ $count = 0;
+ pos($text) = 0;
+ foreach my $ft (@fallthroughs) {
+ my $regex = '(((?:[ \t]*\n)*[ \t]*)(/\*\s*(?!\*/)?\b' . "$ft" . '\s*(?!\*/)?\*/(?:[ \t]*\n)*)([ \t]*))(?:case\s+|default\s*:)';
+
+ while ($text =~ m{${regex}}i) {
+ my $all_but_case = $1;
+ my $space_before = $2;
+ my $fallthrough = $3;
+ my $space_after = $4;
+ my $pos_before = $-[1];
+ my $pos_after = $+[3];
+
+ # try to maintain any additional comment on the same line
+ my $comment = "";
+ if ($regex =~ /\\r/) {
+ $comment = $fallthrough;
+ $comment =~ s@^/\*\s*@@;
+ $comment =~ s@\s*\*/\s*$@@;
+ $comment =~ s@^\s*(?:intentional(?:ly)?\s+|else,?\s*)?fall[s\-]*\s*thr(?:ough|u|ew)[\s\.\-]*@@i;
+ $comment =~ s@\s+$@@;
+ $comment =~ s@\.*$@@;
+ $comment = "\t/* $comment */" if ($comment ne "");
+ }
+ substr($text, $pos_before, $pos_after - $pos_before, "");
+ substr($text, $pos_before, 0, "\n${space_after}\tfallthrough;${comment}\n");
+ pos($text) = $pos_before;
+ $count++;
+ }
+ }
+ $cvt += $count;
+ } while ($count > 0);
+
+ # Reset the fallthroughs types to a single regex
+
+ @fallthroughs = (
+ 'fall(?:(?:s | |-)[Tt]|t)hr(?:ough|u|ew)'
+ );
+
+ # Convert the // <fallthrough> style comments followed by case/default:
+
+ do {
+ $count = 0;
+ pos($text) = 0;
+ foreach my $ft (@fallthroughs) {
+ my $regex = '(((?:[ \t]*\n)*[ \t]*)(//[ \t]*(?!\n)?\b' . "$ft" . '[ \t]*(?!\n)?\n(?:[ \t]*\n)*)([ \t]*))(?:case\s+|default\s*:)';
+ while ($text =~ m{${regex}}i) {
+ my $all_but_case = $1;
+ my $space_before = $2;
+ my $fallthrough = $3;
+ my $space_after = $4;
+ my $pos_before = $-[1];
+ my $pos_after = $+[3];
+
+ substr($text, $pos_before, $pos_after - $pos_before, "");
+ substr($text, $pos_before, 0, "\n${space_after}\tfallthrough;\n");
+ pos($text) = $pos_before;
+ $count++;
+ }
+ }
+ $cvt += $count;
+ } while ($count > 0);
+
+ # Convert /* fallthrough */ comment macro lines with trailing \
+
+ do {
+ $count = 0;
+ pos($text) = 0;
+ foreach my $ft (@fallthroughs) {
+ my $regex = '((?:[ \t]*\\\\\n)*([ \t]*)(/\*[ \t]*\b' . "$ft" . '[ \t]*\*/)([ \t]*))\\\\\n*([ \t]*(?:case\s+|default\s*:))';
+
+ while ($text =~ m{${regex}}i) {
+ my $all_but_case = $1;
+ my $space_before = $2;
+ my $fallthrough = $3;
+ my $space_after = $4;
+ my $pos_before = $-[2];
+ my $pos_after = $+[4];
+
+ my $oldline = "${space_before}${fallthrough}${space_after}";
+ my $len = length(expand_tabs($oldline));
+
+ my $newline = "${space_before}fallthrough;${space_after}";
+ $newline .= "\t" while (length(expand_tabs($newline)) < $len);
+
+ substr($text, $pos_before, $pos_after - $pos_before, "");
+ substr($text, $pos_before, 0, "$newline");
+ pos($text) = $pos_before;
+ $count++;
+ }
+ }
+ $cvt += $count;
+ } while ($count > 0);
+
+ # delete any unnecessary fallthrough; between successive cases and default:
+
+ do {
+ pos($text) = 0;
+ $count = $text =~ s/(case\s+\w+\s*:\n)[ \t]*fallthrough;\n((?:\s*default\s*:|\s*case\s+\w+\s*:))/$1$2/;
+ $del += $count;
+ } while ($count > 0);
+
+# write the file if something was changed
+
+ if ($cvt > 0 || $del > 0) {
+ $modified = 1;
+
+ open($f, '>', $file)
+ or die "$P: Can't open $file for write\n";
+ print $f $text;
+ close($f);
+
+ if (!$quiet) {
+ print "fallthroughs:";
+ print " converted: $cvt" if ($cvt > 0);
+ print " deleted: $del" if ($del > 0);
+ print " $file\n";
+ }
+ }
+}
+
+if ($modified && !$quiet) {
+ print <<EOT;
+
+Warning: these changes may not be correct.
+
+These changes should be carefully reviewed manually and not combined with
+any functional changes.
+
+Compile, build and test your changes.
+
+You should understand and be responsible for all object changes.
+
+Make sure you read Documentation/SubmittingPatches before sending
+any changes to reviewers, maintainers or mailing lists.
+EOT
+}
--
2.24.0
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