Thread (12 messages) 12 messages, 6 authors, 2019-10-12

Re: [PATCH 0/4] treewide: Add 'fallthrough' pseudo-keyword

From: Joe Perches <joe@perches.com>
Date: 2019-10-11 17:43:11
Also in: linux-doc, linux-sctp, lkml
Subsystem: the rest · Maintainer: Linus Torvalds

On Fri, 2019-10-11 at 09:29 -0700, Linus Torvalds wrote:
On Sat, Oct 5, 2019 at 9:46 AM Joe Perches [off-list ref] wrote:
quoted
Add 'fallthrough' pseudo-keyword to enable the removal of comments
like '/* fallthrough */'.
I applied patches 1-3 to my tree just to make it easier for people to
start doing this. Maybe some people want to do the conversion on their
own subsystem rather than with a global script, but even if not, this
looks better as a "prepare for the future" series and I feel that if
we're doing the "fallthrough" thing eventually, the sooner we do the
prepwork the better.

I'm a tiny bit worried that the actual conversion is just going to
cause lots of pain for the stable people, but I'll not worry about it
_too_ much. If the stable people decide that it's too painful for them
to deal with the comment vs keyword model, they may want to backport
these three patches too.
Shouldn't a conversion script be public somewhere?
The old cvt_style script could be reduced to something like the below.

From: Joe Perches <joe@perches.com>
Date: Fri, 11 Oct 2019 10:34:04 -0700
Subject: [PATCH] scripts:cvt_fallthrough.pl: Add script to convert /* fallthrough */ comments

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 this overwrites the input sources.

Run with a path like:

    ./scripts/cvt_fallthrough.pl block

and all files in the path will be converted or a specific file like:

   ./scripts/cvt_fallthrough.pl drivers/net/wireless/zydas/zd1201.c

Signed-off-by: Joe Perches <joe@perches.com>
---
 scripts/cvt_fallthrough.pl | 201 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 201 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 000000000000..013379464f86
--- /dev/null
+++ b/scripts/cvt_fallthrough.pl
@@ -0,0 +1,201 @@
+#!/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 $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);
+
+# write the file if something was changed
+
+    if ($cvt > 0) {
+	$modified = 1;
+
+	open($f, '>', $file)
+	    or die "$P: Can't open $file for write\n";
+	print $f $text;
+	close($f);
+
+	print "fallthroughs: $cvt	$file\n" if (!$quiet);
+    }
+}
+
+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
+}
-- 
2.15.0



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