Message ID | 1478242438.1924.31.camel@perches.com |
---|---|
State | Not Applicable, archived |
Delegated to: | David Miller |
Headers | show |
Hi, On 04.11.2016 07:53, Joe Perches wrote: > > CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest > #446: FILE: drivers/net/ethernet/ethoc.c:446: > + int size = bd.stat >> 16; > + struct sk_buff *skb; > should not this case be valid? Optically the longer line is already before the shorter. I think that the whole point in using this reverse xmas tree ordering is to have the code optically tidied up and not to enforce ordering between variable name lengths. Regards, Lino
From: Lino Sanfilippo <lsanfil@marvell.com> Date: Fri, 4 Nov 2016 12:01:17 +0100 > Hi, > > On 04.11.2016 07:53, Joe Perches wrote: >> >> CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to >> shortest >> #446: FILE: drivers/net/ethernet/ethoc.c:446: >> + int size = bd.stat >> 16; >> + struct sk_buff *skb; >> > > should not this case be valid? Optically the longer line is already > before the shorter. > I think that the whole point in using this reverse xmas tree ordering > is to have > the code optically tidied up and not to enforce ordering between > variable name lengths. That's correct.
On 11/03/16 23:53, Joe Perches wrote: > On Thu, 2016-11-03 at 15:58 -0400, David Miller wrote: >> From: Madalin Bucur <madalin.bucur@nxp.com> >> Date: Wed, 2 Nov 2016 22:17:26 +0200 >> >>> This introduces the Freescale Data Path Acceleration Architecture >>> +static inline size_t bpool_buffer_raw_size(u8 index, u8 cnt) >>> +{ >>> + u8 i; >>> + size_t res = DPAA_BP_RAW_SIZE / 2; >> >> Always order local variable declarations from longest to shortest line, >> also know as Reverse Christmas Tree Format. > > I think this declaration sorting order is misguided but > here's a possible change to checkpatch adding a test for it > that does this test just for net/ and drivers/net/ I agree with the misguided part. That's not actually in CodingStyle AFAICT. Where did this come from? thanks.
On Fri, 2016-11-04 at 11:07 -0400, David Miller wrote: > From: Lino Sanfilippo <lsanfil@marvell.com> > > On 04.11.2016 07:53, Joe Perches wrote: > >> CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to > >> shortest > >> #446: FILE: drivers/net/ethernet/ethoc.c:446: > >> + int size = bd.stat >> 16; > >> + struct sk_buff *skb; > > should not this case be valid? Optically the longer line is already > > before the shorter. > > I think that the whole point in using this reverse xmas tree ordering > > is to have > > the code optically tidied up and not to enforce ordering between > > variable name lengths. > > That's correct. And also another reason the whole reverse xmas tree automatic declaration layout concept is IMO dubious. Basically, you're looking not at the initial ordering of automatics as important, but helping find a specific automatic when reversing from reading code is not always correct. Something like: static void function{args,...) { [longish list of reverse xmas tree identifiers...] struct foo *bar = longish_function(args, ...); struct foobarbaz *qux; [more identifers] [multiple screenfuls of code later...) new_function(..., bar, ...); [more code...] } and the reverse xmas tree helpfulness of looking up the type of bar is neither obvious nor easy. My preference would be for a bar that serves coffee and alcohol.
On Fri, Nov 04, 2016 at 10:05:15AM -0700, Randy Dunlap wrote: > On 11/03/16 23:53, Joe Perches wrote: > > On Thu, 2016-11-03 at 15:58 -0400, David Miller wrote: > >> From: Madalin Bucur <madalin.bucur@nxp.com> > >> Date: Wed, 2 Nov 2016 22:17:26 +0200 > >> > >>> This introduces the Freescale Data Path Acceleration Architecture > >>> +static inline size_t bpool_buffer_raw_size(u8 index, u8 cnt) > >>> +{ > >>> + u8 i; > >>> + size_t res = DPAA_BP_RAW_SIZE / 2; > >> > >> Always order local variable declarations from longest to shortest line, > >> also know as Reverse Christmas Tree Format. > > > > I think this declaration sorting order is misguided but > > here's a possible change to checkpatch adding a test for it > > that does this test just for net/ and drivers/net/ > > I agree with the misguided part. > That's not actually in CodingStyle AFAICT. Where did this come from? > > > thanks. > -- > ~Randy This puzzles me. The CodingStyle gives some pretty reasonable rationales for coding style over above the "it's easier to read if it all looks the same". I can see rationales for other approaches (and I am not proposing any of these): alphabetic order Easier to search for declarations complex to simple As in, structs and unions, pointers to simple data (int, char), simple data. It seems like I can deduce the simple types from usage, but more complex I need to know things like the particular structure. group by usage Mirror the ontological locality in the code Do we have a basis for thinking this is easier or more consistent than any other approach?
On 04.11.2016 18:44, Joe Perches wrote: > On Fri, 2016-11-04 at 11:07 -0400, David Miller wrote: >> From: Lino Sanfilippo <lsanfil@marvell.com> >> > On 04.11.2016 07:53, Joe Perches wrote: >> >> CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to >> >> shortest >> >> #446: FILE: drivers/net/ethernet/ethoc.c:446: >> >> + int size = bd.stat >> 16; >> >> + struct sk_buff *skb; >> > should not this case be valid? Optically the longer line is already >> > before the shorter. >> > I think that the whole point in using this reverse xmas tree ordering >> > is to have >> > the code optically tidied up and not to enforce ordering between >> > variable name lengths. >> >> That's correct. > > And also another reason the whole reverse xmas tree > automatic declaration layout concept is IMO dubious. > > Basically, you're looking not at the initial ordering > of automatics as important, but helping find a specific > automatic when reversing from reading code is not always > correct. > > Something like: > > static void function{args,...) > { > [longish list of reverse xmas tree identifiers...] > struct foo *bar = longish_function(args, ...); > struct foobarbaz *qux; > [more identifers] > > [multiple screenfuls of code later...) > > new_function(..., bar, ...); > > [more code...] > } > > and the reverse xmas tree helpfulness of looking up the > type of bar is neither obvious nor easy. > In this case it is IMHO rather the declaration + initialization that makes "bar" hard to find at one glance, not the use of RXT. You could do something like [longish list of reverse xmas tree identifiers...] struct foobarbaz *qux; struct foo *bar; bar = longish_function(args, ...); to increase readability. Personally I find it more readable to always use a separate line for initializations by means of functions (regardless of whether the RXT scheme is used or not). > My preference would be for a bar that serves coffee and alcohol. > At least a bar like this should not be too hard to find :) Regards, Lino
Joe Perches <joe@perches.com> writes: > On Thu, 2016-11-03 at 15:58 -0400, David Miller wrote: >> From: Madalin Bucur <madalin.bucur@nxp.com> >> Date: Wed, 2 Nov 2016 22:17:26 +0200 >> >> > This introduces the Freescale Data Path Acceleration Architecture >> > +static inline size_t bpool_buffer_raw_size(u8 index, u8 cnt) >> > +{ >> > + u8 i; >> > + size_t res = DPAA_BP_RAW_SIZE / 2; >> >> Always order local variable declarations from longest to shortest line, >> also know as Reverse Christmas Tree Format. > > I think this declaration sorting order is misguided but > here's a possible change to checkpatch adding a test for it > that does this test just for net/ and drivers/net/ And arch/powerpc too please. cheers
From: Lino Sanfilippo > Sent: 04 November 2016 20:07 ... > In this case it is IMHO rather the declaration + initialization that makes > "bar" hard to find at one glance, not the use of RXT. You could do something like > > [longish list of reverse xmas tree identifiers...] > struct foobarbaz *qux; > struct foo *bar; > > bar = longish_function(args, ...); > > to increase readability. > > Personally I find it more readable to always use a separate line for initializations > by means of functions (regardless of whether the RXT scheme is used or not). I find it best to only use initialisers for 'variables' that are (mostly) constant. If something need to be set to NULL in case a search fails, set it to NULL just before the loop. Don't put initialisation on the declaration 'because you can'. Difficulty in spotting the type of a variable is why (IMHO) you should but all declarations at the top of a function (except, maybe, temporaries needed for a few lines). David
scripts/checkpatch.pl | 70 ++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 56 insertions(+), 14 deletions(-) diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index fdacd759078e..dd344ac77cb8 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -2114,6 +2114,29 @@ sub pos_last_openparen { return length(expand_tabs(substr($line, 0, $last_openparen))) + 1; } +sub get_decl { + my ($line) = @_; + + # typical declarations + if ($line =~ /^\+\s+($Declare\s*$Ident)\s*[=,;:\[]/) { + return $1; + } + # function pointer declarations + if ($line =~ /^\+\s+($Declare\s*\(\s*\*\s*$Ident\s*\))\s*[=,;:\[\(]/) { + return $1; + } + # foo bar; where foo is some local typedef or #define + if ($line =~ /^\+\s+($Ident(?:\s+|\s*\*\s*)$Ident)\s*[=,;\[]/) { + return $1; + } + # known declaration macros + if ($line =~ /^\+\s+$(declaration_macros)/) { + return $1; + } + + return undef; +} + sub process { my $filename = shift; @@ -3063,9 +3086,7 @@ sub process { $last_blank_line = $linenr; } -# check for missing blank lines after declarations - if ($sline =~ /^\+\s+\S/ && #Not at char 1 - # actual declarations + my $prev_decl = ($prevline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ || # function pointer declarations $prevline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ || @@ -3078,25 +3099,30 @@ sub process { # other possible extensions of declaration lines $prevline =~ /(?:$Compare|$Assignment|$Operators)\s*$/ || # not starting a section or a macro "\" extended line - $prevline =~ /(?:\{\s*|\\)$/) && - # looks like a declaration - !($sline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ || + $prevline =~ /(?:\{\s*|\\)$/); + my $sline_decl = + $sline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ || # function pointer declarations - $sline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ || + $sline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ || # foo bar; where foo is some local typedef or #define - $sline =~ /^\+\s+$Ident(?:\s+|\s*\*\s*)$Ident\s*[=,;\[]/ || + $sline =~ /^\+\s+$Ident(?:\s+|\s*\*\s*)$Ident\s*[=,;\[]/ || # known declaration macros - $sline =~ /^\+\s+$declaration_macros/ || + $sline =~ /^\+\s+$declaration_macros/ || # start of struct or union or enum - $sline =~ /^\+\s+(?:union|struct|enum|typedef)\b/ || + $sline =~ /^\+\s+(?:union|struct|enum|typedef)\b/ || # start or end of block or continuation of declaration - $sline =~ /^\+\s+(?:$|[\{\}\.\#\"\?\:\(\[])/ || + $sline =~ /^\+\s+(?:$|[\{\}\.\#\"\?\:\(\[])/ || # bitfield continuation - $sline =~ /^\+\s+$Ident\s*:\s*\d+\s*[,;]/ || + $sline =~ /^\+\s+$Ident\s*:\s*\d+\s*[,;]/ || # other possible extensions of declaration lines - $sline =~ /^\+\s+\(?\s*(?:$Compare|$Assignment|$Operators)/) && + $sline =~ /^\+\s+\(?\s*(?:$Compare|$Assignment|$Operators)/; + +# check for missing blank lines after declarations + if ($sline =~ /^\+\s+\S/ && #Not at char 1 + # actual declarations + $prev_decl && !$sline_decl && # indentation of previous and current line are the same - (($prevline =~ /\+(\s+)\S/) && $sline =~ /^\+$1\S/)) { + ($prevline =~ /\+(\s+)\S/ && $sline =~ /^\+$1\S/)) { if (WARN("LINE_SPACING", "Missing a blank line after declarations\n" . $hereprev) && $fix) { @@ -3104,6 +3130,22 @@ sub process { } } +# check for reverse christmas tree declarations in net/ and drivers/net/ + if ($realfile =~ m@^(?:drivers/net/|net/)@ && + $sline =~ /^\+\s+\S/ && #Not at char 1 + # actual declarations + $prev_decl && $sline_decl && + # indentation of previous and current line are the same + (($prevline =~ /\+(\s+)\S/) && $sline =~ /^\+$1\S/)) { + my $p = get_decl($prevline); + my $l = get_decl($sline); + if (defined($p) && defined($l) && length($p) < length($l) && + CHK("REVERSE_XMAS_TREE", + "Prefer ordering declarations longest to shortest\n" . $hereprev) && + $fix) { + } + } + # check for spaces at the beginning of a line. # Exceptions: # 1) within comments