Re: [PATCH -v2] scipts/tags.sh: Add custom sort order

[Masahiro Yamada <masahiroy@kernel.org>]

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On Fri, Aug 7, 2020 at 2:28 AM <peterz@infradead.org> wrote:
>
>
> One long standing annoyance I have with using vim-tags is that our tags
> file is not properly sorted. That is, the sorting exhuberant Ctags does
> is only on the tag itself.
>
> The problem with that is that, for example, the tag 'mutex' appears a
> mere 505 times, 492 of those are structure members. However it is _far_
> more likely that someone wants the struct definition when looking for
> the mutex tag than any of those members. However, due to the nature of
> the sorting, the struct definition will not be first.
>
> So add a script that does a custom sort of the tags file, taking the tag
> kind into account.
>
> The kind ordering is roughly: 'type', 'function', 'macro', 'enum', rest.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> Changes since v1:
>  - removed the need for tags.unsorted by using a pipe
>
> Due to this change 'make tags' is now actually faster than it was before
> due to less sorting.
>
>  scripts/sort-tags.awk | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  scripts/tags.sh       | 11 +++++--
>  2 files changed, 87 insertions(+), 3 deletions(-)
>
> diff --git a/scripts/sort-tags.awk b/scripts/sort-tags.awk
> new file mode 100755
> index 000000000000..1eb50406c9d3
> --- /dev/null
> +++ b/scripts/sort-tags.awk
> @@ -0,0 +1,79 @@
> +#!/usr/bin/awk -f
> +
> +# $ ctags --list-kinds
> +# C
> +#   c  classes
> +#   s  structure names
> +#   t  typedefs
> +#   g  enumeration names
> +#   u  union names
> +#   n  namespaces
> +
> +#   f  function definitions
> +#   p  function prototypes [off]
> +#   d  macro definitions
> +
> +#   e  enumerators (values inside an enumeration)
> +#   m  class, struct, and union members
> +#   v  variable definitions
> +
> +#   l  local variables [off]
> +#   x  external and forward variable declarations [off]
> +
> +BEGIN {
> +       FS = "\t"
> +
> +       sort = "LC_ALL=C sort"
> +
> +       # our sort order for C kinds:
> +       order["c"] = "A"
> +       order["s"] = "B"
> +       order["t"] = "C"
> +       order["g"] = "D"
> +       order["u"] = "E"
> +       order["n"] = "F"
> +       order["f"] = "G"
> +       order["p"] = "H"
> +       order["d"] = "I"
> +       order["e"] = "J"
> +       order["m"] = "K"
> +       order["v"] = "L"
> +       order["l"] = "M"
> +       order["x"] = "N"
> +}
> +
> +# pass through header
> +/^!_TAG/ {
> +       print $0
> +       next
> +}
> +
> +{
> +       # find 'kinds'
> +       for (i = 1; i <= NF; i++) {
> +               if ($i ~ /;"$/) {
> +                       kind = $(i+1)
> +                       break;
> +               }
> +       }
> +
> +       # create sort key
> +       if (order[kind])
> +               key = $1 order[kind];
> +       else
> +               key = $1 "Z";
> +
> +       # get it sorted
> +       print key "\t" $0 |& sort
> +}
> +
> +END {
> +       close(sort, "to")
> +       while ((sort |& getline) > 0) {
> +               # strip key
> +               sub(/[^[:space:]]*[[:space:]]*/, "")
> +               print $0
> +       }
> +       close(sort)
> +}
> +
> diff --git a/scripts/tags.sh b/scripts/tags.sh
> index 4e18ae5282a6..51087c3d8b1e 100755
> --- a/scripts/tags.sh
> +++ b/scripts/tags.sh
> @@ -251,8 +251,10 @@ setup_regex()
>
>  exuberant()
>  {
> +       (
> +
>         setup_regex exuberant asm c
> -       all_target_sources | xargs $1 -a                        \
> +       all_target_sources | xargs $1                           \
>         -I __initdata,__exitdata,__initconst,__ro_after_init    \
>         -I __initdata_memblock                                  \
>         -I __refdata,__attribute,__maybe_unused,__always_unused \
> @@ -266,12 +268,15 @@ exuberant()
>         -I DEFINE_TRACE,EXPORT_TRACEPOINT_SYMBOL,EXPORT_TRACEPOINT_SYMBOL_GPL \
>         -I static,const                                         \
>         --extra=+fq --c-kinds=+px --fields=+iaS --langmap=c:+.h \
> +       --sort=no -o -                                          \
>         "${regex[@]}"
>
>         setup_regex exuberant kconfig
> -       all_kconfigs | xargs $1 -a                              \
> -       --langdef=kconfig --language-force=kconfig "${regex[@]}"
> +       all_kconfigs | xargs $1                                 \
> +       --langdef=kconfig --language-force=kconfig --sort=no    \
> +       -o - "${regex[@]}"
>
> +       ) | scripts/sort-tags.awk > tags
>  }
>
>  emacs()


Sorry for the long delay.

First, this patch breaks 'make TAGS'
if 'etags' is a symlink to exuberant ctags.


masahiro@oscar:~/ref/linux$ etags --version
Exuberant Ctags 5.9~svn20110310, Copyright (C) 1996-2009 Darren Hiebert
  Addresses: <dhiebert@users.sourceforge.net>, http://ctags.sourceforge.net
  Optional compiled features: +wildcards, +regex

masahiro@oscar:~/ref/linux$ make TAGS
  GEN     TAGS
etags: Warning: include/linux/seqlock.h:738: null expansion of name pattern "\2"
sed: can't read TAGS: No such file or directory
make: *** [Makefile:1820: TAGS] Error 2




The reason is the hard-coded ' > tags',
and easy to fix.



But, honestly, I am not super happy about this patch.

Reason 1
  In my understanding, sorting by the tag kind only works
  for ctags. My favorite editor is emacs.
  (Do not get me wrong. I do not intend emacs vs vi war).
  So, I rather do 'make TAGS' instead of 'make tags',
  but this solution would not work for etags because
  etags has a different format.
  So, I'd rather want to see a more general solution.

Reason 2
  We would have more messy code, mixing two files/languages



When is it useful to tag structure members?

If they are really annoying, why don't we delete them
instead of moving them to the bottom of the tag file?



I attached an alternative solution,
and wrote up my thoughts in the log.

What do you think?


-- 
Best Regards
Masahiro Yamada

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From 1a003fce7e4f8460ef3256fb5d958fb5c6cc631e Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <masahiroy@kernel.org>
Date: Wed, 2 Sep 2020 21:49:59 +0900
Subject: [PATCH] scripts/tags.sh: remove m, v, x tag kinds from exuberant tags

Exuberant Ctags supports the following kinds of tags:

  $ ctags --list-kinds=c
  c  classes
  d  macro definitions
  e  enumerators (values inside an enumeration)
  f  function definitions
  g  enumeration names
  l  local variables [off]
  m  class, struct, and union members
  n  namespaces
  p  function prototypes [off]
  s  structure names
  t  typedefs
  u  union names
  v  variable definitions
  x  external and forward variable declarations [off]

This commit excludes 'm', 'v', and 'x'.

Peter Zijlstra states:
"The problem with that is that, for example, the tag 'mutex' appears a
mere 505 times, 492 of those are structure members. However it is _far_
more likely that someone wants the struct definition when looking for
the mutex tag than any of those members."
(https://lkml.org/lkml/2020/8/6/512")

So, 'm' is rather annoying than useful. For the same reason, it seems
better to turn off 'v'.

You may argue about the criteria, but we need to draw a line somewhere
to make it reasonable for the majority of people.

We flipped 'p' and 'x' in the past:

[1] commit f6333eb4e788 ("kbuild: Add ctags support for function
    prototypes and external variable declarations") added 'p' and 'x',
    but did not explain when they are actually useful.

[2] commit 7db86dc97fb0 ("ctags: usability fix") removed 'p' and 'x',
    stating both of them make no real sense.

[3] commit 0a18a9386c05 ("tags: put function prototypes back!")
    re-added 'p' and 'x', but the commit log only mentioned 'p'.

OK, [3] clearly explained why 'p' is useful, but turned --c-kinds=+px
into --c-kinds=-px. So, 'x' was also (accidentally?) disabled. I think
it should have been --c-kinds=+p-x, or more simply --c-kinds=+p since
'x' is off by default.

It seems a bug of [3], so I disabled 'x' to get back the pre-[3]
behavior.

'make tags' and 'make TAGS' will run faster, create much smaller tags
if Ctags is exuberant.

Reviewed-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---
 scripts/tags.sh | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/scripts/tags.sh b/scripts/tags.sh
index 32d3f53af10b..440f4ecad43b 100755
--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@@ -179,19 +179,6 @@ regex_c=(
 	'/^DEF_PCI_AC_\(\|NO\)RET(\([[:alnum:]_]*\).*/\2/'
 	'/^PCI_OP_READ(\(\w*\).*[1-4])/pci_bus_read_config_\1/'
 	'/^PCI_OP_WRITE(\(\w*\).*[1-4])/pci_bus_write_config_\1/'
-	'/\<DEFINE_\(RT_MUTEX\|MUTEX\|SEMAPHORE\|SPINLOCK\)(\([[:alnum:]_]*\)/\2/v/'
-	'/\<DEFINE_\(RAW_SPINLOCK\|RWLOCK\|SEQLOCK\)(\([[:alnum:]_]*\)/\2/v/'
-	'/\<DECLARE_\(RWSEM\|COMPLETION\)(\([[:alnum:]_]\+\)/\2/v/'
-	'/\<DECLARE_BITMAP(\([[:alnum:]_]*\)/\1/v/'
-	'/\(^\|\s\)\(\|L\|H\)LIST_HEAD(\([[:alnum:]_]*\)/\3/v/'
-	'/\(^\|\s\)RADIX_TREE(\([[:alnum:]_]*\)/\2/v/'
-	'/\<DEFINE_PER_CPU([^,]*, *\([[:alnum:]_]*\)/\1/v/'
-	'/\<DEFINE_PER_CPU_SHARED_ALIGNED([^,]*, *\([[:alnum:]_]*\)/\1/v/'
-	'/\<DECLARE_WAIT_QUEUE_HEAD(\([[:alnum:]_]*\)/\1/v/'
-	'/\<DECLARE_\(TASKLET\|WORK\|DELAYED_WORK\)(\([[:alnum:]_]*\)/\2/v/'
-	'/\(^\s\)OFFSET(\([[:alnum:]_]*\)/\2/v/'
-	'/\(^\s\)DEFINE(\([[:alnum:]_]*\)/\2/v/'
-	'/\<\(DEFINE\|DECLARE\)_HASHTABLE(\([[:alnum:]_]*\)/\2/v/'
 	'/\<DEFINE_ID\(R\|A\)(\([[:alnum:]_]\+\)/\2/'
 	'/\<DEFINE_WD_CLASS(\([[:alnum:]_]\+\)/\1/'
 	'/\<ATOMIC_NOTIFIER_HEAD(\([[:alnum:]_]\+\)/\1/'
@@ -255,7 +242,7 @@ exuberant()
 	-I EXPORT_SYMBOL,EXPORT_SYMBOL_GPL,ACPI_EXPORT_SYMBOL   \
 	-I DEFINE_TRACE,EXPORT_TRACEPOINT_SYMBOL,EXPORT_TRACEPOINT_SYMBOL_GPL \
 	-I static,const						\
-	--extra=+fq --c-kinds=+px --fields=+iaS --langmap=c:+.h \
+	--extra=+fq --c-kinds=+p-mv --fields=+iaS --langmap=c:+.h \
 	"${regex[@]}"
 
 	setup_regex exuberant kconfig
-- 
2.25.1