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From: Dan Williams <dan.j.williams@intel.com>
To: David Howells <dhowells@redhat.com>
Cc: Linux API <linux-api@vger.kernel.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-kbuild@vger.kernel.org
Subject: Re: [PATCH 09/11] UAPI: ndctl: Fix g++-unsupported initialisation in headers [ver #2]
Date: Tue, 25 Sep 2018 13:22:21 -0700	[thread overview]
Message-ID: <CAPcyv4jjxh955mWEubnGiENVQVeCcZ9YWv8YPBKfWMw-gh1z2w@mail.gmail.com> (raw)
In-Reply-To: <153622556444.14298.5971956747198405225.stgit@warthog.procyon.org.uk>

On Thu, Sep 6, 2018 at 2:19 AM David Howells <dhowells@redhat.com> wrote:
>
> The following code in the linux/ndctl header file:
>
>         static inline const char *nvdimm_bus_cmd_name(unsigned cmd)
>         {
>                 static const char * const names[] = {
>                         [ND_CMD_ARS_CAP] = "ars_cap",
>                         [ND_CMD_ARS_START] = "ars_start",
>                         [ND_CMD_ARS_STATUS] = "ars_status",
>                         [ND_CMD_CLEAR_ERROR] = "clear_error",
>                         [ND_CMD_CALL] = "cmd_call",
>                 };
>
>                 if (cmd < ARRAY_SIZE(names) && names[cmd])
>                         return names[cmd];
>                 return "unknown";
>         }
>
> is broken in a number of ways:
>
>  (1) ARRAY_SIZE() is not generally defined.
>
>  (2) g++ does not support "non-trivial" array initialisers fully yet.
>
>  (3) Every file that calls this function will acquire a copy of names[].
>
> The same goes for nvdimm_cmd_name().
>
> Fix all three by converting to a switch statement where each case returns a
> string.  That way if cmd is a constant, the compiler can trivially reduce it
> and, if not, the compiler can use a shared lookup table if it thinks that is
> more efficient.
>
> A better way would be to remove these functions and their arrays from the
> header entirely.
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Dan Williams <dan.j.williams@intel.com>

Acked-by: Dan Williams <dan.j.williams@intel.com>

...again let me know if you'll take this with g++ series or want me to
carry it directly.
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com>
To: David Howells <dhowells@redhat.com>
Cc: Linux API <linux-api@vger.kernel.org>,
	linux-kbuild@vger.kernel.org,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 09/11] UAPI: ndctl: Fix g++-unsupported initialisation in headers [ver #2]
Date: Tue, 25 Sep 2018 13:22:21 -0700	[thread overview]
Message-ID: <CAPcyv4jjxh955mWEubnGiENVQVeCcZ9YWv8YPBKfWMw-gh1z2w@mail.gmail.com> (raw)
In-Reply-To: <153622556444.14298.5971956747198405225.stgit@warthog.procyon.org.uk>

On Thu, Sep 6, 2018 at 2:19 AM David Howells <dhowells@redhat.com> wrote:
>
> The following code in the linux/ndctl header file:
>
>         static inline const char *nvdimm_bus_cmd_name(unsigned cmd)
>         {
>                 static const char * const names[] = {
>                         [ND_CMD_ARS_CAP] = "ars_cap",
>                         [ND_CMD_ARS_START] = "ars_start",
>                         [ND_CMD_ARS_STATUS] = "ars_status",
>                         [ND_CMD_CLEAR_ERROR] = "clear_error",
>                         [ND_CMD_CALL] = "cmd_call",
>                 };
>
>                 if (cmd < ARRAY_SIZE(names) && names[cmd])
>                         return names[cmd];
>                 return "unknown";
>         }
>
> is broken in a number of ways:
>
>  (1) ARRAY_SIZE() is not generally defined.
>
>  (2) g++ does not support "non-trivial" array initialisers fully yet.
>
>  (3) Every file that calls this function will acquire a copy of names[].
>
> The same goes for nvdimm_cmd_name().
>
> Fix all three by converting to a switch statement where each case returns a
> string.  That way if cmd is a constant, the compiler can trivially reduce it
> and, if not, the compiler can use a shared lookup table if it thinks that is
> more efficient.
>
> A better way would be to remove these functions and their arrays from the
> header entirely.
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Dan Williams <dan.j.williams@intel.com>

Acked-by: Dan Williams <dan.j.williams@intel.com>

...again let me know if you'll take this with g++ series or want me to
carry it directly.

WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
To: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-nvdimm
	<linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>,
	Linux Kernel Mailing List
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	linux-kbuild-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 09/11] UAPI: ndctl: Fix g++-unsupported initialisation in headers [ver #2]
Date: Tue, 25 Sep 2018 13:22:21 -0700	[thread overview]
Message-ID: <CAPcyv4jjxh955mWEubnGiENVQVeCcZ9YWv8YPBKfWMw-gh1z2w@mail.gmail.com> (raw)
In-Reply-To: <153622556444.14298.5971956747198405225.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>

On Thu, Sep 6, 2018 at 2:19 AM David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>
> The following code in the linux/ndctl header file:
>
>         static inline const char *nvdimm_bus_cmd_name(unsigned cmd)
>         {
>                 static const char * const names[] = {
>                         [ND_CMD_ARS_CAP] = "ars_cap",
>                         [ND_CMD_ARS_START] = "ars_start",
>                         [ND_CMD_ARS_STATUS] = "ars_status",
>                         [ND_CMD_CLEAR_ERROR] = "clear_error",
>                         [ND_CMD_CALL] = "cmd_call",
>                 };
>
>                 if (cmd < ARRAY_SIZE(names) && names[cmd])
>                         return names[cmd];
>                 return "unknown";
>         }
>
> is broken in a number of ways:
>
>  (1) ARRAY_SIZE() is not generally defined.
>
>  (2) g++ does not support "non-trivial" array initialisers fully yet.
>
>  (3) Every file that calls this function will acquire a copy of names[].
>
> The same goes for nvdimm_cmd_name().
>
> Fix all three by converting to a switch statement where each case returns a
> string.  That way if cmd is a constant, the compiler can trivially reduce it
> and, if not, the compiler can use a shared lookup table if it thinks that is
> more efficient.
>
> A better way would be to remove these functions and their arrays from the
> header entirely.
>
> Signed-off-by: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> cc: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

Acked-by: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

...again let me know if you'll take this with g++ series or want me to
carry it directly.

  reply	other threads:[~2018-09-25 20:22 UTC|newest]

Thread overview: 124+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-06  9:18 [RFC] UAPI: Check headers by compiling all together as C++ David Howells
2018-09-06  9:18 ` David Howells
2018-09-06  9:18 ` David Howells
2018-09-06  9:18 ` David Howells
2018-09-06  9:18 ` David Howells
     [not found] ` <153622549721.14298.8116794954073122489.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2018-09-06  9:18   ` [PATCH 01/11] UAPI: drm: Fix use of C++ keywords as structural members [ver #2] David Howells
2018-09-06  9:18     ` David Howells
2018-09-06  9:18 ` [PATCH 02/11] UAPI: keys: " David Howells
2018-09-06  9:18   ` David Howells
2018-09-06  9:18 ` [PATCH 03/11] UAPI: virtio_net: " David Howells
2018-09-06 15:02   ` Michael S. Tsirkin
2018-09-06 15:02   ` Michael S. Tsirkin
2018-09-06  9:18 ` David Howells
2018-09-06  9:18 ` [PATCH 04/11] UAPI: bcache: Fix use of embedded flexible array " David Howells
2018-09-06  9:18 ` [PATCH 05/11] UAPI: coda: Move kernel internals out of public view " David Howells
2018-09-06  9:18   ` David Howells
2018-09-06  9:19 ` [PATCH 06/11] coda: Move internal defs out of include/linux/ " David Howells
2018-09-06  9:19 ` [PATCH 07/11] UAPI: netfilter: Fix symbol collision issues " David Howells
2018-09-10 17:32   ` kbuild test robot
2018-09-10 17:32     ` kbuild test robot
2018-09-10 17:32     ` kbuild test robot
2018-09-28 13:07   ` [netfilter-core] " Pablo Neira Ayuso
2018-10-09 15:35   ` David Howells
2018-09-06  9:19 ` [PATCH 08/11] UAPI: nilfs2: Fix use of undefined byteswapping functions " David Howells
2018-09-06  9:19 ` [PATCH 09/11] UAPI: ndctl: Fix g++-unsupported initialisation in headers " David Howells
2018-09-06  9:19   ` David Howells
2018-09-06  9:19   ` David Howells
2018-09-25 20:22   ` Dan Williams [this message]
2018-09-25 20:22     ` Dan Williams
2018-09-25 20:22     ` Dan Williams
2018-09-06  9:19 ` [PATCH 10/11] UAPI: ndctl: Remove use of PAGE_SIZE " David Howells
2018-09-06  9:19   ` David Howells
2018-09-06  9:19   ` David Howells
2018-09-25 20:17   ` Dan Williams
2018-09-25 20:17     ` Dan Williams
2018-09-25 20:17     ` Dan Williams
2018-10-09 15:36   ` David Howells
2018-10-09 15:36     ` David Howells
2018-09-06  9:19 ` [PATCH 11/11] UAPI: Check headers build for C++ " David Howells
2018-09-10 16:26   ` kbuild test robot
2018-09-10 16:26     ` kbuild test robot
2018-09-10 16:26     ` kbuild test robot
2018-09-10 17:02   ` kbuild test robot
2018-09-10 17:02     ` kbuild test robot
2018-09-10 17:02     ` kbuild test robot
2018-09-14  9:10   ` Arnd Bergmann
  -- strict thread matches above, loose matches on Subject: below --
2018-09-05 15:54 [RFC] UAPI: Check headers by compiling all together as C++ David Howells
2018-09-05 15:54 ` David Howells
2018-09-05 15:54 ` David Howells
2018-09-05 15:54 ` David Howells
2018-09-05 15:54 ` David Howells
2018-09-05 15:54 ` [PATCH 01/11] UAPI: drm: Fix use of C++ keywords as structural members David Howells
2018-09-05 15:54   ` David Howells
2018-09-05 15:54 ` [PATCH 02/11] UAPI: keys: " David Howells
2018-09-05 15:54   ` David Howells
2018-09-05 15:54 ` [PATCH 03/11] UAPI: virtio_net: " David Howells
2018-09-05 16:54   ` Greg KH
2018-09-05 16:54   ` Greg KH
2018-09-05 17:15   ` David Howells
2018-09-05 17:15   ` David Howells
2018-09-05 17:35   ` Michael S. Tsirkin
2018-09-05 17:35   ` Michael S. Tsirkin
2018-09-06  7:09   ` David Howells
2018-09-06  7:09   ` David Howells
2018-09-06 14:36     ` Michael S. Tsirkin
2018-09-06 14:36     ` Michael S. Tsirkin
2018-09-05 15:54 ` David Howells
2018-09-05 15:55 ` [PATCH 04/11] UAPI: bcache: Fix use of embedded flexible array David Howells
2018-10-02 14:52   ` Jan Engelhardt
2018-10-09 15:41   ` David Howells
2018-10-09 16:54     ` Jan Engelhardt
2018-09-05 15:55 ` [PATCH 05/11] UAPI: coda: Don't use internal kernel structs in UAPI David Howells
2018-09-05 16:54   ` Jan Harkes
2018-09-05 17:12   ` Yann Droneaud
2018-09-05 17:28     ` Jan Harkes
2018-09-05 17:28       ` Jan Harkes
2018-09-05 17:24   ` David Howells
2018-09-06  7:13   ` David Howells
2018-09-06 11:52     ` Yann Droneaud
2018-09-06 12:16       ` Jan Harkes
2018-09-06 12:16         ` Jan Harkes
2018-09-06 14:53     ` David Howells
2018-09-05 15:55 ` [PATCH 06/11] UAPI: netfilter: Fix symbol collision issues David Howells
2018-09-05 15:55 ` [PATCH 07/11] UAPI: nilfs2: Fix use of undefined byteswapping functions David Howells
2018-09-05 22:20   ` Al Viro
2018-09-05 15:55 ` [PATCH 08/11] UAPI: sound: Fix use of u32 and co. in UAPI headers David Howells
2018-09-05 15:55   ` David Howells
2018-09-06  5:59   ` Takashi Sakamoto
2018-09-06  5:59     ` Takashi Sakamoto
2018-09-06  8:17   ` David Howells
2018-09-05 15:55 ` [PATCH 09/11] UAPI: ndctl: Fix g++-unsupported initialisation in headers David Howells
2018-09-05 15:55   ` David Howells
2018-09-05 15:55   ` David Howells
2018-09-05 15:55 ` [PATCH 10/11] UAPI: ndctl: Remove use of PAGE_SIZE David Howells
2018-09-05 15:55   ` David Howells
2018-09-05 15:55 ` [PATCH 11/11] UAPI: Check headers build for C++ David Howells
2018-09-05 16:55 ` [RFC] UAPI: Check headers by compiling all together as C++ Greg KH
2018-09-05 16:55 ` Greg KH
2018-09-05 16:55   ` Greg KH
2018-09-05 16:55   ` Greg KH
2018-09-05 16:55   ` Greg KH
2018-09-05 17:33   ` Yann Droneaud
2018-09-05 17:33     ` Yann Droneaud
2018-09-05 17:33     ` Yann Droneaud
2018-09-05 17:33     ` Yann Droneaud
2018-09-05 17:42     ` Michael S. Tsirkin
2018-09-05 17:42     ` Michael S. Tsirkin
2018-09-05 17:42       ` Michael S. Tsirkin
2018-09-05 17:42       ` Michael S. Tsirkin
2018-09-05 17:42       ` Michael S. Tsirkin
2018-09-05 17:42       ` Michael S. Tsirkin
2018-09-05 17:42       ` Michael S. Tsirkin
2018-09-06  7:12     ` Yann Droneaud
2018-09-06  7:12       ` Yann Droneaud
2018-09-06  7:12       ` Yann Droneaud
2018-09-06  7:12       ` Yann Droneaud
2018-09-05 19:22   ` Jan Engelhardt
2018-09-05 19:22   ` Jan Engelhardt
2018-09-05 19:22     ` Jan Engelhardt
2018-09-05 19:22     ` Jan Engelhardt
2018-09-05 19:22     ` Jan Engelhardt
2018-09-05 17:50 ` David Howells
2018-09-05 17:50 ` David Howells
2018-09-05 17:50   ` David Howells

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