MESSAGE
| DATE | 2018-07-25 |
| FROM | valdis.kletnieks@vt.edu
|
| SUBJECT | Re: [Hangout - NYLXS] Need Suggestions
|
From hangout-bounces-at-nylxs.com Wed Aug 1 17:28:38 2018
Return-Path:
X-Original-To: archive-at-mrbrklyn.com
Delivered-To: archive-at-mrbrklyn.com
Received: from www2.mrbrklyn.com (www2.mrbrklyn.com [96.57.23.82])
by mrbrklyn.com (Postfix) with ESMTP id 1B44216113A;
Wed, 1 Aug 2018 17:28:34 -0400 (EDT)
X-Original-To: hangout-at-www2.mrbrklyn.com
Delivered-To: hangout-at-www2.mrbrklyn.com
Received: by mrbrklyn.com (Postfix, from userid 1000)
id CA96F161134; Wed, 1 Aug 2018 17:28:28 -0400 (EDT)
Resent-From: Ruben Safir
Resent-Date: Wed, 1 Aug 2018 17:28:28 -0400
Resent-Message-ID: <20180801212828.GA8690-at-www2.mrbrklyn.com>
Resent-To: hangout-at-mrbrklyn.com
X-Original-To: ruben-at-mrbrklyn.com
Delivered-To: ruben-at-mrbrklyn.com
Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147])
by mrbrklyn.com (Postfix) with ESMTP id 12A1B161132
for ; Wed, 25 Jul 2018 18:10:40 -0400 (EDT)
Received: from localhost ([::1] helo=shelob.surriel.com)
by shelob.surriel.com with esmtp (Exim 4.90_1)
(envelope-from )
id 1fiRzN-0002cS-Ud; Wed, 25 Jul 2018 18:10:33 -0400
Received: from omr1.cc.ipv6.vt.edu ([2607:b400:92:8300:0:c6:2117:b0e]
helo=omr1.cc.vt.edu)
by shelob.surriel.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256)
(Exim 4.90_1) (envelope-from ) id 1fiRzI-0002cM-GT
for Kernelnewbies-at-kernelnewbies.org; Wed, 25 Jul 2018 18:10:28 -0400
Received: from mr5.cc.vt.edu (mr5.cc.vt.edu
[IPv6:2607:b400:92:8400:0:72:232:758b])
by omr1.cc.vt.edu (8.14.4/8.14.4) with ESMTP id w6PMANVo032231
for ; Wed, 25 Jul 2018 18:10:27 -0400
Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com
[209.85.220.199])
by mr5.cc.vt.edu (8.14.7/8.14.7) with ESMTP id w6PMAIUj025227
for ; Wed, 25 Jul 2018 18:10:23 -0400
Received: by mail-qk0-f199.google.com with SMTP id o18-v6so7794330qko.21
for ; Wed, 25 Jul 2018 15:10:23 -0700 (PDT)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=1e100.net; s=20161025;
h=x-gm-message-state:sender:from:to:cc:subject:in-reply-to:references
:mime-version:content-transfer-encoding:date:message-id;
bh=/wbF2CPELvT2dox7wgo7M2A8nIH6dChoBvxqfdmo/Pc=;
b=JHvB3kvRLhXONoSuAo4vgKlM5hCNpGanuZFaaIjNr7ocn5XgMlVeFXhQIYVke/EK2S
XHa24LTCvN3w8r3Xakal7FnObTKDEOgJEFsjGbAAjXWPM/SCZT+aCgevOos7l/5Jzk6t
AIg/TCWNhDBr+JqLT9frlllcoLVOxeBMO/edeB0GpIORaW7d2xgE4bpCSPcPl8Ksy/Ug
H4olEBv+90w2O9v4ScJ+B2zr8HQgdj7sZ+mz9slJPWXY0S0xQwjpGWKfe6mUYM7moqO8
gqlVVnPGfCe359kp/FnLNluUbzoE3zE9/mUoBsu2THGwGGE4MjFMUbClQWi8UfgFjer1
/TQw==
X-Gm-Message-State: AOUpUlF/s2KJJ9x9/Wg6AhmEhiNAfnCp1JYNhLOB1U7JhTXM3MTSGu8O
yiyF7eg7WU6dqPxke5kjIkHoCtAiB/XTy2gkhdf7w2E+MLab3ucs+vkfZV7e0lT4FD2pT+OGW6v
mPBiBVSTevhM0Q37pCtUdET2BxFaC2VQujiTNKnM=
X-Received: by 2002:ac8:3f54:: with SMTP id
w20-v6mr21199076qtk.91.1532556618448;
Wed, 25 Jul 2018 15:10:18 -0700 (PDT)
X-Google-Smtp-Source: AAOMgpefdGzeAUOkJS9F8ZPj7nSmo50d2fmZF45ImSG3F99P6tnYR9UqwVMK2Iye8i8MaQOgSFHMVw==
X-Received: by 2002:ac8:3f54:: with SMTP id
w20-v6mr21199065qtk.91.1532556618226;
Wed, 25 Jul 2018 15:10:18 -0700 (PDT)
Received: from turing-police.cc.vt.edu (turing-police.cc.ipv6.vt.edu.
[2001:468:c80:2103:f21f:afff:fe0c:8ada])
by smtp.gmail.com with ESMTPSA id u21-v6sm10143917qka.88.2018.07.25.15.10.16
(version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256);
Wed, 25 Jul 2018 15:10:16 -0700 (PDT)
From: valdis.kletnieks-at-vt.edu
X-Google-Original-From: Valdis.Kletnieks-at-vt.edu
X-Mailer: exmh version 2.8.0 04/21/2017 with nmh-1.7+dev
To: Himanshu Jha
In-Reply-To: <20180725213727.GA9993-at-himanshu-Vostro-3559>
References:
<20180725213727.GA9993-at-himanshu-Vostro-3559>
Mime-Version: 1.0
Date: Wed, 25 Jul 2018 18:10:16 -0400
Message-ID: <203226.1532556616-at-turing-police.cc.vt.edu>
X-BeenThere: kernelnewbies-at-kernelnewbies.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Archive:
Content-Type: multipart/mixed; boundary="===============5311157160313286230=="
Cc: inventsekar , Athul Joy ,
Kernelnewbies-at-kernelnewbies.org
Subject: Re: [Hangout - NYLXS] Need Suggestions
X-BeenThere: hangout-at-nylxs.com
List-Id: NYLXS Tech Talk and Politics
List-Unsubscribe: ,
List-Post:
List-Help:
List-Subscribe: ,
Errors-To: hangout-bounces-at-nylxs.com
Sender: "Hangout"
--===============5311157160313286230==
Content-Type: multipart/signed; boundary="==_Exmh_1532556616_2847P";
micalg=pgp-sha1; protocol="application/pgp-signature"
Content-Transfer-Encoding: 7bit
--==_Exmh_1532556616_2847P
Content-Type: text/plain; charset=us-ascii
On Thu, 26 Jul 2018 03:07:27 +0530, Himanshu Jha said:
> Now, this part of section is really important and somehow if you think
> you really learnt C well in the course offered at University. Then
> please take a look at implicit conversions:
> https://en.cppreference.com/w/c/language/conversion
>
> assert(sizeof(int) > -1);
>
> That should be enough to shatter your confidence.
If you want your confidence shaken:
https://www.lysator.liu.se/c/duffs-device.html
Fortunately, most maintainers will frown on stuff like that unless there's
a *damned* good reason - and Tom Duff had a very good reason indeed.
(Intro-to-c pop quiz - why is strcpy() not usable here?)
gcc 8.1.1 will accept Tom's code (with 3 warnings due to it
being pre-ANSI C).
For those who took a class on compiler design, and *think* they
know how LALR parsers and that stuff works - Examine the lexical
nesting of that, and figure out how the devil the compiler doesn't
get indigestion.. :)
And the K&R book on C does successive trimming of an strcpy(),
and finishes with
void strcpy(char *a, *b) { while (*a++ = *b++); }
The thing that's actually used a lot in the Linux kernel that gives
a lot of C newcomers heartburn is the widespread use of
structures of function pointers.. For example, this from include/linux/fs.h:
struct lock_manager_operations {
int (*lm_compare_owner)(struct file_lock *, struct file_lock *);
unsigned long (*lm_owner_key)(struct file_lock *);
fl_owner_t (*lm_get_owner)(fl_owner_t);
void (*lm_put_owner)(fl_owner_t);
void (*lm_notify)(struct file_lock *); /* unblock callback */
int (*lm_grant)(struct file_lock *, int);
bool (*lm_break)(struct file_lock *);
int (*lm_change)(struct file_lock *, int, struct list_head *);
void (*lm_setup)(struct file_lock *, void **);
};
That's the structure definition. Novice challenge: Find one or more places
where this structure is initialized, and understand how and why that works.
--==_Exmh_1532556616_2847P
Content-Type: application/pgp-signature
-----BEGIN PGP SIGNATURE-----
Comment: Exmh version 2.8.0 04/21/2017
iQEVAwUBW1j1SI0DS38y7CIcAQJL5wf/RPsHWU7eYTa4PDeWvCjXiuPbK889Y1xE
6NW9dr+ckfmr2+Sxn0oUKXeexoSl63EBt4HcsWD8hkeCxdjg8Qa/H8bgOLAy7acN
75qsvUripBd1vo25LXJ4BL2KRRivhticQ0hJU9cRB+OHDIefFZ1hNZQv++IBnIYk
4LakqGf+c5078SKz8qag3Cj4eHg3ZqzZ3hsRf7C4mDxpRjAsFwi6Ut0D9vNjpDKZ
/X0s5vN/M5opoW9L6ky73quPB0W8HgFpu4/xB5xlgrZ/rBV8lJR0/y14jMUVyO1Q
eE3B6LbVar8P0X2zoN2Ic2XQH18YLGMDqM/epw1ChCHFF/qj6y3opw==
=SpHb
-----END PGP SIGNATURE-----
--==_Exmh_1532556616_2847P--
--===============5311157160313286230==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies-at-kernelnewbies.org
https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
--===============5311157160313286230==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
_______________________________________________
Hangout mailing list
Hangout-at-nylxs.com
http://lists.mrbrklyn.com/mailman/listinfo/hangout
--===============5311157160313286230==--
--===============5311157160313286230==
Content-Type: multipart/signed; boundary="==_Exmh_1532556616_2847P";
micalg=pgp-sha1; protocol="application/pgp-signature"
Content-Transfer-Encoding: 7bit
--==_Exmh_1532556616_2847P
Content-Type: text/plain; charset=us-ascii
On Thu, 26 Jul 2018 03:07:27 +0530, Himanshu Jha said:
> Now, this part of section is really important and somehow if you think
> you really learnt C well in the course offered at University. Then
> please take a look at implicit conversions:
> https://en.cppreference.com/w/c/language/conversion
>
> assert(sizeof(int) > -1);
>
> That should be enough to shatter your confidence.
If you want your confidence shaken:
https://www.lysator.liu.se/c/duffs-device.html
Fortunately, most maintainers will frown on stuff like that unless there's
a *damned* good reason - and Tom Duff had a very good reason indeed.
(Intro-to-c pop quiz - why is strcpy() not usable here?)
gcc 8.1.1 will accept Tom's code (with 3 warnings due to it
being pre-ANSI C).
For those who took a class on compiler design, and *think* they
know how LALR parsers and that stuff works - Examine the lexical
nesting of that, and figure out how the devil the compiler doesn't
get indigestion.. :)
And the K&R book on C does successive trimming of an strcpy(),
and finishes with
void strcpy(char *a, *b) { while (*a++ = *b++); }
The thing that's actually used a lot in the Linux kernel that gives
a lot of C newcomers heartburn is the widespread use of
structures of function pointers.. For example, this from include/linux/fs.h:
struct lock_manager_operations {
int (*lm_compare_owner)(struct file_lock *, struct file_lock *);
unsigned long (*lm_owner_key)(struct file_lock *);
fl_owner_t (*lm_get_owner)(fl_owner_t);
void (*lm_put_owner)(fl_owner_t);
void (*lm_notify)(struct file_lock *); /* unblock callback */
int (*lm_grant)(struct file_lock *, int);
bool (*lm_break)(struct file_lock *);
int (*lm_change)(struct file_lock *, int, struct list_head *);
void (*lm_setup)(struct file_lock *, void **);
};
That's the structure definition. Novice challenge: Find one or more places
where this structure is initialized, and understand how and why that works.
--==_Exmh_1532556616_2847P
Content-Type: application/pgp-signature
-----BEGIN PGP SIGNATURE-----
Comment: Exmh version 2.8.0 04/21/2017
iQEVAwUBW1j1SI0DS38y7CIcAQJL5wf/RPsHWU7eYTa4PDeWvCjXiuPbK889Y1xE
6NW9dr+ckfmr2+Sxn0oUKXeexoSl63EBt4HcsWD8hkeCxdjg8Qa/H8bgOLAy7acN
75qsvUripBd1vo25LXJ4BL2KRRivhticQ0hJU9cRB+OHDIefFZ1hNZQv++IBnIYk
4LakqGf+c5078SKz8qag3Cj4eHg3ZqzZ3hsRf7C4mDxpRjAsFwi6Ut0D9vNjpDKZ
/X0s5vN/M5opoW9L6ky73quPB0W8HgFpu4/xB5xlgrZ/rBV8lJR0/y14jMUVyO1Q
eE3B6LbVar8P0X2zoN2Ic2XQH18YLGMDqM/epw1ChCHFF/qj6y3opw==
=SpHb
-----END PGP SIGNATURE-----
--==_Exmh_1532556616_2847P--
--===============5311157160313286230==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies-at-kernelnewbies.org
https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
--===============5311157160313286230==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
_______________________________________________
Hangout mailing list
Hangout-at-nylxs.com
http://lists.mrbrklyn.com/mailman/listinfo/hangout
--===============5311157160313286230==--
|
|
