Message-ID: <536E6070.3030904@infradead.org>
Date:	Sat, 10 May 2014 10:22:56 -0700
From:	Randy Dunlap <rdunlap@...radead.org>
To:	George Spelvin <linux@...izon.com>, tj@...nel.org
CC:	akpm@...ux-foundation.org, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org, mingo@...hat.com,
	torvalds@...ux-foundation.org
Subject: Re: [PATCH 1/2] Add lib/glob.c

On 05/10/2014 07:03 AM, George Spelvin wrote:
> Thanks a lot for the feedback!
> 
>> On Fri, May 09, 2014 at 11:13:56PM -0400, George Spelvin wrote:
>>> +/**
>>> + * glob_match - Shell-style pattern matching, like !fnmatch(pat, str, 0)
>>> + * @pat: Pattern to match.  Metacharacters are ?, *, [ and \.
>>> + *       (And, inside character classes, !, - and ].)
> 
>> @ARG lines should be contained in a single line.  Just "Pattern to
>> match." should do.  With detailed description in the body.

That's old/historical, not current.

> Huh, Documentation/kernel-doc-nano-HOWTO.txt (lines 57-59, to be precise)
> implies otherwise pretty strongly.  But I can certainly change it.

Either way should be OK.

>> Just adding glob.o to lib-y should be enough.  It will be excluded
>> from linking if unused.
> 
> Will that work right if the caller is a module?  What will it get linked
> into, the main kernel binary or the module?

and sometimes we have to use obj-y instead of lib-y.

> A significant and very helpful simplification; I just want to be sure
> it works right.
> 
>>> +#ifdef UNITTEST
>>> +/* To do a basic sanity test, "cc -DUNITTEST glob.c" and run a.out. */
>>> +
>>> +#include <stdbool.h>
>>> +#define __pure __attribute__((pure))
>>> +#define NOP(x)
>>> +#define EXPORT_SYMBOL NOP	/* Two stages to avoid checkpatch complaints */
> 
>> These things tend to bitrot.  Let's please keep testing harness out of
>> tree.
> 
> Damn, when separated it bitrots a lot faster.  That's *is* my testing
> harness, and I wanted to keep it close so it has a chance on hell of
> being used by someone who updates it.
> 
> Especially given that the function's interface is quite rigidly defined,
> do you really think there will be a lot of rot?
> 
>> Do we make library routines separate modules usually?
> 
> A large number of files in lib/ are implemented that way (lib/crc-ccitt.c,
> just for one example), and that's what I copied.  But if I just do the
> obj-y thing, all that goes away
> 
>>> +bool __pure
>>> +glob_match(char const *pat, char const *str)
>>
>> The whole thing fits in a single 80 column line, right?
>>
>> bool __pure glob_match(char const *pat, char const *str)
> 
> Whoops, a residue of my personal code style.  (I like to left-align
> function names in definitions so they're easy to search for with ^func.)
> But it's not kernel style.  Will fix.
> 
>>> +{
>>> +	/*
>>> +	 * Backtrack to previous * on mismatch and retry starting one
>>> +	 * character later in the string.  Because * matches all characters
>>> +	 * (no exception for /), it can be easily proved that there's
>>> +	 * never a need to backtrack multiple levels.
>>> +	 */
>>> +	char const *back_pat = 0, *back_str = back_str;
> 
>> Blank line here.
> 
> I had considered the "/*" start of the following block comment as visually
> enough separation between variable declarations and statements, but sure,
> I can add one.
> 
>> I haven't delved into the actual implementation.  Looks sane on the
>> first glance.
> 
> That's the part I'm least worried about, actually.
> 
>> Again, I don't really think the userland testing code belongs here.
>> If you want to keep them, please make it in-kernel selftesting.  We
>> don't really want to keep code which can't get built and tested in
>> kernel tree proper.
> 
> I'll see if I can figure out how to do that.  Simple as it is, I hate to
> throw away regression tests.


-- 
~Randy
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