lkml.org 
[lkml]   [2011]   [Oct]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Fix strim() semantics for strings that have only blanks
On Wed, 12 Oct 2011 10:31:57 +0200
Michael Holzheu <holzheu@linux.vnet.ibm.com> wrote:

> Hello Andre,
>
> With git commit 84c95c9acf088c99d8793d78036b67faa5d0b851 a patch from
> you went upstream where you wanted to improve the performance of the
> strim() function.
>
> Unfortunately this changed the semantics of strim() and broke my code. Before
> the patch it was possible to use strim() without using the return value for
> removing trailing spaces from strings that had either only blanks or only
> trailing blanks.
>
> Now this does not work any longer for strings that *only* have blanks.
>
> Before patch: " " -> "" (empty string)
> After patch: " " -> " " (no change)
>
> I think we should remove your patch to restore the old behavior.
>
> >From the description (lib/string.c):
>
> * Note that the first trailing whitespace is replaced with a %NUL-terminator
>
> => The first trailing whitespace of a string that only has whitespace
> characters is the first whitespace

Yes, that change makes sense.

> Also strim() explicitly does not have "__must_check", in order to use it
> without using the return value.
>

This observation seems to have nothing to do with the patch?

I think that strim() _should_ have __must_check annotation (which means
that strim() simply disappears, which is good). It is only safe to
ignore the strim() return value if the caller knows that the string
started with a non-space. The number of situations where this is
guaranteed are faily small, I suspect. Whereas the chances of someone
screwing this up are pretty high :(




\
 
 \ /
  Last update: 2011-10-14 01:57    [W:0.027 / U:0.424 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site