Re: [PATCH 3/6] test: Add a test for strim()

[Tom Rini <trini@konsulko.com>]

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On Wed, Mar 19, 2025 at 12:59:05PM +0100, Simon Glass wrote:

> This function trims whitespace from the start and end of a string. Add a
> test for it.
> 
> Signed-off-by: Simon Glass <sjg@chromium.org>
> ---
> 
>  test/lib/string.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)

This got me to ask "What even is using strim and where did it come
from?". To which the answer is:
- A few places, but it's probably reasonable.
- Linux, pre-2011.

I say the latter because we're missing a bug fix to the strim function
that's been there since 2011:

commit 66f6958e69d8055277356d3cc2e7a1d734db1755
Author: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Date:   Mon Oct 31 17:12:37 2011 -0700

    lib/string.c: fix strim() semantics for strings that have only blanks
    
    Commit 84c95c9acf0 ("string: on strstrip(), first remove leading spaces
    before running over str") improved\x7f 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.
    
    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
    
    The patch restores the old strim() semantics.
    
    Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
    Cc: Andre Goddard Rosa <andre.goddard@gmail.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

-- 
Tom

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