Re: FYI: devel/kyua 14 failures for head -r338518M based build in a Pine64+ 2GB (aarch64 / cortexA53 / A64) context

On 2018-Sep-16, at 1:50 PM, Jilles Tjoelker <jilles at stack.nl> wrote:

> On Sun, Sep 16, 2018 at 01:21:33PM -0700, Mark Millard wrote:
>> On 2018-Sep-16, at 10:50 AM, Jilles Tjoelker <jilles at stack.nl> wrote:
> 
>>> On another note, the comment just below that,
> 
>>>       /* But we need to zero-extend (char is unsigned) the value and then
>>>          perform a signed 32-bit subtraction.  */
> 
>>> shows a wrong reason for doing the right thing since memcmp (as well as
>>> strcmp and strncmp) are defined to compare based on unsigned chars,
>>> regardless of the signedness of char.
> 
>> Ahh, standard are so much fun: there are so many to choose from.
> 
>> I looked up ISO/IEC 9899:2011 (E) and its 7.24.4.1 "The memcmp function".
>> It makes no such explicit claim about using using unsigned chars for
>> the comparison standard:
> 
>> QUOTE of the Description part:
>> The memcmp function compares the first n characters of the object pointed
>> by s1 to the first n characters of the object pointed by s2.
>> END QUOTE
> 
>> QUOTE of the Returns part:
>> The memcmp function returns an integer greater than, equal to, or less
>> than zero, accordingly as the object pointed to by s1 is greater than,
>> equal to, or less than the object pointed to by s2.
>> END QUOTE
> 
>> If I had to guess the intent of "characters" would be based on the
>> char type for C11. I did not find anything about the issue in the C99
>> rationale that I also happen to have available to look at.
> 
> In C99, C11 and C17, the text about using unsigned chars is under
> "Comparison functions" and it applies to memcmp, strcmp and strncmp
> (which are documented together in the section).
> 
>> For all I know, POSIX or other standards may be more explicit and not
>> agree.
> 
> POSIX does not document memcmp, strcmp and strncmp close together and
> copies the text about using unsigned chars to each of them. This means
> that it agrees with the C standards.
> 

Thanks for noting the factored-out material in the C11 standard. Sorry
for the noise of missing that factorization when I looked up memcmp.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)