[manual]: rawmemchr(3) and UB

[Alejandro Colomar <alx.manpages@gmail.com>]

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Hi,

I was reading rawmemchr(3), and found some funny text:

RETURN VALUE
        The  memchr()  and memrchr() functions return a pointer to the matching
        byte or NULL if the character does not occur in the given memory area.

        The rawmemchr() function returns a pointer to the matching byte, if one
        is found.  If no matching byte is found, the result is unspecified.


Of course, if the byte is not found, the result is not unspecified, but rather 
undefined, and a crash is very likely so maybe there's not even a result.  I 
thought this might be a thinko of the manual page, but the glibc manual seems to 
have similar text:


<https://www.gnu.org/software/libc/manual/html_mono/libc.html#index-rawmemchr>
"
The rawmemchr function exists for just this situation which is surprisingly 
frequent. The interface is similar to memchr except that the size parameter is 
missing. The function will look beyond the end of the block pointed to by block 
in case the programmer made an error in assuming that the byte c is present in 
the block. In this case the result is unspecified. Otherwise the return value is 
a pointer to the located byte.
"


That test can't be true, and the result of that function when there's no match 
can't be anything other than UB, and likely a crash.  Please fix the doc.

Cheers,

Alex
-- 
<http://www.alejandro-colomar.es/>

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