Re: sed in CURRENT fails in textproc/jq

Warner Losh <imp@bsdimp.com> writes:
> As for memchr, https://pubs.opengroup.org/onlinepubs/009696799/functions/memchr.html
> has no such permission to examine 'the entire buffer at once' nor any restirction
> as to the length extending beyond the address space. I'm skeptical of your reading
> that it allows one to examine all of [b, b + len), so please explain where the standard
> supports reading past the first occurance.

C11 says:

    (7.24.4.1 §2) The memcmp function compares the first n characters of
    the object pointed to by s1 to the first n characters of the object
    pointed to by s2.

and

    (7.24.5.1 §2) The memchr function locates the first occurrence of c
    (converted to an unsigned char) in the initial n characters (each
    interpreted as unsigned char) of the object pointed to by s. The
    implementation shall behave as if it reads the characters
    sequentially and stops as soon as a matching character is found.

The second sentence in the description of memchr() means a bogus length
is allowed as long as we get a match before we read past the end of the
object.  There is no such provision for memcmp(), so calling memcmp()
with a bogus length invokes UB.

DES
-- 
Dag-Erling Smørgrav - des@FreeBSD.org