strncmp issue

[M. Warner Losh]

In message: <1240918262.85945.1.camel at buffy.york.ac.uk>
            Gavin Atkinson <gavin at freebsd.org> writes:
: 
: This probably belongs on the -arm list, which I'm CCing.
: 
: On Tue, 2009-04-28 at 15:22 +0530, Channa wrote:
: > Hi,
: > 
: > I am using the freebsd implementation of strncmp for ARM which is an
: > assembly implementation.
: > I have a small doubt, when i tested the strncmp by passing the third argument:
: > 'n' as -1 the return values is  '0' instead it should '-1'.
: > When the third argument  to strncmp is as below:
: > 
: > ret = strncmp("a","b",-1)

This is the same as strncnp("a", "b", UMAXINT) because the len
argument is "size_t" which is unsigned.

: > I think the assembly implementation in
: > src/lib/libc/arm/string/strncmp.S file needs
: > to be modified to take care of the above condition.
: > 
: > In the current implementation
: > /* if ((len - 1) < 0) return 0 */
: >         subs    r2, r2, #1
: >         movmi   r0, #0
: >         RETc(mi)
: > 
: > This should be changed to check as below
: > 
: > /* if ((len ) < 0) return 0 */
: > /* Assembly code here */
: > 
: > Could anyone help in solving the above issue.?

This is a bug in your code not in strncmp.

Warner



: > Thanks & Regards,
: > Channagoud
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