[Bug libc/16885] New: strcmp() on sparc64 can return wrong result

["baggett.patrick at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=16885

            Bug ID: 16885
           Summary: strcmp() on sparc64 can return wrong result
           Product: glibc
           Version: 2.18
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: baggett.patrick at gmail dot com
                CC: drepper.fsp at gmail dot com

In 2011, strcmp() was rewritten for sparc64 to be faster in
ad69cc2652c0422ebac3296d914c25e470498ce1 by David S. Miller. However, there is
a particularly strange case where it can return the wrong value: if the bytes
after the last bytes being compared are both zero.

e.g.

char a[2] = { 0, 0 };
char b[2] = { 1, 0 };

printf("%d", strcmp(a,b));

This should print "-1" because the first byte differs by 1. The second byte
should not be examined. However, it erroneously prints "0". Changing either
a[1] or b[1] to a non-zero value causes the "-1" to be correctly returned. For
example, this returns the correct value of -1:

char a[2] = { 0, 0xaa };
char b[2] = { 1, 0 };

printf("%d", strcmp(a,b));

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