svn commit: r304928 - in head/lib/libc: amd64/sys i386/sys sys

[Andrey Chernov]

On 28.08.2016 2:03, Konstantin Belousov wrote:
>   Since ptrace(2) syscall can return -1 for non-error situations, libc
>   wrappers set errno to 0 before performing the syscall, as the service
>   to the caller.

Both C99 and POSIX directly prohibits any standard function to set errno
to 0. ptrace() should either choose other errno to indicate non-error
situation or change return -1 to something else.