On Mon, Aug 29, 2016 at 09:16:29PM +0300, Andrey Chernov wrote: > Previous text is documented everywhere and describing usual good > practice, so it should remains in place, in that means r304928 should be > reverted, because replace proper way of doing things with obsoleted > feature description. > > What I suggest is not _replace_ old text with new, but _add_ new text as > describing current and not recommended way, with the direct mention that > this feature is obsoleted and not recommended for relay on it. >
diff --git a/lib/libc/sys/ptrace.2 b/lib/libc/sys/ptrace.2 index 48802f4..d406efc 100644 --- a/lib/libc/sys/ptrace.2 +++ b/lib/libc/sys/ptrace.2 @@ -2,7 +2,7 @@ .\" $NetBSD: ptrace.2,v 1.2 1995/02/27 12:35:37 cgd Exp $ .\" .\" This file is in the public domain. -.Dd August 28, 2016 +.Dd August 29, 2016 .Dt PTRACE 2 .Os .Sh NAME @@ -900,19 +900,29 @@ argument is ignored. .Pp Additionally, other machine-specific requests can exist. .Sh RETURN VALUES +Most requests return 0 on success and \-1 on error. Some requests can cause .Fn ptrace to return \-1 -as a non-error value; to disambiguate, +as a non-error value, among them are +.Dv PT_READ_I +and +.Dv PT_READ_D , +which return the value read from the process memory on success. +To disambiguate, .Va errno -is set to 0 in the libc wrapper for the -.Fn ptrace -system call and +can be set to 0 before the call and checked afterwards. +.Pp +Current .Fn ptrace -callers can reliably check +implementation always sets +.Va errno +to 0 before calling into kernel, both for historic reasons and for +consistency with other operating systems. +It is recommended to assign zero to .Va errno -for non-zero value afterwards. +explicitely for future compatibility. .Sh ERRORS The .Fn ptrace _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
