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Mention, along with the behavior of succeeding system calls, the 

normal behavior of succeeding library functions regarding errno.
(That is, they may leave arbitrary nonzero values in errno.)

Ok kleink@; related to PR lib/41567 as well as a recent thread on
tech-userlevel.
This commit is contained in:
dholland 2009-07-23 02:31:56 +00:00
parent 7982dc729e
commit 6687b6883d
1 changed files with 16 additions and 5 deletions
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21
lib/libc/sys/intro.2
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@ -1,4 +1,4 @@
.\" $NetBSD: intro.2,v 1.52 2009/06/02 13:15:41 pooka Exp $ .\" $NetBSD: intro.2,v 1.53 2009/07/23 02:31:56 dholland Exp $
.\" .\"
.\" Copyright (c) 1980, 1983, 1986, 1991, 1993 .\" Copyright (c) 1980, 1983, 1986, 1991, 1993
.\" The Regents of the University of California. All rights reserved. .\" The Regents of the University of California. All rights reserved.
@ -64,10 +64,17 @@ a \-1 and to take action accordingly.)
Successful calls never set Successful calls never set
.Va errno ; .Va errno ;
once set, it remains until another error occurs. once set, it remains until another error occurs.
It should only be examined after an error. It should only be examined after an error has been reported, because
Note that a number of system calls overload the meanings of these otherwise a leftover value from some previous error may be found
error numbers, and that the meanings must be interpreted according instead.
to the type and circumstances of the call. .Po
Many library functions that are not system calls also set
.Va errno
on return, in the same fashion.
In these cases a nonzero value may be left in
.Va errno
even upon successful return if some internal action failed.
.Pc
.Pp .Pp
The manual page for each system call will list some of the common The manual page for each system call will list some of the common
errno codes that system call can return, but that should not be errno codes that system call can return, but that should not be
@ -78,6 +85,10 @@ Documenting all the error codes that a system call can return in
a more specification-like manner would take more resources than a more specification-like manner would take more resources than
this project has available. this project has available.
.Pp .Pp
Note also that a number of system calls overload the meanings of these
error numbers, and that in these cases the meanings must be
interpreted according to the type and circumstances of the call.
.Pp
The following is a complete list of the errors and their The following is a complete list of the errors and their
names as given in names as given in
.Aq Pa errno.h . .Aq Pa errno.h .