Revert r206649.

Simplify the presented declaration of struct sigaction, noting the
caveat in the text. Real layout of the structure and exposed
implementation namespace only obfuscates the usage.

Submitted by:	bde
MFC after:	3 days

1 files changed, 13 insertions, 18 deletions

diff --git a/lib/libc/sys/sigaction.2 b/lib/libc/sys/sigaction.2
index 51b6c47..3b4f2f0 100644
--- a/lib/libc/sys/sigaction.2
+++ b/lib/libc/sys/sigaction.2
@@ -28,7 +28,7 @@
 .\"	From: @(#)sigaction.2	8.2 (Berkeley) 4/3/94
 .\" $FreeBSD$
 .\"
-.Dd April 13, 2010
+.Dd April 18, 2010
 .Dt SIGACTION 2
 .Os
 .Sh NAME
@@ -40,16 +40,11 @@
 .In signal.h
 .Bd -literal
 struct  sigaction {
-        union {
-                void    (*__sa_handler)(int);
-                void    (*__sa_sigaction)(int, siginfo_t *, void *);
-        } __sigaction_u;                /* signal handler */
+        void    (*sa_handler)(int);
+        void    (*sa_sigaction)(int, siginfo_t *, void *);
         int     sa_flags;               /* see signal options below */
         sigset_t sa_mask;               /* signal mask to apply */
 };
-
-#define	sa_handler	__sigaction_u.__sa_handler
-#define	sa_sigaction	__sigaction_u.__sa_sigaction
 .Ed
 .Ft int
 .Fo sigaction
@@ -148,6 +143,16 @@ If
 is non-zero, the previous handling information for the signal
 is returned to the user.
 .Pp
+The above declaration of
+.Vt "struct sigaction"
+is not literal.
+It is provided only to list the accessible members.
+See
+.In sys/signal.h
+for the actual definition.
+In particular, the storage occupied by sa_handler and sa_sigaction overlaps,
+and an application can not use both simultaneously.
+.Pp
 Once a signal handler is installed, it normally remains installed
 until another
 .Fn sigaction
@@ -496,16 +501,6 @@ or
 .Dv SIG_IGN
 this way.
 .Pp
-If preprocessing symbol
-.Va _POSIX_C_SOURCE
-with the value >= 199309 is not defined, the following declaration for
-the handler shall be used:
-.Bl -tag -offset indent -width short
-.It Tn POSIX Dv SA_SIGINFO :
-.Ft void
-.Fn handler int "struct __sigaction *" "void *" ;
-.El
-.Pp
 If the
 .Dv SA_SIGINFO
 flag is not set, the handler function should match