[src/trunk]: src/share/man/man3 mention argument promotion and change example

[yamt <yamt%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/483992321a29
branches:  trunk
changeset: 535424:483992321a29
user:      yamt <yamt%NetBSD.org@localhost>
date:      Sun Aug 18 08:57:07 2002 +0000

description:
mention argument promotion and change example
as well.
from OpenBSD.

diffstat:

 share/man/man3/stdarg.3 |  41 ++++++++++++++++++++++++++++++++---------
 1 files changed, 32 insertions(+), 9 deletions(-)

diffs (86 lines):

diff -r 5ddd5eb000ff -r 483992321a29 share/man/man3/stdarg.3
--- a/share/man/man3/stdarg.3   Sun Aug 18 08:03:35 2002 +0000
+++ b/share/man/man3/stdarg.3   Sun Aug 18 08:57:07 2002 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: stdarg.3,v 1.14 2002/02/13 08:17:30 ross Exp $
+.\"    $NetBSD: stdarg.3,v 1.15 2002/08/18 08:57:07 yamt Exp $
 .\"
 .\" Copyright (c) 1990, 1991, 1993
 .\"    The Regents of the University of California.  All rights reserved.
@@ -37,7 +37,7 @@
 .\"
 .\"    @(#)stdarg.3    8.1 (Berkeley) 6/5/93
 .\"
-.Dd April 14, 2001
+.Dd August 18, 2002
 .Dt STDARG 3
 .Os
 .Sh NAME
@@ -131,6 +131,25 @@
 (as promoted according to the default argument promotions),
 random errors will occur.
 .Pp
+If the type in question is one that gets promoted, the promoted type
+should be used as the argument to
+.Fn va_arg .
+The following describes which types are promoted (and to what):
+.Bl -dash -compact
+.It
+.Va short
+is promoted to
+.Va int
+.It
+.Va float
+is promoted to
+.Va double
+.It
+.Va char
+is promoted to
+.Va int
+.El
+.Pp
 The first use of the
 .Fn va_arg
 macro after that of the
@@ -170,18 +189,20 @@
 macro returns no value.
 .Sh EXAMPLES
 The function
-.Em foo
+.Fn foo
 takes a string of format characters and prints out the argument
 associated with each format character based on the type.
 .Bd -literal -offset indent
-void foo(char *fmt, ...)
+void
+foo(char *fmt, ...)
 {
        va_list ap;
-       int d;
-       char c, *p, *s;
+       int d, c;
+       char *s;
+       double f;
 
        va_start(ap, fmt);
-       while (*fmt) {
+       while (*fmt)
                switch (*fmt++) {
                case 's':                       /* string */
                        s = va_arg(ap, char *);
@@ -192,11 +213,13 @@
                        printf("int %d\en", d);
                        break;
                case 'c':                       /* char */
-                       c = va_arg(ap, char);
+                       c = va_arg(ap, int);    /* promoted */
                        printf("char %c\en", c);
                        break;
+               case 'f':                       /* float */
+                       f = va_arg(ap, double); /* promoted */
+                       printf("float %f\en", f);
                }
-       }
        va_end(ap);
 }
 .Ed