xv6

commit 40884996414a0b5bacdf306a98531f55cebdfbfe
parent 3994dade649dba764fdab1b8660ef609ab373fc9
Author: Brian Swetland <swetland@frotz.net>
Date:   Sun, 29 Dec 2013 09:44:41 -0800

update printf() and cprintf() to use stdarg.h

Rolling your own stdarg stuff is cute, but AMD64 passes the first six parameters
via registers, using al as a count, etc.  Better to trust the toolchain to get
it right.

Diffstat:
M
kernel/console.c
 | 
13
++++++++-----
M
ulib/printf.c
 | 
18
++++++++----------

2 files changed, 16 insertions(+), 15 deletions(-)
diff --git a/kernel/console.c b/kernel/console.c
@@ -2,6 +2,8 @@
 // Input is from the keyboard or serial port.
 // Output is written to the screen and serial port.
 
+#include <stdarg.h>
+
 #include "types.h"
 #include "defs.h"
 #include "param.h"
@@ -53,10 +55,12 @@ printint(int xx, int base, int sign)
 void
 cprintf(char *fmt, ...)
 {
+  va_list ap;
   int i, c, locking;
-  uint *argp;
   char *s;
 
+  va_start(ap, fmt);
+
   locking = cons.locking;
   if(locking)
     acquire(&cons.lock);
@@ -64,7 +68,6 @@ cprintf(char *fmt, ...)
   if (fmt == 0)
     panic("null fmt");
 
-  argp = (uint*)(void*)(&fmt + 1);
   for(i = 0; (c = fmt[i] & 0xff) != 0; i++){
     if(c != '%'){
       consputc(c);
@@ -75,14 +78,14 @@ cprintf(char *fmt, ...)
       break;
     switch(c){
     case 'd':
-      printint(*argp++, 10, 1);
+      printint(va_arg(ap, int), 10, 1);
       break;
     case 'x':
     case 'p':
-      printint(*argp++, 16, 0);
+      printint(va_arg(ap, int), 16, 0);
       break;
     case 's':
-      if((s = (char*)*argp++) == 0)
+      if((s = va_arg(ap, char*)) == 0)
         s = "(null)";
       for(; *s; s++)
         consputc(*s);
diff --git a/ulib/printf.c b/ulib/printf.c
@@ -1,3 +1,5 @@
+#include <stdarg.h>
+
 #include "types.h"
 #include "stat.h"
 #include "user.h"
@@ -39,12 +41,12 @@ printint(int fd, int xx, int base, int sgn)
 void
 printf(int fd, char *fmt, ...)
 {
+  va_list ap;
   char *s;
   int c, i, state;
-  uint *ap;
+  va_start(ap, fmt);
 
   state = 0;
-  ap = (uint*)(void*)&fmt + 1;
   for(i = 0; fmt[i]; i++){
     c = fmt[i] & 0xff;
     if(state == 0){
@@ -55,14 +57,11 @@ printf(int fd, char *fmt, ...)
       }
     } else if(state == '%'){
       if(c == 'd'){
-        printint(fd, *ap, 10, 1);
-        ap++;
+        printint(fd, va_arg(ap, int), 10, 1);
       } else if(c == 'x' || c == 'p'){
-        printint(fd, *ap, 16, 0);
-        ap++;
+        printint(fd, va_arg(ap, int), 16, 0);
       } else if(c == 's'){
-        s = (char*)*ap;
-        ap++;
+        s = va_arg(ap, char*);
         if(s == 0)
           s = "(null)";
         while(*s != 0){
@@ -70,8 +69,7 @@ printf(int fd, char *fmt, ...)
           s++;
         }
       } else if(c == 'c'){
-        putc(fd, *ap);
-        ap++;
+        putc(fd, va_arg(ap, uint));
       } else if(c == '%'){
         putc(fd, c);
       } else {