Re: [patch] memset.c: Make memset safe even if sizeof (int) = 2.

[Kazu Hirata <kazu at cs dot umass dot edu>]

Hi Christopher,

> This looks like a good catch, but the usual idiom for this is to do
> something like:
> 
>            unsigned int d = c & 0xff;
> 
> to insure that there is no sign extension.
> 
> If you agree with this, then feel free to check in a variation on your
> below patch.  Btw, could you fix the ChangeLog?  It seems to have a
> typo "sizeof (2) = 2".

Thanks.  I checked in the following.

2002-11-25  Kazu Hirata  <kazu@cs.umass.edu>

	* libc/string/memset.c (memset): Make it safe even if
	sizeof (int) = 2.

Index: memset.c
===================================================================
RCS file: /cvs/src/src/newlib/libc/string/memset.c,v
retrieving revision 1.2
diff -u -r1.2 memset.c
--- memset.c	24 Aug 2000 16:25:36 -0000	1.2
+++ memset.c	25 Nov 2002 20:52:51 -0000
@@ -64,21 +64,23 @@
     {
       /* If we get this far, we know that n is large and m is word-aligned. */
 
+      /* To avoid sign extention, copy C to an unsigned variable.  */
+      unsigned int d = c & 0xff;
+
       aligned_addr = (unsigned long*)m;
 
-      /* Store C into each char sized location in BUFFER so that
+      /* Store D into each char sized location in BUFFER so that
          we can set large blocks quickly.  */
-      c &= 0xff;
       if (LBLOCKSIZE == 4)
         {
-          buffer = (c << 8) | c;
+          buffer = (d << 8) | d;
           buffer |= (buffer << 16);
         }
       else
         {
           buffer = 0;
           for (i = 0; i < LBLOCKSIZE; i++)
-	    buffer = (buffer << 8) | c;
+	    buffer = (buffer << 8) | d;
         }
 
       while (n >= LBLOCKSIZE*4)