standard error handling for malloc() broken for user root and group wheel

User root and group wheel cannot get standard error handling for malloc()
even if they specifically asked for it using MALLOC_OPTIONS=a or
equivalent.  This was broken in rev.1.73 of malloc.c.  Fix:

%%%
Index: malloc.c
===================================================================
RCS file: /home/ncvs/src/lib/libc/stdlib/malloc.c,v
retrieving revision 1.84
diff -u -2 -r1.84 malloc.c
--- malloc.c	28 Nov 2003 18:03:22 -0000	1.84
+++ malloc.c	16 Feb 2004 18:38:36 -0000
_at__at_ -411,5 +411,5 _at__at_
     const char *p;
     char b[64];
-    int i, j;
+    int i, j, malloc_a;
     int save_errno = errno;

_at__at_ -420,4 +420,5 _at__at_
 #endif /* MALLOC_EXTRA_SANITY */

+    malloc_a = 0;
     for (i = 0; i < 3; i++) {
 	if (i == 0) {
_at__at_ -438,6 +439,6 _at__at_
 		case '>': malloc_cache   <<= 1; break;
 		case '<': malloc_cache   >>= 1; break;
-		case 'a': malloc_abort   = 0; break;
-		case 'A': malloc_abort   = 1; break;
+		case 'a': malloc_abort   = 0; malloc_a = 1; break;
+		case 'A': malloc_abort   = 1; malloc_a = 0; break;
 #if defined(MADV_FREE)
 		case 'h': malloc_hint    = 0; break;
_at__at_ -469,9 +470,16 _at__at_

     /*
-     * Sensitive processes, somewhat arbitrarily defined here as setuid,
-     * setgid, root and wheel cannot afford to have malloc mistakes.
+     * Sensitive processes, somewhat arbitrarily defined here as setuid
+     * and setgid ones, cannot afford to have malloc mistakes.
      */
-    if (issetugid() || getuid() == 0 || getgid() == 0)
-	    malloc_abort = 1;
+    if (issetugid())
+	malloc_abort = 1;
+
+    /*
+     * Also, abort on malloc mistakes for root and wheel unless the user
+     * has explicitly asked not to.
+     */
+    if (malloc_a == 0 && (getuid() == 0 || getgid() == 0))
+	malloc_abort = 1;

     UTRACE(0, 0, 0);
%%%

Related unfixed bugs:
- the special handling for sensitive processes is not documented in malloc.3.
- the special handling for sensitive processes doesn't work in all cases.
  Processes may become sensitive after malloc() has been initialized.
- the special handling for sensitive processes is not in RELENG_4.  This is
  only a bug if the special handling is not a bug.

Bruce