Re: Problem with running tests during installing coreutils-5.94

[Paul Eggert]

I've long been suspicious of the 'alloca' inside shred.c.  Can you
please apply the patch at the end of this message?  (Save this email
into a file FOO, and then type "patch shred.c <FOO"; you'll get minor
complaints about line numbers that you can ignore.)

If this doesn't fix your problem, please try putting a "return;"
statement at the top of the direct_mode function, so that direct_mode
is a no-op.

Thanks.

I installed the following patch into CVS coreutils, since that alloca
is kind of dicey anyway.

2006-04-18  Paul Eggert  <address@hidden>

        * src/shred.c (fillrand): The assertion was way too weak, due to
        what must be a typo.  Strengthen it to its intended value.
        (dopass): Don't use alloca; it's not worth the aggravation here,
        since it's used only to get a page-aligned buffer, and page
        alignment doesn't buy us much here.  I'm suspicious that alloca
        causes problems on some hosts, due to a recent bug report by Adam
        Waltman.

--- src/shred.c 26 Mar 2006 12:07:59 -0000      1.123
+++ src/shred.c 19 Apr 2006 06:27:43 -0000      1.124
@@ -321,10 +321,10 @@ fillpattern (int type, unsigned char *r,
 static void
 fillrand (struct isaac_state *s, uint32_t *r, size_t size_max, size_t size)
 {
-  size = (size + ISAAC_BYTES - 1) / ISAAC_BYTES;
-  assert (size <= size_max);
+  size_t refills = (size + ISAAC_BYTES - 1) / ISAAC_BYTES;
+  assert (refills * ISAAC_BYTES <= size_max);
 
-  while (size--)
+  while (refills--)
     {
       isaac_refill (s, r);
       r += ISAAC_WORDS;
@@ -428,9 +428,7 @@ dopass (int fd, char const *qname, off_t
   size_t lim;                  /* Amount of data to try writing */
   size_t soff;                 /* Offset into buffer for next write */
   ssize_t ssize;               /* Return value from write */
-  uint32_t *r;                 /* Fill pattern.  */
-  size_t rsize = 3 * MAX (ISAAC_WORDS, 1024) * sizeof *r; /* Fill size.  */
-  size_t ralign = lcm (getpagesize (), sizeof *r); /* Fill alignment.  */
+  uint32_t r[3 * MAX (ISAAC_WORDS, 1024)];  /* Fill pattern.  */
   char pass_string[PASS_NAME_SIZE];    /* Name of current pass */
   bool write_error = false;
   bool first_write = true;
@@ -445,13 +443,10 @@ dopass (int fd, char const *qname, off_t
       return -1;
     }
 
-  r = alloca (rsize + ralign - 1);
-  r = ptr_align (r, ralign);
-
   /* Constant fill patterns need only be set up once. */
   if (type >= 0)
     {
-      lim = rsize;
+      lim = sizeof r;
       if ((off_t) lim > size && size != -1)
        {
          lim = (size_t) size;
@@ -476,7 +471,7 @@ dopass (int fd, char const *qname, off_t
   for (;;)
     {
       /* How much to write this time? */
-      lim = rsize;
+      lim = sizeof r;
       if ((off_t) lim > size - offset && size != -1)
        {
          if (size < offset)
@@ -486,7 +481,7 @@ dopass (int fd, char const *qname, off_t
            break;
        }
       if (type < 0)
-       fillrand (s, r, rsize, lim);
+       fillrand (s, r, sizeof r, lim);
       /* Loop to retry partial writes. */
       for (soff = 0; soff < lim; soff += ssize, first_write = false)
        {