gawk 3.1.6: rand.awk test case alignment problem

[Duncan Moore]

Hi

I've sent this bug report to gnu.utils.bug twice recently (Feb 11, Jan 2), 
but now think this was the wrong address. There's been no response, so I'm 
now sending it here as well. My apologies if you've seen it before.


I've compiled gawk 3.1.6 on an ARM 710 platform using gcc 4.1.1, and running
the random number test case gawk-3.1.6/test/rand.awk:

BEGIN {
srand(2)
for (i = 0; i < 19; i++)
 printf "%3d ", (1 + int(100 * rand()))
    print ""
}

with 'gawk -f rand.awk', gives:

30   5  39  81  93  31  71  45  82  43  99  97 100  52  86  91  68  65  60

As I understand it, this is wrong, and the output should be identical on
every platform, since the RNG is built in to gawk. This is what should be
output:

62  67  88   6  35  77   3  68  30  96  90  26  35   8  88  93  49  53  37

The reason for the error, is that char array 'state' in builtin.c is not
word aligned, and it is cast to an int*. This causes problems on
architectures that require ints to be word aligned. There is a comment in
random.c that this causes bus errors on the Sparc platform, but the code
does not appear to have been fixed. Other platforms could be affected too.

A fix for this (which will not affect other platforms) is:

diff -u -p gawk-3.1.6/builtin.c gawk-3.1.6.ro2/builtin.c
--- gawk-3.1.6/builtin.c 2007-09-30 19:57:05 +0000
+++ gawk-3.1.6.ro2/builtin.c 2008-01-21 19:38:12 +0000
@@ -2027,14 +2027,16 @@ do_cos(NODE *tree)
/* do_rand --- do the rand function */

static int firstrand = TRUE;
-static char state[256];
+#define SIZEOF_STATE 256
+static uint32_t istate[SIZEOF_STATE/sizeof(uint32_t)];
+static char *const state = (char *const) istate;

/* ARGSUSED */
NODE *
do_rand(NODE *tree ATTRIBUTE_UNUSED)
{
 if (firstrand) {
-  (void) initstate((unsigned) 1, state, sizeof state);
+  (void) initstate((unsigned) 1, state, SIZEOF_STATE);
  /* don't need to srandom(1), initstate() does it for us. */
  firstrand = FALSE;
  setstate(state);
@@ -2057,7 +2059,7 @@ do_srand(NODE *tree)
 long ret = save_seed; /* SVR4 awk srand returns previous seed */

 if (firstrand) {
-  (void) initstate((unsigned) 1, state, sizeof state);
+  (void) initstate((unsigned) 1, state, SIZEOF_STATE);
  /* don't need to srandom(1), we're changing the seed below */
  firstrand = FALSE;
  (void) setstate(state);

The rand.awk test case then gives the same results as on other platforms.


As an aside, when trying to locate the problem I used -Wextra which gives
this warning (amongst others):

dfa.c: At top level:
dfa.c:762: warning: missing initializer
dfa.c:762: warning: (near initialization for 'prednames[12].pred')

This turned out to be a red-herring. I think the following change may better
reflect what the compiler actually produces, and what the programmer
intended. (It's some time now since I looked at this, but I think that the
search of the array can't run off the end.)

--- gawk-3.1.6/dfa.c            2007-09-03 03:30:12 +0000
+++ gawk-3.1.6.ro2/dfa.c        2008-01-02 14:22:54 +0000
@@ -759,7 +759,6 @@ static struct {
  { ":graph:]", is_graph },
  { ":cntrl:]", is_cntrl },
  { ":blank:]", is_blank },
-  { 0 }
};


Regards

Duncan Moore